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1
Patrick, David A. "The Effects of Forest Practices on a Maine Amphibian Community." Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/PatrickDA2007.pdf.
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Hopkins, Samantha. "Chytridiomycosis in amphibian populations in the Western Cape, South Africa." Thesis, University of the Western Cape, 2002. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_7137_1359702947.
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There have been many cases reported of amphibian populations declining. These are often due to anthropogenic factors such as habitat destruction and pollution. However, some eclines have not had an obvious cause and many of these have been investigated and found to be due to pathogenic disease. Batrachochytrium dendrobatidis is a recently described pathogen of frogs. The population declines that have been associated with chytridiomycosis have occurred in relatively undisturbed areas such as national parks. The declines tend to occur at higher altitudes or in colder climates. This is thought to be because of the frog immune system being slower at lower temperatures. This project gives an overview of chytrid infection in the Western Cape and at a small number of sites in the Northern Cape and Eastern Cape.
3
Schneider, Amy Elizabeth. "Continued study of the use of created ponds for amphibian breeding in fragmented forested areas." [Huntington, WV : Marshall University Libraries], 2008. http://www.marshall.edu/etd/descript.asp?ref=876.
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Nowakowski, Aaron J. "Connectivity of fragmented amphibian populations in a Neotropical landscape." FIU Digital Commons, 2014. http://digitalcommons.fiu.edu/etd/1515.
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A high proportion of amphibian species are threatened with extinction globally, and habitat loss and degradation are the most frequently implicated causes. Rapid deforestation for the establishment of agricultural production is a primary driver of habitat loss in tropical zones where amphibian diversity is highest. Land-cover change affects native assemblages, in part, through the reduction of habitat area and the reduction of movement among remnant populations. Decreased gene flow contributes to loss of genetic diversity, which limits the ability of local populations to respond to further environmental changes. The focus of this dissertation is on the degree to which common land uses in Sarapiquí, Costa Rica impede the movement of two common amphibian species. First, I used field experiments, including displacement trials, and a behavioral landscape ecology framework to investigate the resistance of pastures to movement of Oophaga pumilio. Results from experiments demonstrate that pastures do impede movement of O. pumilio relative to forest. Microclimatic effects on movement performance as well as limited perceptual ranges likely contribute to reduced return rates through pastures. Next, I linked local processes to landscape scale estimates of resistance. I conducted experiments to measure habitat-specific costs to movement for O. pumilio and Craugastor bransfodrii, and then used experimental results to parameterize connectivity models. Model validation indicated highest support for resistance estimates generated from responses to land-use specific microclimates for both species and to predator encounters for O. pumilio. Finally, I used abundance and experiment-derived resistance estimates to analyze the effects of prevalent land uses on population genetic structure of the two focal species. While O. pumilio did not exhibit a strong response to landscape heterogeneity and was primarily structured by distances among sites, C. bransfordii genetic variation was explained by resistance estimates from abundance and experiment data. Collectivity, this work demonstrates that common land uses can offer different levels of resistance to amphibian movements in Sarapiquí and illustrates the value of investigating local scales processes to inform interpretation of landscape-scale patterns.
5
Bol, Leslie D. "Amphibian recruitment success at a landscape scale." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=78250.
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Size fluctuations in amphibian populations at single breeding sites are related to variations in recruitment from the larval stage. However, overall patterns of abundance should be related to the pattern of recruitment success at the many sites where breeding occurs over a landscape. Recruitment patterns for six amphibian species, Ambystoma laterale, A. maculatum, Bufo americanus, Hyla versicolor, Pseudacris crucifer and Rana sylvatica, were investigated at multiple sites within the 10 km 2 Mont St. Hilaire nature reserve during 2001 and 2002. Amphibians bred at eighteen sites but recruitment occurred at only 8 and 11 sites in each year, respectively. Hydroperiod and predation were the most important determinants of recruitment. Four species suffered multiple recruitment failures both years. However, when sites were considered collectively, recruitment was successful for all species because of asynchronous recruitment patterns across heterogeneous sites. Amphibian population dynamics may be stochastic at any single site but recruitment success at multiple sites is a plausible predictor of abundance and trends in regional population persistence.
6
Meyer, Shavonne. "Landscape history, dispersal, and the genetic structure of amphibian populations." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=101625.
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Habitat fragmentation can influence the genetics of a population through the direct loss of genetic diversity, and by the genetic processes that occur as a result of small remnant populations or the geographic isolation of populations. I examined the population genetics of two woodland amphibian species in localities with different land-use histories. The wood frog (Rana sylvatica) and the red-backed salamander (Plethodon cinereus) use the same general habitat but differ with respect to a few key life-history characteristics relating to dispersal. I then compared between species the relative influence each land-use scenario had on the population genetic structure. I found that habitat fragmentation affected the population genetics of the two amphibians and did so differently for each species. The differential population genetic response of these two amphibians to habitat fragmentation reinforces the important role of life-history characteristics in how the genetic structure of a population is shaped over time.
7
Strong, Becky. "Investigating the effects of organic pollutants on amphibian populations in the UK." Thesis, Lancaster University, 2016. http://eprints.lancs.ac.uk/82811/.
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Amphibians are undergoing dramatic population declines, with environmental pollution reported as a significant factor in such declines. Technologies are required that are able to monitor populations at risk of deteriorating environmental quality in a rapid, high-throughput and low-cost manner. The application of biospectroscopy in environmental monitoring represents such a scenario. Biospectroscopy is based on the vibrations of functional groups within biological samples and may be used to signature effects induced by chemicals in cells and tissues. Here, attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy in conjunction with multivariate analysis was implemented in order to distinguish between embryos, whole tadpoles at an early stage of development and individual tissues of late-stage tadpoles of the common frog collected from ponds in the UK with varying levels of water quality, due to contamination from both urban and agricultural sources. In addition, a Xenopus laevis cell line was exposed to low-levels of fungicides used in agriculture and assessed with ATR-FTIR spectroscopy. Embryos, in general did not represent a sensitive life stage for discriminating between ponds based on their infrared spectra. In contrast, tadpoles exposed to agricultural and urban pollutants, both at early and late stages of development were readily distinguished on the basis of their infrared spectra. ATR-FTIR spectroscopy also readily detected fungicideinduced changes in X.laevis cells, both as single-agent and binary mixture effects. Data reported in this study confirm the use of ATR-FTIR spectroscopy as a sensitive technique capable of detecting small changes in cellular groups, and as such represents a valuable starting point for its use in the monitoring of amphibian populations. However further research is needed in order to overcome confounding factors existent in natural populations of complex organisms.
8
Harpole, Douglas N. "Terrestrial Salamanders in southern Appalachain Harwood Forests: Relative Abundance, Nutritional Condition, and Response to Silvicultural Practices." Thesis, Virginia Tech, 1996. http://hdl.handle.net/10919/42710.
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We compared techniques for assessing nutritional condition in 3 groups of terrestrial salamanders. We measured variability in species richness and relative abundance before harvest at 5 sites in the Jefferson National Forest of southwest Virginia and compared the effects of 7 silvicultural treatments on terrestrial salamander richness and relative abundance at 1 site.Master of Science
9
Ma, Chui-ying, and 馬翠盈. "Assessment of the effects of agricultural practices on amphibian populations in Long Valley wetlands, Hong Kong." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B48199461.
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Agricultural practices have altered natural wetland habitats for thousands of years in lowland areas of Southeast Asia, and currently these highly modified wetlands constitute some of the most important remaining habitats for amphibians. However, decreasing area of arable land and increased use of chemicals may affect the persistence of lowland amphibian populations that are now dependent on these habitats. I investigated how amphibians responded to different kinds of farming treatments in a large agricultural wetland in Hong Kong.
In the first part of the study, I assessed the occurrence of breeding amphibians in 53 farming plots in 2010 and 2011. Anuran call surveys were conducted at night at the plots once a week from March to August for two years. Environmental variables were measured and used to develop models to examine species presence, occupancy, and detection probabilities. Wet agricultural plots supported 10 species of amphibians and all had detection probabilities of < 1 that varied seasonally and yearly. Organically managed plots and shallow water plots yielded high species richness and particularly attracted the ornate pygmy frog (Microhyla fissipes) and the paddy frog (Fejervarya limnocharis). Air temperature and humidity were the relatively consistent predictors that influenced calling activity of the four most commonly detected species (M. fissipes; F. limnocharis; brown tree frog Polypedates megacephalus; and G?nther’s frog Hylarana guentheri).
For the second part of the study, I assessed the impacts of fertilizers on amphibians. Using mesocosm experiments in the field, I compared the effects of a chemical fertilizer (granular urea) and an organic fertilizer (peanut cake) on the survival and growth of hatchlings of Polypedates megacephalus, the marbled pygmy frog (Microhyla pulchra), Asian common toad (Duttaphrynus melanostictus) and Chinese bullfrog (Hoplobatrachus rugulosus). Fertilizers were applied at low, manufacturer-recommended, and high levels, and survival and snout-vent-length were measured after 21 days. No individuals survived in the chemical fertilizer treatment at the recommended application level. Conversely, survival was high for P. megacephalus (96%), M. pulchra (54%) and D. melanostictus (90%), but relatively low for H. rugulosus (18%), at the recommended level of the organic fertilizer. P. megacephalus and M. pulchra tadpoles showed increased growth in elevated concentrations of organic fertilizer. Polypedates megacephalus tadpoles were 1.6 times longer in the low concentration and almost double in length in the high concentration treatments. Similarly, increased growth in M. pulchra in all organic treatments resulted in abbreviated time to metamorphosis. Chemical fertilizers are clearly detrimental to early life stages of these amphibians, but organic fertilizers may confer benefits including a shorter time to, and larger size at, metamorphosis.
These results suggest that where amphibian conservation is a priority, shifts in the management of wet agricultural crops and limiting the use of chemical fertilizers may increase the suitability of breeding habitats and survival at early life stages.published_or_final_version
Biological Sciences
Master
Master of Philosophy
10
Walker, Susan Frances. "Geographical patterns in the distribution of Batrachochytrium dendrobatidis and outbreaks of fatal chytridiomycosis in European amphibian populations." Thesis, Imperial College London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.478915.
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Berg, Elizabeth A. "The effect of hydrological restoration on nutrient concentrations, macroinvertebrate communities, and amphibian populations in Lake Erie coastal wetlands." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1546553406508401.
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Dimitrie, David. "The effects of two insecticides on California anurans (Rana sierrae and Pseudacris sierra) and the implications for declining amphibian populations." OpenSIUC, 2010. https://opensiuc.lib.siu.edu/theses/368.
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Evidence is growing that agrochemicals are playing a role in the decline of amphibians in California. An area of concern is the Sierra Nevada Mountains, where insecticides used in the Central Valley are aerially transported to amphibian habitats. I examined the effects of two of these insecticides, endosulfan and chlorpyrifos, in two experiments on anuran larvae. For the first experiment I exposed Sierra Mountain yellow-legged frog (Rana sierrae) larvae starting at Gosner stage 25 to each insecticide for 63 d to determine median lethal concentrations (LC50) and sublethal effects on growth and development. In the second experiment Sierran treefrog (Pseudacris regilla) larvae were exposed to chlorpyrifos and endosulfan individually and in combination from Gosner stage 25 through metamorphosis to evaluate the interaction between these insecticides. In the first experiment the endosulfan LC50 was 19.8 µg/L (95% confidence interval, 15.3-52.2 µg/L) and the chlorpyrifos LC50 was 595 µg/L (95% confidence interval could not be determined). Endosulfan concentrations greater than 8 µg/L reduced growth but had no effect on time to metamorphosis. No larvae exposed to chlorpyrifos reached metamorphosis. All larvae exposed to greater than 737 µg/L died before the end of the experiment. Growth was reduced above 325 µg/L and cholinesterase was depressed at 737 µg/L compared to controls. In the second experiment the interactive effects of the insecticides depended on concentration and exposure duration. Chlorpyrifos alone did not affect survival or body size after 30 d, even at concentrations greater than the previously reported LC50. Survival and body size decreased with increasing endosulfan concentrations. In combination, 137 µg/L chlorpyrifos inhibited the negative effects of endosulfan on growth and survival and the positive effects of endosulfan on cholinesterase.
13
Rodrigues, Murilo Guimarães 1978. "Estimating vital rates with imperfect detection in amphibian and reptile populations = Estimando taxas vitais com detecção imperfeita em populações de anfíbios e répteis." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/316218.
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Orientador: Ricardo Jannini SawayaTese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia
Made available in DSpace on 2018-08-23T04:29:37Z (GMT). No. of bitstreams: 1 Rodrigues_MuriloGuimaraes_D.pdf: 4926681 bytes, checksum: 057f2c8aa9c7d1baaa30995a12a9c858 (MD5) Previous issue date: 2013
Resumo: A ecologia de populações investiga os fatores que levam a variação das taxas vitais e, consequentemente, no número de indivíduos. Isso inclui testar hipóteses sobre aspectos da história de vida das espécies e entender os fatores que podem modular a dinâmica populacional. No entanto, a obtenção de dados para testar hipóteses pode ser difícil para populações que apresentam probabilidades de detecção < 1, como anfíbios e répteis. A marcação e recaptura é amplamente usada para estimar a detecção e inferir aspectos de dinâmica populacional e testar hipóteses ecológicas. Neste trabalho empregamos a teoria de marcação e recaptura para testar hipóteses relacionadas à ecologia e conservação de populações de anfíbios e répteis. Utilizamos o programa MARK para implementar modelos de populações abertas e fechadas incorporando a probabilidade de detecção dos indivíduos, para obter estimativas de sobrevivência, e outros parâmetros populacionais usando máxima verossimilhança. Organizamos esta tese em quatro capítulos. Iniciamos enfatizando a importância da probabilidade de detecção, além de simular cenários hipotéticos para demonstrar a relação entre esforço de campo, tamanho ótimo amostral e viés amostral. Em seguida comparamos o efeito de duas técnicas de marcação, o corte de artelhos e o implante de microchips, sobre a sobrevivência individual do sapo ferreiro, Hypsiboas faber. No terceiro capítulo estimamos a sobrevivência e o crescimento populacional da jararaca-ilhoa, Bothrops insularis incorporando emigração temporária aos modelos. Além do estudo de taxas vitais e de dinâmica nas populações, a alocação de energia e suas consequências na sobrevivência individual podem ser testadas com modelos de marcação e recaptura. Assim, no quarto e último capítulo consideramos dois caracteres sexuais presentes no sistema de acasalamento dos lagartos, o tamanho da mandíbula e a coloração chamativa, para comparar as estimativas de sobrevivência entre machos e fêmeas do lagarto cauda de chicote, Cnemidophorus cf. ocellifer. . De forma geral, observamos que a probabilidade de detecção individual nos sistemas estudados foi baixa e condizente com a detecção de vertebrados em ambientes tropicais. Além disso, a inclusão de covariáveis na investigação de parâmetros vitais e no processo de detecção é fundamental para o melhor entendimento dos fatores que explicam a dinâmica de uma população. Especificamente observamos que: (i) demonstramos que as taxas que não incorporam a detecção são enviesadas em relação às estimativas que consideram a detecção, (ii) as estimativas de sobrevivência foram similares em indivíduos de Hypsiboas faber marcados com ablação de artelhos e microchips , (iii) Bothrops insularis apresentou baixa probabilidade de sobrevivência anual e crescimento populacional anual negativo. Por fim, (iv) machos maiores do lagarto Cnemidophorus cf. ocellifer apresentaram sobrevivência mensal menor do que machos menores, mas o oposto foi observado para as fêmeas
Abstract: Population ecology aims to search for factors that lead to variation in vital rates and consequently, in the number of individuals. This includes testing hypotheses about natural history traits and threats to populations. However, obtaining data to test hypotheses is challenging because following individuals in the field can be difficult, especially for amphibians and reptiles, where detection probabilities are often < 1. Mark-recapture methods are widely used to estimate detection probabilities and to test ecological hypothesis. Here we used mark-recapture methods to test hypotheses related to ecology and conservation of amphibian and reptile populations. We implemented open- and closed-population models in Program MARK, to account for detection probabilities and to calculate survival estimates and other population parameters. We organized this dissertation into four chapters. In the first chapter we emphasize the importance of considering detection probabilities besides simulating hypothetical scenarios to show the relationship between field effort, sample size and precision. In the second chapter we used a Cormack-Jolly-Seber model to compare the effect of two amphibian marking techniques, toeclipping and PIT tagging, on survival in the blacksmith tree frog, Hypsiboas faber. In the third chapter our goal was to estimate survival and population growth of the golden lancehead, Bothrops insularis accounting for temporary emigration using Pollock's Robust Design. Besides the study of vital rates and population dynamics, energy allocation and its consequences for survival are testable with mark-recapture models. Thus, in the last chapter we used two traits from the lizard mating system, namely jaw size and courtship coloration, to compare survival estimates between males and females of the whiptail lizard, Cnemidophorus cf. ocellifer. In summary we observed that detection probability on the studied populations were low and similar to other vertebrate populations from the tropics. However, including covariates in estimation models of vital rates and detection is important to obtain more accurate results to explain population dynamics. Specifically we conclude that (i) return rates were biased low in relation to survival estimates that account for detectability, (ii) the estimates of survival were similar between toe-clipped and PIT tagged individuals of Hypsiboas faber, (iii) Bothrops insularis showed low survival probability and negative annual population growth. And (iv) larger Cnemidophorus cf. ocellifer males showed lower monthly survival probability than smaller males but the opposite was found for females
Doutorado
Ecologia
Doutor em Ecologia
14
Pokhrel, Lok Raj. "Mapping the Dorsal Skin Pigmentation Patterns of Two Sympatric Populations of Ambystomatid Salamanders, Ambystoma opacum and A. maculatum from Northeast Tennessee." Digital Commons @ East Tennessee State University, 2009. https://dc.etsu.edu/etd/1784.
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Because of growing concern of habitat fragmentation and its adverse effects on salamander communities in Appalachian region, sympatric populations of ambystomatid salamanders A. opacum and A. maculatum were studied in Northeast Tennessee to address a number of questions: i) the extent of sexual size dimorphism (SSD) in both species, ii) what traits influence the dorsal skin pigmentation and how, iii) whether gender differences in developmental stability occur, and iv) the extent of phenotypic variation within each species. The findings of this study revealed SSD in both species of salamanders. The most parsimonious statistical model was developed that explained the influence of body mass, dorsal body area, and sex on development of dorsal white pigmentation in marbled salamanders. Data on asymmetry indicate that females are under more stress than males in marbled salamanders, while for spotted salamanders nonsignificant asymmetry is indicative of similar level of stress in both sexes. Data on coefficient of variation (CV) suggest stabilizing selection on optimal body size and mass in female marbled salamanders compared to males; however, for spotted salamanders CV indicates relatively similar selection pressure for body size and mass for both sexes.
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Guzy, Jackie. "Maintaining biodiversity with a mosaic of wetlands: factors affecting amphibian species richness among small isolated wetlands in central Florida." Scholar Commons, 2010. https://scholarcommons.usf.edu/etd/1652.
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The biodiversity value of a wetland is linked not only to its position in the landscape relative to other wetlands, but also to its habitat characteristics. I monitored amphibian species richness among 12 small, isolated, and undisturbed wetlands (which occur on lands permitted for phosphate mining) in central Florida during the 2005 and 2006 breeding seasons. I used seven habitat and landscape variables to characterize the environments of the wetlands and generalized linear models to determine which of these variables had the greatest influence on the occurrence of seven amphibian species (Anaxyrus terrestris, Gastrophryne carolinensis, Hyla gratiosa, Lithobates capito, L. catesbeianus, L. grylio, and Pseudacris nigrita verrucosa). Significant models for each species incorporated six of the seven habitat and landscape variables: distance to permanent water (2 spp.), distance to nearest wetland (3 spp.), vegetation heterogeneity (2 spp.), hydroperiod (2 spp.), presence/absence of fish (1 sp.), and distance to canopy cover (1 sp.). I suggest that source/sink metapopulation and patchy population dynamics in a given year are affected in part by environmental variables of ephemeral wetlands as they affect individual amphibian species. I suggest that a diversity of environmental conditions among wetlands produces the greatest amphibian biodiversity in this system, and that conservation and restoration efforts should emphasize environmental heterogeneity.
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Hunter, David, and n/a. "The conservation and demography of the Southern Corroboree Frog (Pseudophryne corroboree)." University of Canberra. Resource, Environmental & Heritage Sciences, 2000. http://erl.canberra.edu.au./public/adt-AUC20060731.143131.
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The documented decline of amphibian populations over the past two decades has increased
attention towards amphibian conservation. Much of this attention has been focused on testing
hypotheses as to the causal factors of these declines, however providing convincing data to
support any of these hypotheses has proved difficult. The testing of these hypotheses and the
implementation of endangered species recovery programs has been restricted by a lack of
knowledge of the ecology and population demography of amphibian species that have
suffered dramatic declines.
This thesis presents aspects of the research phase of the recovery program for the Southern
Corroboree Frog, Pseudophryne corroboree, a species that declined to very low numbers
during the early 1980's. In particular, this research aimed to determine the distribution,
abundance, population dynamics and demography of this rare species. A complete
reassessment of the conservation status of P. corroboree was undertaken and the nature of the
persistence of this species across the landscape was analysed. Temporal trends in abundance
and its relationship with population size were also investigated. Early life-history
survivorship and recruitment to metamorphosis were studied at the scale of individual nest
sites and populations, and the adult male population age structure and annual mortality were
investigated using skeletochronology.
The shout/response survey technique was used to survey and monitor the number of breeding
male P. corroboree during this study. This method was found to provide consistent results
when the surveys were conducted over a short (two week) period during the peak breeding
season in January. Neither time of day, nor the number of males present at a pool, was found
to influence the level of responsiveness of male P. corroboree to the shout/response
technique. Variation in the number of responding males to the shout/response technique
through the breeding season, assessed at a single site over two seasons, was unimodal with the
peak responding period occurring during the last two weeks of January during both the 1998
and the 1999 breeding seasons.
A systematic survey covering 213 sites across the entire historic distribution of P. corroboree
found this species to be persisting at 79 sites. The majority of these sites were in the northwestern
portion of the species former range, around the Jagungal Wilderness area, while no
extant sites were found in the south-eastern portion of the species former range in the Smiggin
Holes and Perisher Blue ski resorts area. The overall abundance of males at persistent sites
was extremely low, with 92 percent of sites having fewer than ten responding males. Only
one site was found to support greater than fifty responding males. A logistic regression
analysis found the persistence of P. corroboree to be associated with increased number of
pools within a site, decreased distance to nearest extant population and geographic position
(latitude and longitude) in the landscape. While annual variation was observed in the number
of breeding males for individual sites, there was no overall trend for an increase or decrease in
the number of males, regardless of population size. The average annual extinction rate for
local populations was five percent during this study, with those populations becoming extinct
having very few breeding males (between one and three) during the previous season.
Embryonic and tadpole survivorship was monitored for individual nests at three sites across
three years. Recruitment to metamorphosis for P. corroboree was characterised by high
variation in survivorship between nest sites, populations and years, while overall recruitment
for nest sites was skewed towards lower survivorship. Average nest survivorship to
metamorphosis across all sites and years was ten percent but the skewed nature of this
survivorship meant that the majority of nest sites attained very low or no survivorship. The
low proportion of nest sites that did attain high survivorship provided the greatest contribution
to overall recruitment. The levels of embryonic and tadpole mortality observed in this study
would be providing a considerable contribution to the regulation of current population sizes.
The greatest level of early life-history mortality was observed during the late autumn/winter
egg and tadpole stage, with high survivorship during the summer and early autumn egg stage
and the post-winter tadpole stage. The estimated sex ratio for seven populations, based on the
number of eggs within male nest sites, indicated that for most populations, regardless of
population size, there was a greater proportion of females to males. In general, the estimated
sex ratio of smaller populations showed greater annual variation and had a lower average
number of females to males than the single large population.
Tadpole surveys conducted across remnant populations during both 1998 and 1999 found
recruitment to metamorphosis to be very low for the majority of populations. A third of all
populations during both years attained no recruitment to metamorphosis, with those
populations that did attain recruitment typically having fewer than 20 tadpoles. While sites
with more frogs generally recruited more tadpoles, there was no strong relationship between
population size and the number of tadpoles recruited per male at the scale of either pool or
site. There was also no significant difference in recruitment levels between the two years.
Tadpole surveys across breeding pools within the single large population also found very low
tadpole abundance. There was no strong relationship between the number of male frogs at a
pool and the number of tadpoles per male and there was no significant difference in tadpole
abundance between the two years. Based on the low density of males at pools and sites
(typically less than five), and the skewed nature of nest survivorship identified from
monitoring individual nest sites, it seems likely that both deterministic and stochastic factors
are influencing recruitment levels in remnant populations of P. corroboree.
This study determined that adult male P. corroboree could be accurately aged using the
technique of skeletochronology, and this technique was used to determine the adult male
population age structure for three populations. The results indicated that adult male
P. corroboree can reach sexual maturity from metamorphosis in three years, but the majority
of individuals take four years. The oldest individual identified in this study was nine years
old from metamorphosis. The adult male age structure at the single large site showed very
little annual variation, whereas the two smaller populations showed highly pulsed age
structures from one year to the next. The size of adult males was found to be a poor predictor
of age. Annual adult male survivorship, calculated by following cohorts from one year to the
next, was 55 percent. Based on this calculation of annual adult male survivorship, it seems
likely that the initial decline in P. corroboree involved increased levels of adult mortality.
The results of this study indicate that the persistence of. corroboree in the wild is precarious
in the short-term. For this reason, it is recommended that efforts be undertaken to secure this
species ex situ. Attempts to increase population numbers in the wild would greatly benefit
from determining the factor(s) that have caused the decline in this species, however, failure to
do so should not preclude field experimental management aimed at developing technique to
increase the size of remnant populations. This is because it is likely that small population
stochasticity is contributing to the current regulation of population size and it is possible that
the factors that caused the decline in this species cannot be removed from the environment.
17
Smith, M. Alexander. "Spatial ecology of Bufo fowleri." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84844.
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The geographic isolation of populations can result in a metapopulation effect where regional dynamics of extinction and colonization are more important to population viability than local dynamics of individuals' birth or death. When this partial isolation is maintained for many generations genetic variability can be geographically structured. Populations of temperate-zone anuran amphibians are often considered to be geographically isolated on relatively small spatial scales due to the animals presumed high site fidelity and strict dependence on moisture for respiration and breeding. As a result, temperate, pond-breeding anuran amphibian populations are considered likely candidates to test hypotheses of metapopulation theory, movement and phylogeography. Using data from the Fowler's toad, (Bufo fowleri) I test the applicability of metapopulation theory, the likelihood of limited movement and the strength of phylogeographic structure. Specifically, I show that the generalization of the amphibians-as-metapopulations paradigm, due to their limited dispersal capabilities, is not supported (I). Bufo fowleri movement is well described by an inverse power function. Whereas most individuals do not move, some move long distances. There is no sex bias to this movement and I propose the hypothesis that the animals moving the longest distances are aided by the passive action of lake currents (II). B. fowleri juveniles are not a dispersal stage. They move neither farther nor faster than adults. The observation of predominantly juvenile contribution to a dispersal pool is due to their abundance---there are simply many more juveniles than adults (III). My observations of amphibian population turnover do not support the predictions of two specific metapopulation models when parameterized on a local (<10km) or regional scale (~300km) (IV). B. fowleri populations in Canada exhibit both shallow and deep phylogeographic structure. The shallow divisions are geo
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Greenberg, Daniel. "Population dynamics of a declining amphibian." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121577.
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With concern rising over the global decline of amphibian populations, identifying the onset of declines and the factors driving them is paramount. Amphibian populations are naturally characterized by large fluctuations in abundance, which makes separating natural fluctuations from true declines very difficult. By improving our understanding of the natural dynamics of amphibian populations, we can separate normal fluctuations from altered dynamics associated with decline. I apply this principle to an endangered population of Fowler's toads (Anaxyrus [=Bufo] fowleri) in Long Point, Ontario which appears to have gradually declined in abundance. With over two decades of mark-recapture data, I investigate what factors, intrinsic and extrinsic, drive growth in this population. Over this same period, there have been considerable changes to the toads' habitat, as an invasive strain of the common reed, Phragmites australis, has overtaken the wetlands used by toads for breeding. I show that the expansion of this reed has altered the dynamics of the toad population, causing progressive decline due to breeding habitat loss. Prior to 2002, the population of toads was driven by density-dependent growth and overwinter mortality. After 2002, at which point the reeds had eliminated most of the open water habitat, the population of toads responded only to extrinsic factors, particularly the water level of Lake Erie. I then ask whether the expansion of invasive Phragmites has changed not just the quantity of larval habitat, but also its quality, through the release of secondary compounds. I hypothesize that Fowler's toad larvae, as obligate gill breathers, will experience reduced survival, growth, and development in the presence of gill damaging secondary compounds from the invasive Phragmites and native Typha. In contrast, the sympatric Northern leopard frog (Lithobates [=Rana] pipiens) should exhibit similar performance as tadpoles in the presence of secondary compounds, as a facultative gill breather. Contrary to my expectations, I found that Fowler's toad tadpoles had a similar performance across treatments, despite the presence of secondary compounds. Furthermore, the native plant, Typha, but not the invasive Phragmites, appeared to impede growth in Leopard frog tadpoles. Based on these results, I conclude that the expansion of invasive Phragmites has the potential to impact species through changes to available habitat, but not by reducing larval habitat quality. By incorporating population dynamics into the study of amphibian declines we can improve our ability to infer causal links between population declines and the mechanisms that drive them.Alors que le déclin de la population amphibienne mondiale est de plus en plus préoccupant, il est primordial d'identifier les facteurs qui en sont la cause. Puisqu'une certaine fluctuation de population est normale, il est difficile de déterminer si une variation donnée est naturelle ou symptomatique d'un déclin réel. Une meilleure compréhension des fluctuations de la population amphibienne pourrait servir à distinguer entre les facteurs naturels de variation et une altération de dynamique associée à un déclin. Voilà l'idée directrice de cette étude d'une espèce à risque, le crapaud de Fowler (Anaxyrus [=Bufo] fowleri) de Long Point en Ontario, dont la population semble diminuer graduellement. À partir de l'information recueillie sur deux décennies de marquage-recapture, j'ai examiné les facteurs, internes et externes, de variation de leur population. Au cours de la période, leur habitat de reproduction a été considérablement détérioré par la présence d'une espèce envahissante de roseau commun, le Phragmites australis. J'explore le lien entre cette altération de dynamique et le déclin progressif des crapauds de Fowler. Avant 2002, leur population était régulée par des facteurs internes comme la croissance en fonction de la densité et la mortalité hivernale. Depuis, les roseaux communs ont éliminé la plupart de l'habitat en eau libre des crapauds de Fowler, dont la population ne répond plus qu'à des facteurs externes d'influence, en particulier le niveau de l'eau du lac Érié. Ensuite, je cherche à voir si la présence de l'espèce envahissante a influencé, non seulement la quantité d'habitat de reproduction du crapaud de Fowler, mais aussi la qualité de ce qui reste, par la production de composés secondaires. L'hypothèse explorée est que les composés secondaires nuisibles aux branchies, produits autant par l'espèce envahissante Phragmites que par l'espèce native Typha, réduisent les chances de survie, la croissance et le développement des crapauds de Fowler, qui respirent nécessairement par leurs branchies. En toute logique, l'espèce sympatrique grenouille léopard du Nord (Lithobates [=Rana] pipiens), qui respire par ses branchies de façon facultative, devrait être affectée de façon similaire. Cependant, ce n'est pas le cas ; j'ai remarqué que les têtards de crapauds de Fowler n'étaient pas affectés par la présence de composés secondaires. De plus, c'est l'espèce native Typha qui semblait nuire à la croissance des crapauds de Fowler, plutôt que l'espèce envahissante Phragmites. J'en conclus que l'expansion de cette dernière peut influencer plusieurs espèces par une réduction de l'habitat disponible, mais pas par la détérioration de la qualité de son habitat larvaire. En étudiant le déclin amphibien à partir de la dynamique de population, nous pouvons améliorer notre capacité à établir des liens entre le déclin de populations d'espèces et les mécanismes qui y contribuent.
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Bielby, Jon. "Extinction risk and population declines in amphibians." Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/4278.
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This thesis is about understanding the processes that explain the patterns of extinction risk and declines that we see in amphibians, how we can use that understanding to set conservation priorities, and how we can convert those priorities into practical, hands-on research and management. In particular, I focus on the threat posed by the emerging infectious disease, chytridiomycosis, which is caused by the chytrid fungus, Batrachochytrium dendrobatidis (Bd). Amphibians display a non-random pattern of extinction risk, both taxonomically and geographically. In chapter two I investigate the mechanism behind the observed taxonomic selectivity and find that it is due to species biology rather than heterogeneity in either threat intensity or conservation knowledge. In chapter three I determine which biological and environmental traits are important in rendering a species susceptible to declines, focussing on susceptibility to Bd. I found that restricted range, high elevation species with an aquatic life-stage are more likely to have suffered a decline. Using these traits, I predict species and locations that may be susceptible in the future, and which should therefore be a high priority for amphibian research and conservation.
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Regosin, Jonathan V. "Terrestrial habitat use by pool-breeding amphibians in a suburban landscape /." Thesis, Connect to Dissertations & Theses @ Tufts University, 2003.
Find full textAbstract:
Thesis (Ph.D.)--Tufts University, 2003.Adviser: J. Michael Reed. Submitted to the Dept. of Biology. Includes bibliographical references (leaves 124-134). Access restricted to members of the Tufts University community. Also available via the World Wide Web;
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White, Steve. "Population trends, conservation and the trade in amphibians in Asia." Thesis, View the Table of Contents & Abstract, 2005. http://sunzi.lib.hku.hk/hkuto/record/B34737364.
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Middleton, Jessica. "Population ecology of a declining amphibian in relation to density." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114513.
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In species with complex life cycles such as amphibians, population regulation can occur in one or multiple stages. Density effects in the larval, aquatic stage of the amphibian life cycle have been widely documented, leading many researchers to assume that this is the stage in which amphibian populations are regulated. However, recent evidence suggests that factors affecting survival and reproduction in the terrestrial stage may play a greater role in the growth and decline of amphibian populations than previously thought. I review the evidence for density-dependent population regulation in the terrestrial stage of amphibians and argue that variation in body size may be an important mechanism linking population density to changes in population growth rate (CHAPTER ONE). I used data from a 23-year population survey at Long Point, Ontario and conducted summer growth-rate surveys to examine the body size-abundance relationship in Fowler's Toad (Anaxyrus fowleri). Over the past 10 years of the population survey at Long Point, we observed a significant increase in body size (R² = 0.874, p = <0.001) that was coincident with a previously detected negative trend in abundance. The age structure of this population is highly unstable, but overall the average age is getting older (R² = 0.325, p= < 0.01) (CHAPTER TWO). Somatic growth rates in Fowler's toad toadlets are also highly variable and are significantly inversely correlated with the density of adults (R² = 0.98, p = 0.010) (CHAPTER THREE). The single most important factor influencing average body size on a long time-scale is abundance (R² = 0.713, p = <0.001) (CHAPTER FOUR). Therefore, body size variation in these toads is likely related to density-dependent resource availability for growth in the terrestrial stage.Pour des espèces ayant des cycles de vie complexes tels les amphibiens, la régulation de leur population peut se produire dans un ou plusieurs stades. Les effets de la densité au stage larvaire aquatique du cycle de vie de l'amphibien ont été largement documentés amenant plusieurs chercheurs à assumer que c'est à ce stage que la régulation de leur population se produit. Toutefois, des preuves récentes suggèrent que des facteurs affectant la survie et la reproduction au stage terrestre peuvent jouer un plus grand rôle dans la croissance et le déclin de la population des amphibiens contrairement à ce que l'on pensait auparavant. Je fais la revue de la preuve de la régulation de la population qui dépend de la densité au stage terrestre des amphibiens et j'argumente que la variation de la masse corporelle pourrait être un mécanisme important reliant la densité de la population aux changements du taux de croissance de la population (CHAPITRE UN). J'ai utilisé les données d'un relevé de la population sur une période de 23 ans à Long Point, Ontario et mené des relevés du taux de croissance durant l'été afin d'examiner la relation entre la dimension et la masse corporelle du crapaud de Fowler (Anaxyrus fowleri). Durant les 10 dernières années du relevé de la population à Long Point, nous avons remarqué une augmentation significative de la masse corporelle (R² = 0.874, p = <0.001) qui coïncidait avec une tendance négative de leur abondance détectée précédemment. La structure de l'âge de cette population est très instable, mais dans l'ensemble la moyenne d'âge est plus vieille (R² = 0.325, p= < 0.01) (CHAPITRE DEUX). Les taux de croissance somatiques des petits du crapaud de Fowler sont hautement variables et inversement corrélatifs à la densité des adultes (R² = 0.98, p = 0.010) (CHAPITRE TROIS). Le seul facteur d'importance qui influence la dimension corporelle moyenne sur une longue période c'est l'abondance (R² = 0.713, p = <0.001) (CHAPITRE QUATRE). Ainsi, la variation de la dimension corporelle de ces crapauds est vraisemblablement reliée à la croissance somatique laquelle dépend de la densité au stage terrestre.
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Hime, Paul Michael. "GENOMIC PERSPECTIVES ON AMPHIBIAN EVOLUTION ACROSS MULTIPLE PHYLOGENETIC SCALES." UKnowledge, 2017. http://uknowledge.uky.edu/biology_etds/45.
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Genomes provide windows into the evolutionary histories of species. The recent accessibility of genome-scale data in non-model organisms and the proliferation of powerful statistical models are now providing unprecedented opportunities to uncover evolutionary relationships and to test hypotheses about the processes that generate and maintain biodiversity. This dissertation work reveals shallow-scale species boundaries and population genetic structure in two imperiled groups of salamanders and demonstrates that the number and information content of genomic regions used in species delimitation exert strong effects on the resulting inferences. Genome scans are employed to test hypotheses about the mechanisms of genetic sex determination in cryptobranchid salamanders, suggesting a conserved system of female heterogamety in this group. At much deeper scales, phylogenetic analyses of hundreds of protein-coding genes across all major amphibian lineages are employed to reveal the backbone topology and evolutionary timescales of the amphibian tree of life, suggesting a new set of hypotheses for relationships among extant amphibians. Yet, genomic data on their own are no panacea for the thorniest questions in evolutionary biology, and this work also demonstrates the power of a model testing framework to dissect support for different phylogenetic and population genetic hypotheses across different regions of the genome.
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Homan, Rebecca Newcomb. "Conservation studies of amphibian health at individual, population and landscape scales /." Thesis, Connect to Dissertations & Theses @ Tufts University, 2003.
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Thesis (Ph.D.)--Tufts University, 2003.Director: J. Michael Reed. Submitted to the Dept. of Biology. Includes bibliographical references (leaves 97-114). Access restricted to members of the Tufts University community. Also available via the World Wide Web;
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Nunziata, Schyler O. "USING GENOMICS TO UNDERSTAND POPULATION DEMOGRAPHICS IN THE CONTEXT OF AMPHIBIAN CONSERVATION." UKnowledge, 2017. http://uknowledge.uky.edu/biology_etds/49.
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Understanding the demography of species over recent history (e.g., < 100 years) is critical in studies of ecology and evolution, but records of population history are rarely available. Large single nucleotide polymorphism datasets generated with restriction-site associated DNA sequencing (RADseq), in combination with demographic inference methods, are improving our ability to gain insights into the population history of both model and non-model species. However, to assess the performance of genetic methods it is important to compare their estimates of population history to known demography, in both simulation and empirical settings. Here, I used a simulation approach to examine the potential for RADseq datasets to accurately estimate effective population size (Ne) in Wright-Fisher populations over the course of stable and declining population trends, and distinguish stable from steadily declining populations over a contemporary time scale (20 generations). Overall, my results reveal that demographic inference using genome-wide data can be successfully applied to estimate Ne, and the detection of population-size declines. Next, I assess these methods in an empirical study from a wetland with 37 years of amphibian mark-recapture data to study the utility of genetically-based demographic inference on salamander species with documented population declines (Ambystoma talpoideum) and expansions (A. opacum). For both species, demographic model inference supported population size changes that corroborated mark-recapture data. To further validate these findings, I used individual-based population models of the pond-breeding salamander, Ambystoma opacum, with life-history parameters estimated from a long-term dataset, over a 50 year projection. My results demonstrate that genetically estimated Ne is positively correlated with census size in isolated and subdivided A. opacum populations. Finally, I investigated metapopulation patterns of genomic diversity in A. opacum and A. talpoideum and how migration may impact Ne estimation. I found strong patterns of subpopulation structuring, signatures of migration between subpopulations, and differences in Ne at the subpopulation level in both species. Overall, my findings suggest the ability of genomic data to reconstruct recent demographic changes, which can have important applications to conservation biology, and ultimately can help us elucidate the effects of environmental disturbances in the demography of endangered or declining species.
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Miaud, Claude. "La dynamique des populations subdivisées : étude comparative chez trois amphibiens urodèles (Triturus alpestris, T. helveticus et T. cristatus)." Lyon 1, 1990. http://www.theses.fr/1990LYO10029.
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La dynamique des populations des trois especes est abordee dans une station comportant quatre mares proches. Trois annees de capture et marquage revelent que 80% des adultes sont fideles a leur mare, ce qui implique une organisation en sous-populations. Les caracteristiques demographiques (effectifs, age par squelettochronologie, fecondite, survie des ufs et des larves) permettent de proposer un nouveau modele de dynamique des populations de triturus. La description des caracteristiques des quatre mares montrent l'importance de la presence de vegetation sur la production de jeunes. Fidelite des adultes et opposition entre sites productifs et improductifs sont a la base de l'organisation en metapopulation. La selectivite des supports de ponte est etudiee dans les mares et en conditions de laboratoire. Les femelles pondent de preference pres de la surface et sur des vegetaux differents entre les trois especes. L'ensemble des resultats est discute dans le cadre des strategies demographiques et du probleme du morcellement des populations. Une revue bibliographique des modalites de la reproduction des urodeles est proposee dans la conclusion
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Becker, Sarah Nthabiseng. "Hanging out with the cool frogs : do operative and body temperatures explain population response to disease? /." Available to subscribers only, 2009. http://proquest.umi.com/pqdweb?did=1885431351&sid=4&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Greenwald, Katherine Rose. "Habitat fragmentation, functional landscape connectivity, and metapopulation processes in amphibians." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243366608.
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Paloski, Rori A. "Relationship between lakeshore development and anuran populations in Portage County, Wisconsin /." Link to full-text, 2006. http://epapers.uwsp.edu/thesis/2006/paloski.pdf.
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Perret, Nadège. "Dynamique de population en habitat fragmenté chez deux espèces d'amphibiens urodèles (Triturus alpestris et T cristatus)." Lyon 1, 2000. http://www.theses.fr/2000LYO10283.
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La dispersion est un processus clé en écologie en raison de ses implications multiples tant au niveau de la dynamique des populations fragmentées, des variations des stratégies d'occupations de l'espace que de la viabilité des populations. Nous avons cherché dans ce travail à mettre en évidence les modalités de dispersion chez deux espèces d'amphibiens urogèles : les tritons alpestres et les tritons crêtés (espèce patrimoniale). Ces deux espèces, par leur mode de reproduction qui généère une agrégation des adultes dans des mares, représentent typiquement le schéma structurel d'espèces se reproduisant dans des patches d'habitats framgentés (les mares). L'habitat est caractérisé par une hétérogénéité spatio-temporelle de la capacité d'accueil qui est à l'origine de processus de dispersion. Les méthodes utilisées pour appréhender les processus dispersifs seront tour à tour l'analyse démographique par capture-marquage-recapture (CMR) dans différentes populations framgentées, la modélisation mathématique et l'expérimentation. Nous avons tout d'abord caractérisé l'impact des méthodes de marquage (tatouage et transpondeur) sur la survie des tritons alpestres. [. . . ] Les mécanismes comportementaux qui influencent la sélection de l'habitat lors de la dispersion sont étudiés. [. . . ] L'ensemble de ces résultats sont ensuite discutés en regard avec les théories actuelles concernant l'évolution de la dispersion, la variabilité spatio-temporelle de la distribution des individus dans les populations fragmentées liées à la dispersion, et enfin, en rapport avec la sélection de l'habitat par le comportement d'attraction par les congénères comme vecteur d'agrégation lors de la reproduction de ces amphibiens
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Bridges, Christine M. "The effects of a chemical stressor on amphibian larvae : individual, population, and species level responses /." free to MU campus, to others for purchase, 1999. http://wwwlib.umi.com/cr/mo/fullcit?p9946247.
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Greenwald, Katherine R. "Habitat fragmentation, functional landscape connectivity, and metapopulation processes in amphibians." Columbus, Ohio : Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1243366608.
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Bakkegard, Kristin Ann. "The Genetics of Colonization in Two Amphibian Species After the 1980 Eruption of Mount St. Helens." DigitalCommons@USU, 2008. https://digitalcommons.usu.edu/etd/77.
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The genetics of colonization is understudied in salamanders but has large conservation implications as new habitats are formed or restored to their previous condition. The 1980 eruption of Mount St. Helens provided a natural experiment to study the genetic effects of a large infrequent environmental disturbance on two species of salamander, Taricha granulosa (Rough-skinned newt) and Ambystoma gracile (Northwestern salamander). Both these species breed in ponds, and are thought to exhibit high breeding site fidelity and low vagility. I designated three treatments based on the effects of the eruption: new ponds (created by the eruption, immigrants only), recovery lakes (in blast zone, survivors plus immigrants), and reference lakes (unaffected by eruption, assumed to represent pre-eruption genetic diversity measures). Salamanders took at least nine years to colonize the new ponds. I studied the population genetics of colonization and recovery using microsatellites and AFLPs (amplified fragment length polymorphisms) to measure genetic diversity, gene flow, and population substructure at Mount St. Helens National Volcanic Monument. Based on population genetics theory and the life history characteristics of these pond-breeding amphibians, I predicted that genetic diversity would be lower in newly colonized ponds compared to recovery or reference sites. I also expected significant levels of population substructuring. Finally, I predicted that because of their lower vagility and large number of neotenes, that A. gracile would have less gene flow and a greater degree of population substructuring than T. granulosa. My predictions were not supported by my data. There was no loss of genetic diversity in new or recovery populations in either species. There was no strong evidence for population substructure by either AMOVA, isolation by distance or principal components analysis. Gene flow (Fst) was high in both species. Taricha granulosa and A. gracile were found to be resistant to a large infrequent environmental disturbance. Loss of genetic variability in new populations cannot automatically be assumed. Predicting dispersal and colonization ability based on the broad category of pond-breeding amphibian is not always reliable.
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Charbonnier, Julie. "Persistence of the Larval Environment on Post-Metamorphic Performance and Population Dynamics in Amphibians." VCU Scholars Compass, 2017. http://scholarscompass.vcu.edu/etd/5019.
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Organisms with complex life cycles may experience diverse stressors during their development. Stressors experienced in early life stages may influence the quantity and quality of individuals in later life stages. However, it is unclear if these effects persist later in life and how they may influence population dynamics. This dissertation uses two amphibian species, the Western spadefoot toad (Pelobates cultripes) and the spotted salamander (Ambystoma maculatum) to explore how biotic and abiotic factors experienced in aquatic and terrestrial environments influence phenotype and survival. We use a combination of field mesoscosm studies, laboratory studies and modeling to explore how early life history stressors persist in diverse environmental contexts. In Chapter 1, pond drying and larval density negatively influence multiple aspects of phenotype in the Western spadefoot toad. In Chapter 2, reduced body size due to larval stressors persisted in the first year of life in spotted salamanders in both high and low terrestrial resource environments. Additionally, there was no relationship between size at metamorphosis and post-metamorphic terrestrial survival. In Chapter 3, low terrestrial moisture levels reduced post-metamorphic growth rates by reducing food intake in juvenile spotted salamanders from both high and low larval density treatments. In Chapter 4, we scale up the effects of reduced body size in the Western spadefoot toad to explore how reduced body size due to pond drying may influence population densities using a stage specific matrix model. Reduced body size, by delaying maturity, may reduce adult densities in the Western spadefoot toad. This dissertation suggests that life stages are highly interconnected, as stressors experienced early in life stage may persist through their effects on phenotype in the absence of compensatory mechanisms. Variation in later life stages may also influence phenotype, but may not completely erase effects of early environments. Stressors experienced early in life may also translate to population level consequences, especially when organisms experience multiple stressors across life stages.
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Harper, Elizabeth B. "The role of terrrestrial habitat in the population dynamics and conservation of pond-breeding amphibians." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/4693.
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Thesis (Ph. D.)--University of Missouri-Columbia, 2007.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on September 25, 2007) Vita. Includes bibliographical references.
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Kilburn, Vanessa. "Persistence and prevalence of the enzootic chytrid fungus, «Batrachochytrium dendrobatidis», in relation to amphibian population decline in Panama." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=32555.
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The pathogenic chytrid fungus, Batrachochytrium dendrobatidis, causes population decline and extinction of numerous species of tropical, principally montane, amphibians. Is B. dendrobatidis an enzootic pathogen emerging as a disease, or rather a novel invasive pathogen infecting naïve amphibians? Are only high-elevation amphibians susceptible to the pathogen? If the chytrid is enzootic, then it may be in the environment before or after epidemic decline and may infect both montane and lowland amphibians as well as other organisms. To determine distribution of the pathogen and corresponding anuran abundance, I established eight research sites of varying elevations and stages of epidemic infection from west to east, ranging from 45 m to 1215 m elevation throughout Panama west of the Canal. Differential infection susceptibility among anurans was addressed in relation to three ecological factors: anuran body size, season and habitat. Prevalence and infection intensity of the chytrid were determined at all sites and for all factors using sensitive DNA-based RT-qPCR amplification. Amphibian populations at all elevations and stages of decline showed at least some degree of chytrid infection, and the chytrid was found on reptiles. In addition to presence of the pathogen, effects of the disease chytridiomycosis were variably seen at all elevations. Habitat and season did not seem to have a strong effect on infection prevalence and/or intensity, but frogs did appear to show greater infection at smaller anuran body sizes. All of the above results are suggestive of an enzootic pathogen and perhaps only the current epidemic of chytridiomycosis disease is novel. Since the infectionLe champignon pathogène chytrid, Batrachochytrium dendrobatidis, cause la diminution et l'extinction de nombreuses populations d'amphibiens tropicaux, principalement dans les regions à haute altitude. Si le champignon est endémique, il peut rester dans l'environnement après le passage d'une épidémie, contaminant les amphibiens des hautes et basses terres, ainsi que les autres organismes. Les sites de recherche étaient établis à diverses élévations et à différents stades de l'épidémie, à l'ouest du canal de Panama, où l'état des populations d'amphibiens pouvait être examiné. L'hypersensibilité différentielle des grenouilles à la maladie était adressée pour trois facteurs: la taille des grenouilles, la saison et l'habitat. La prévalence et l'intensité de l'infection étaient déterminées pour chaque facteur à tous les sites en utilisant la technique du RT-qPCR. Les amphibiens de toutes les élévations et de tous les stades de l'épidémie ont montré au moins un niveau d'infection, indiquant la présence d'un pathogène endémique. Le chytrid a aussi été trouvé sur les reptiles. En plus de la présense du champignon, les symptômes de la maladie chytridiomycosis ont même été remarqués sur les grenouilles des terres basses. La prévalence de l'infection est restée similaire pour les forêts et les ruisseaux, et aussi pour les deux saisons, et plus élevée pour les petites grenouilles que pour les plus grosses. Puisque l'infection peut rester dans les communautés amphibiennes à toutes altitudes, habitats et saisons, qu'elle peut persister pour longtemps (jusqu'à 11 ans), et qu'elle peut survivre sur d'autres organismes, la réintro
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Miller, Courtney A. "Understanding the impacts of current and future environmental variation on central African amphibian biodiversity." ScholarWorks@UNO, 2018. https://scholarworks.uno.edu/td/2542.
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Global climate change is projected to impact multiple levels of biodiversity by imposing strong selection pressures on existing populations, triggering shifts in species distributions, and reorganizing entire communities. The Lower Guineo-Congolian region in central Africa, a reservoir for amphibian diversity, is predicted to be severely affected by future climate change through rising temperatures and greater variability in rainfall. Geospatial modelling can be used to assess how environmental variation shapes patterns of biological variation – from the genomic to the community level – and use these associations to predict patterns of biological change across space and time. The overall goal of this dissertation is to examine potential impacts of climate change on amphibian diversity in central Africa. Geospatial modeling is used to: 1) map the distribution of the amphibian fungal pathogen, Batrachochytrium dendrobatidis (Bd) in a biodiversity hotspot in Cameroon under current and future climate; 2) assess phenotypic and adaptive genomic variation in a widespread frog species, Phrynobatrachus auritus, in order to predict areas where populations may best adapt under climate change; 3) determine how amphibian community composition may shift with climate change and which areas may experience greatest loss of functional groups. Findings show that most Bd samples belong to a globally hypervirulent lineage. However, areas of highest predicted environmental suitability for Bd are predicted to shrink under warming temperatures. Within P. auritus, most phenotypic and genomic turnover occurred across known ecological gradients and are heavily influenced by seasonal precipitation. Current amphibian beta diversity is greatest throughout the Cameroonian highlands and forest-savanna ecotones flanking the central Congolian lowland forests. Greatest shifts in community composition under climate change are predicted to occur in coastal Cameroon and its eastern border whereas the greatest predicted loss of functional richness was in central Gabon. Overall, this dissertation shows that areas of elevated environmentally-associated phenotypic, genomic, and community turnover are associated with key ecological gradients. Regions predicted to experience high genomic mismatch, large shifts in community composition, and high loss of functional richness resulting from climate change may warrant conservation attention.
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Pituello, Fabienne. "Premiers evenements de la neurogenese chez un vertebre (amphibien) : emergence precoce de sous-populations neuronales in vitro." Toulouse 3, 1989. http://www.theses.fr/1989TOU30140.
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Certaines cellules du neurectoderme isolees immediatement apres l'induction neurogene du microenvironnement embryonnaire et cultivees in vitro dans un milieu defini, sont capables de se differencier en neurones typiques, exprimant des molecules marqueurs specifiques. Cette differenciation morphologique s'accompagne de l'expression de neurotransmetteurs tels l'acetylcholine et les catecholamines. Au cours de ce travail de these, l'auteur a mis en evidence dans ces memes cultures, l'expression initiale du gaba (acide gamma-aminobutyrique) et de son enzyme de biosynthese, la gad (decarboxylase de l'acide glutamique) ainsi que l'expression de divers neuropeptides: somatostatine, enkephalines et substance p. L'ensemble des proprietes neuronales: biosynthese, relargage, capture et degradation de neurotransmetteurs, sont acquises. L'auteur a egalement montre qu'il n'y a pas co-expression dans un meme neurone de deux neuromediateurs. Ces donnees demontrent clairement que 1) certaines neuroblastes ont acquis, des l'induction neurogene, la capacite d'exprimer des molecules neuroactives, 2) que des induction neurogene, des sous-populations neuronales distinctes emergent a partir du neurectoderme isole en culture. L'etude de l'origine embryonnaire de ces sous-populations neuronales, necessite l'obtention d'un marqueur precoce de determination neurale. La proteine go exprimee par certaines cellules du neurectoderme avant que tout premier signe de differenciation n'apparaisse, pourrait constituer un tel marqueur
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Williams, Lori Ann. "Amphibian Population and Community Characteristics, Habitat Relationships, and First-Year Responses to Clearcutting in a Central Appalachian Industrial Forest." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/10129.
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The overall goal of this project was to provide baseline data on amphibian species richness, relative abundance, and habitat use for a long-term landscape ecology study on MeadWestvaco industrial forest in the Allegheny Highlands of West Virginia. From results of area-constrained daytime searches (10 m x 10 m plots) across the landscape, I developed 9 regression models to predict amphibian relative abundance. I constructed models for each year for all plots on all habitat types, plots that were in a Stream Management Zone (SMZ), and plots that were in upland, or non-SMZ, habitat. Distance to perennial or ephemeral streams or perennial ponds (SMZ classification), the amount of available rocks along transects, and site index were the 3 most important habitat variables in models for all plots combined and were responsible for 24-32% of the inherent variation in population relative abundance. Other habitat variables that were significant in models were year, % canopy cover, the amount of available woody debris of decomposition classes 3-5 along transects, % woody stems (<7.5 cm DBH), soil pH, and % herbaceous vegetation. R2PRESS values for all 9 models ranged from 0.08 to 0.35. Amphibian relative abundance showed positive relationships with all significant habitat variables with the exception of year and % woody stems.
In natural cover object use/availability analyses, I discovered salamanders preferred rocks over woody debris, relative to the amount available of each. Salamanders preferred flat rocks to any other shape, flagstones to any other type of rock, and rock lengths in the 31-40 cm class. Preferred wood widths were in class 5-10 cm, while preferred wood lengths were in class <50 cm; salamanders exhibited strong preferences for wood in higher states of decomposition (class 3-5).
I provided baseline, preharvest data for 28-acre reference areas on 9 forest compartments scheduled for clearcuts. I sampled all 9 reference areas preharvest and sampled 3 during year 1 postharvest using coverboard and night plot surveys. On these 3 areas, species richness declined from preharvest to postharvest, but species diversity showed little change. Overall relative abundance declined significantly preharvest to postharvest with coverboard sampling (p=0.0172) and night plot sampling (p=0.0113). At coverboard stations, relative abundance declined significantly from preharvest to postharvest at a distance of 5-10 m (p=0.0163) and 40-50 m (p=0.0193) away from adjacent mature forest.
Finally, using Pianka's index, I compared the night plot and coverboard sampling techniques in terms of proportions of the 4 most common species captured. These sampling techniques on average were >80% similar for all reference areas.Master of Science
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Sung, Yik-hei, and 宋亦希. "Impacts of illegal trapping and plantation forestry on herpetofaunal populations." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B48199308.
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Globally, as many as 30% of amphibians and 23% of reptile species are threatened and require urgent conservation action. The major threats are primarily caused by anthropogenic activities. This research aimed to investigate the impacts of two anthropogenic threats, over-exploitation and habitat changes on herpetofaunal populations in Hong Kong.
Platysternon megacephalum has been heavily depleted because of severe hunting pressure for the food and pet trades. Low densities of individuals and few remaining intact populations have limited our ability to study their ecology. I conducted mark-recapture and radio-telemetry studies on P.megacephalum populations in five streams in Hong Kong, one of which was free from trapping, over 34 months (2009–2011) to investigate the impacts of illegal trapping on populations of P.megacephalum and their spatial ecology and growth. Illegal trapping was associated with the absence of large adults, smaller body sizes of adults and skewed ratios of juveniles to adults. Home ranges were relatively small with a mean 100% minimum convex polygon 996m2. Males moved longer distances than females and both sexes moved longer distances in wet seasons. P.megacephalum was highly aquatic, preferring to stay in pools, and their microhabitat preferences were affected by stream width and depth, and substrate types. Juvenile P.megacephalum grew rapidly, with growth declining after attainment of sexual maturity. The average ages of sexual maturation were eight years for females. Illegal trapping remains the major threat to P.megacephalum populations and I recommend that regulatory personnel identify key streams and patrol regularly against illegal trapping to safeguard remaining populations.
In Hong Kong, large areas of primary forest have been replaced by secondary forests and plantations, and changes in tree species composition have often led to alteration of associated plant and animal communities. I examined the herpetofaunal assemblages in secondary forests and exotic Lophostemon confertus plantations. Amphibian abundances were higher in secondary forests while reptile abundance, species richness of amphibian and reptiles were similar. Secondary forests provided better habitats for amphibians and I recommend the planting of a mixture of native tree species and the thinning of exotic trees in future plantation management efforts in South China.
Our knowledge about the effectiveness of different herpetofaunal survey methods in Southeast Asia is limited. To fill the information gap, I examined the effectiveness of three survey methods, including transect surveys, pitfall traps and coverboards, for sampling terrestrial herpetofauna. Transect surveys were most effective at sampling species richness and pitfall traps were most efficient in capturing high numbers of reptiles. The results of this study will aid researchers in assessing the feasibility of and choosing herpetofaunal survey methods in Southeast Asia.
Despite the severe threats that herpetofauna are facing, our understanding of their ecology and conservation needs remains limited. More research and the initiation of monitoring programs for herpetofauna, strengthened enforcement of existing regulations, and proper habitat management are crucial for the conservation of herpetofauna in South China.published_or_final_version
Biological Sciences
Doctoral
Doctor of Philosophy
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Clarke, Charlotte Louise. "Investigating the host-parasite dynamics of a novel amphibian dermocystid disease in an isolated population of palmate newts in the UK." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/28815.
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Emerging infectious diseases (EIDs) have been identified as a key factor in significant amphibian mortalities and global declines. Disease has been largely attributed to just two pathogens, Batrachochytrium dendrobatidis (Chytrid) and Ranavirus, however, an increasing number of amphibian disease cases across Europe are being attributed to a group of unusual fungal-like pathogens of the order Dermocystida. Despite representing an old lineage of amphibian pathogens first described in 1903, very little is known about amphibian- Dermocystids. In 2006, diseased palmate newts on the Isle of Rum, Scotland were reported. Clinical signs appeared consistent with heavy infestations of Dermocystid disease, however oedematous pathologies not previously described in the literature were also observed, suggesting a severe case of disease. This thesis develops the first comprehensive pathogen profile of a novel amphibian-infecting Dermocystid causing severe disease in an isolated population of palmate newts (Lissotriton helveticus) on the Isle of Rum, Scotland. Molecular phylogenetics and histopathology techniques were used to characterise the pathogen, confirming its affiliation to the Dermocystids and identifying it as the second formally described species in the genus Amphibiothecum (meredithae). By incorporating histopathology, field observations and study trials a broader understanding of disease dynamics was achieved. Pathogen cyst developmental stages were assigned to distinct gross pathologies, determining a putative disease cycle. In addition, a large disparity in disease outcome was evident, with cases suggesting involvement of innate immune systems with apparent host recovery, alongside cases with severe morbidity and mortality. Following the development of a pathogen profile, the spatio-temporal dynamics of disease were explored across three consecutive years, from 2014 to 2016. The temporal patterns observed within a single season were first examined across a small sub-set of sites, highlighting a degree of stability in disease prevalence and environmental variables. This within-season survey also provided a temporal dataset of disease presentation, allowing for disease progression to be assessed at the population level, investigating the impact of time on disease presentation and morbidity. For example, an overall linear trend in disease progression was observed where the burden of discrete cysts, thought to represent an initial stage of infection was highest at the beginning of the season, appearing to be ‘replaced’ by larger lesions representing later stage pathologies. Finally, ulcerations that facilitate the release of mature pathogen spores (or sporangia) occurred in the highest abundance towards the end of the season. However the prevalence of the most severe oedematous stages did not always fit with this linear progression of disease and may be driven by other factors. Understanding the within-season dynamics, and confirming a temporal stability in disease prevalence, allowed for broader spatial analysis to be performed without the need to account for samples taken at different points in time. Data collected from a broad spatial survey conducted in 2014 was explored to determine the spatial distribution of infection on Rum, and to investigate the relationships between the incidence, prevalence and severity of disease to environmental conditions and host population structure (e.g. sex ratios). Disease was widespread but heterogeneously distributed across Rum, with site-to-site variation in the incidence and prevalence linked to water pH where low pH environments were associated with low disease prevalence. An apparent sex-linked bias in disease was determined where males were more susceptible, but this does not appear to impact the host population structure of infected sites. The observed relationships between disease prevalence and environmental conditions were further utilised to test the use of disease prediction maps as a means to estimate disease across unsampled locations on the Island. Spatial surveys were subsequently conducted in 2015 and 2016, providing annual data on the distribution and prevalence of disease. Interannual variation at the site level was used to explore key factors influencing the stability of disease, identifying an association between changes in host population structure and increasing disease levels. Spatio-temporal fluctuations at the island level alluded to the overall state of disease on the island and changes to disease risk overtime. Whilst spatial clusters of changing disease prevalence were identified, which could indicate unusual patterns of epidemic spread, these conclusions would be speculative and as no consistent, significant increase in disease was determined or expansion in range, disease likely represents an endemic infection dictated heavily by etiological factors. In order to facilitate future studies and nation-wide surveys such as those conducted for Chytridiomycosis and Ranavirosis, this thesis concludes by trialling non-invasive diagnostic techniques. Environmental DNA and dermal swabbing provides the basis for the development of alternative sampling protocols to improve large-scale survey potential, and lead to a deeper understanding of these pathogens. This study represents the first formally described case of Dermocystid in the UK as well as providing the first detailed spatio-temporal study of an amphibian- Dermocystid. Identifying significant predictors of disease alongside disease prediction maps and potential methods for quick disease diagnosis, provides the tools for future, large-scale analyses to understand the distribution of disease across mainland UK, host range and the risk to native amphibian species.
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Bell, Kristen E. "Conservation ecology of amphibians and reptiles in Sarapiqui, Costa Rica : forest fragmentation and long term population change." FIU Digital Commons, 2005. http://digitalcommons.fiu.edu/etd/1481.
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In order to explore the conservation ecology of frogs and lizards in the Sarapiqui region of Costa Rica, I compared populations and communities among forest fragments and La Selva Biological Station, as well as across 35 years of sampling at La Selva. Species richness in nine fragments combined was 85% of that found in La Selva, and community composition varied among sites and by fragment size class. Although communities in fragments differed fundamentally from those in intact forest, the high diversity observed across all fragments indicates that preserving a network of small forest patches may be of great conservation value to the herpetofauna of this region. According to data from past studies at La Selva, most common species of leaf-litter frogs and lizards demonstrated significant decreases in density over the 35-year period. My findings may represent either natural population fluctuations or sweeping faunal declines at this site.
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Söderman, Fredrik. "Comparative Population Ecology in Moor Frogs with Particular Reference to Acidity." Doctoral thesis, Uppsala University, Department of Ecology and Evolution, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6828.
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This thesis is an attempt to describe how different environmental factors influence life history traits in different populations, sexes and developmental stages in the moor frog, Rana arvalis. The studied populations are located along 1100 km latitudinal gradient, with pH varying between 4.0 and 8.5. I have used data from both natural populations and common garden experiments.
Reproducing moor frogs were larger and older at high latitudes, indicating a selective advantage of large size at high latitudes and/or earlier reproduction at low latitudes. When controlling for age I found that frogs were older and smaller at low pH, which may be a result of a reduced growth rate due to acid stress. The both sexes respond differently to different environments, with the lowest sexual dimorphism in body size found in the acid environments. This is possibly caused by a trade-off between growth and reproduction. Being large is considered to be advantageous, in females due to increased fecundity, and in males due to higher ability to compete for mates, while the cost of high growth is a reduced possibility to survive until the next mating season. Moor frog embryos originating from an acid population survived better under acid stress than embryos from a neutral population. Using quantitative genetic techniques I found strong maternal effects and small additive genetic variation for the traits in acid and non acid populations. The variation in acid stress tolerance owed largely to non-genetic effects. Females from acid localities lay larger eggs, which probably improves the performance of tadpoles under acid conditions. The trade-off between egg size and fecundity was stronger in acid populations indicating that females in acid populations reduced fecundity to increase offspring size. Finally, frogs from acidified environments were more asymmetric in skeletal traits further indicating the developmental stress created by acidification.
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Thomas, Scott. "DEMOGRAPHIC AND ENVIRONMENTAL INFLUENCES ON POPULATION DYNAMICS IN POND-BREEDING SALAMANDERS." University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron1590589607899457.
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Retamal, Diaz Francisco. "Impact des infrastructures sous la route sur les populations d’amphibiens." Master's thesis, Université Laval, 2020. http://hdl.handle.net/20.500.11794/67372.
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La modification d’habitats est un enjeu critique en conservation et la construction de routes y contribue grandement par la destruction et la fragmentation d’habitats. La construction de passages fauniques sous la route, ou « écopassages » peut réduire les impacts négatifs des routes sur les populations animales. Quatre écopassages à amphibiens associés à un réseau de clôtures d’exclusion ont été installés sous la route et sous une piste cyclable à proximité de sites de reproduction sur un tronçon de 22 km traversant le parc national Kouchibouguac au Nouveau-Brunswick. En 2017 et 2018, nous avons mené une étude afin d’évaluer l’impact de ces infrastructures sur les patrons spatiaux et temporels de mortalité routière ainsi que sur la survie des populations d’amphibiens. Nous avons émis l’hypothèse que les écopassages réduisent la mortalité des individus des populations d’amphibiens à proximité de ces dispositifs comparativement à des populations en bordure de routes dépourvues d’écopassages. Nous avons comparé les patrons de mortalité d’amphibiens sur la chaussée près des passages aux patrons de mortalité dans 10 segments dépourvus d’écopassages. Nous avons ensuite comparé la mortalité routière en 2017 et 2018 à celle pendant une période de 10 années avant la construction des écopassages (1995-2004). De plus, nous avons comparé la survie des populations d’amphibiens à l’aide de campagnes de capture-marquage-recapture (CMR) de Grenouille verte (Lithobates clamitans) à proximité des clôtures d’exclusion associées aux quatre écopassages ainsi qu’à un site sans écopassage. Les résultats obtenus indiquent que les mesures d’atténuation installées n’ont pas suffi à réduire les impacts de la route sur la mortalité routière et la survie des populations d’amphibiens étudiées. Nous n’avons pas observé de diminution de la mortalité routière en bordure des sites aménagés versus des sites non aménagés et entre la période avant et après l’installation des infrastructures. Le nombre d'individus observés sur la route variait avec les caractéristiques du paysage entourant la route. Le nombre d’individus augmentait avec la longueur moyenne des fossés de drainage contenant de l’eau en bord de route. De plus, le nombre d’individus diminuait avec l’augmentation du pourcentage de couverture de milieux humides à l’intérieur d’u rayon de de 300 m et avec la distance au milieu humide le plus proche. Le taux de survie des populations de grenouilles vertes n’était pas plus élevé aux sites aménagés qu’au site témoin. L’intégrité structurelle des clôtures d’exclusion, la faible densité d’écopassages et la diminution de l’intensité du trafic suivant la construction des écopassages pourraient expliquer l’absence de différence entre les sites aménagés et non aménagés. Nous recommandons une collaboration entre les ingénieurs routiers et les chercheurs dès les premières phases de planification de la construction des mesures d'atténuation afin de limiter autant que possible l'impact de la route et d’optimiser l’effet de ces structures.
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Webster, Janelle T. "Individual identification, disease monitoring and home range of Leiopelma hamiltoni." Thesis, University of Canterbury. Biological Sciences, 2004. http://hdl.handle.net/10092/1454.
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Amphibian populations are declining on a global scale and although disease outbreaks are a commonly accepted hypothesis they are not the only one. My aims for my thesis were to study the home range of Leiopelma hamiltoni, to determine whether a photographic database could be used to individual identified them and monitor the health status of the population. Habitat loss is a possible cause. For this reason monitoring an animals' home range is a possible method to detect early impacts the population is facing. By tracking 12 L. hamiltoni within a 12 m x 6 m grid on Maud Island, it was shown that the home range size can vary from 0.5 m2 to 25 m2 based on the minimum convex polygon method. However, to track multiple individuals it is important to be able to distinguish among frogs. The commonly used methods of identification, such as toe clipping, pose potentially detrimental effects. Therefore, non-invasive methods based on natural markings need to be established. Through the use of the dark pigmented patterns found on the skin of L. hamiltoni individuals can be identified on recapture with a mean accuracy of 93%. By developing a database to maintain the photographs used for individual identification, the database can also be used to monitor the status of the population. During 2003 numerous L. hamiltoni were observed with denuded patches predominantly on the facial region. By monitoring five individuals within the captive facility at the University of Canterbury it was discovered that frogs appear to be able to cure themselves. Through researching the home range requirements and developing a photographic database to monitor the population status of L. hamiltoni, it will aid in the management of ensuring the long-term survival of this archaic species of frog.
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Sutherland, Christopher. "A quantitative investigation of metapopulation dynamics in a naturally fragmented population of water voles Arvicola amphibius." Thesis, University of Aberdeen, 2013. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=198348.
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Mazerolle, Marc J. "Mouvements et reproduction des amphibiens en tourbières perturbées." Thesis, Université Laval, 2004. http://www.theses.ulaval.ca/2004/21842/21842.pdf.
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Les déclins de populations d’amphibiens ont généré de nombreux travaux sur les effets de la perte d’habitats variés, mais peu en milieux naturellement acides. Néanmoins, plusieurs tourbières du sud-est canadien sont perturbées par l’extraction de la tourbe. Dans le premier chapitre, j’ai comparé l’utilisation des milieux tourbeux par les amphibiens à celle des milieux non tourbeux. Dans les quatre chapitres subséquents, j’ai quantifié les effets de l’extraction de la tourbe sur l’utilisation des étangs de tourbières par les amphibiens et mesuré les contraintes liées à leurs déplacements sur des surfaces exploitées. Les résultats indiquent que les amphibiens utilisent les tourbières surtout comme sites d’estivage. De plus, l’intensité de l’exploitation influence la fréquentation des étangs, mais la quantité et la proximité d’habitats complémentaires (i.e., étangs adjacents, forêt) semblent réduire ces effets. Finalement, les surfaces arides associées à certaines activités anthropiques telles que l’exploitation des tourbières ou l’agriculture, entravent les déplacements des grenouilles, bien que ces effets puissent être atténués par la présence de canaux de drainage.Global amphibian population declines have generated numerous studies on the effects of habitat loss, but few have been conducted in naturally-acidic environments. Nevertheless, many peatlands are undergoing peat extraction in southeastern Canada. Through five chapters, I have studied the use of bog habitats by amphibians, quantified the effects of peat extraction on amphibian occurrence at bog ponds, and measured the constraints associated with movements over mined surfaces. Bogs were less productive breeding sites than less acidic upland sites, but were used by adults and juveniles following breeding outside bogs. Bog ponds on surfaces actively mined for peat offered suboptimal habitats to green frogs (Rana clamitans), whereas bog ponds on surfaces drained for future peat mining, characterized by the presence of drainage ditches and vegetation, provided supplementary frog habitat. However, this positive effect was only temporary, as these surfaces were to be eventually mined. In a study conducted at a larger scale and focusing on bog ponds on unmined surfaces, I showed the importance of the amount and proximity of complementary habitats (i.e., adjacent ponds, forest) on the spatial distribution of amphibian presence at ponds. Moreover, frog movement experiments revealed that frogs translocated on barren peat surfaces had a lower probability of homing successfully than those translocated at a similar distance on an undisturbed surface, and that dehydration risks were the lowest on natural surfaces with vegetation cover. No reproduction occurred in drainage ditches, although frog survival in these structures was high. In addition, ditches did not impede the movements of individuals. Globally, results indicate that amphibians use bogs mostly as summering sites. Furthermore, peat mining intensity influences the occurrence of amphibians at ponds, but the proximity and amount of complementary habitats could mitigate these effects. Finally, barren surfaces associated with certain human disturbances such as peat mining and agriculture impede frog movements, although drainage ditches, particularly those containing water, may facilitate movements across these hostile environments.
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Bouffard, Jeremie. "Effects of a Neonicotinoid Insecticide and Population Density on Behaviour and Development of Wood Frogs (Lithobates sylvaticus)." Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/42390.
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Amphibians have been facing global declines over the last decades due to direct and indirect effects of anthropogenic activities. One of the leading causes is environmental contamination, particularly that of waterbodies which are used by many amphibian species for reproduction, development, and adult life. An important source of contamination comes from agricultural runoffs of pesticides such as neonicotinoids, which are known to alter anuran survival, behaviour, predation stress response, and development. However, few studies have investigated the possible interactions between neonicotinoids and natural environmental stressors which could alter the strength and direction of observed neonicotinoid effects. This study investigated how a concentration of imidacloprid (a neonicotinoid) measured in surface waters interacted with high population density, an important environmental stressor, to influence behaviour and development across metamorphosis in wood frogs (Lithobates sylvaticus) known to breed in agricultural landscapes. I reared tadpoles in a fully crossed design experiment, between two densities (0.33 and 1 tadpole/L) and clean vs contaminated water (10 µg/L imidacloprid). Behaviours were measured in the absence and presence of predation cues using open-field tests at three distinct developmental stages, up to the metamorph stage. I found that imidacloprid did not interact with population density or independently affect behaviours in the absence of predation cues. However, individuals raised at high density compared with low density were more active at an early developmental stage but less active at metamorphic climax. Furthermore, both density and imidacloprid independently decreased the natural behavioural response (i.e., “freezing”) of tadpoles to predation cues. Both treatments also slightly accelerated metamorphosis while only density altered final mass at metamorphosis. Finally, I found that distance travelled was weakly repeatable between aquatic stages but not repeatable across metamorphosis, a pattern that was not affected by treatments. This study provides novel insights on the ecotoxicology of imidacloprid in the presence of a natural stressor, highlighting the importance of including behavioural assays and stressors in studies of amphibian ecotoxicology.
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Fontana, Rodrigo Barbosa. "Atributos ecológicos de anuros neotropicais: o que podem predizer?" reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/180577.
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O risco de extinção e o declínio populacional de muitas espécies animais na região neotropical estão fortemente relacionados aos processos antrópicos, como a conversão ambiental, mas também aos fatores intrínsecos aos próprios indivíduos, como os atributos. Os anuros correspondem ao grupo vertebrado mais ameaçado atualmente, sofrendo com sérios declínios populacionais. Este trabalho buscou avaliar quais os atributos dos anfíbios neotropicais podem predizer: i) as categorias de ameaça e tendências populacionais destas espécies e ii) a ocorrência de anuros em um ambiente modificado, de matriz agrícola. Para a predição de categorias de ameaça e tendências populacionais utilizamos um banco de dados com atributos de habitat e modos reprodutivos de 3196 espécies de anuros neotropicais. Verificamos que espécies com modos reprodutivos terrestres e desenvolvimento direto tem uma maior tendência a estarem em declínio. Além disso, verificamos que embora os atributos sejam filogeneticamente estruturados, o grau de ameaça parece ser independente de suas histórias evolutivas. Para identificar possíveis relações entre atributos ecológicos e morfológicos de anuros em uma paisagem agrícola no sul do Brasil, registramos a anurofauna com uso de armadilhas de interceptação e queda e procuras ativas em três diferentes distâncias da borda em um ambiente florestal e em uma matriz agrícola. Verificamos que principalmente os atributos ecológicos, como o modo reprodutivo (tanto terrestre como aquático) e o hábito estão relacionados com a ocorrência destas espécies no sistema agrícola, assim como encontramos diferenças entre os atributos morfológicos ao longo do gradiente de distância. Ambos os resultados podem auxiliar na tomada de decisões em planos e projetos de conservação de anuros neotropicais.The extinction risk and population decline of many animal species in neotropical region are strongly related to anthropic processes, such as environmental conversion, but they are also related to intrinsic factors such as traits. Anurans correspond to the most endangered vertebrate group, suffering serious population declines. This work aimed to evaluate which neotropical anurans traits can predict: i) the categories of threat and population trends of species, and ii) the occurrence of anuran species in modified environments, such as the agricultural matrix. First, we compiled data to 3196 neotropical anuran species. We emphasized the importance of habitat and reproductive modes in threat classifications, as well as verified that species with terrestrial reproductive modes and direct development are more likely to be declining. We also found that although anurans traits being phylogenetically structured, the degree of threat seems to be independent from their evolutionary histories. In addition, to identify possible relation among ecological and morphological anuran traits with agricultural landscape in southern Brazil, we studied the anurofauna using pitfall traps and active searches at three different border distances in a forest environment and in an agricultural matrix. We verified that mostly of the ecological traits, such as the reproductive mode (both terrestrial and aquatic) and the habit, are related to the occurrence of determined species in the agricultural system. And we also found differences among the morphological traits observed through the distance gradient from the border. Therefore, both results present practical importance since it can help herpetologists to making decision about neotropical anurans conservation.