Dissertations / Theses on the topic 'Freshwater dispersal'

The main goal of this thesis was to improve the knowledge on the mechanisms involved on Human dispersal of freshwater invasive fauna, contributing for the management of these problematic species. Several vectors were investigated, both accidental and intentional, from a freshwater invaders list that included some of the worse species. It was found that the red swamp crayfish and the signal crayfish presented desiccation survival capacities compatible with long-distance human-mediated dispersal. Off-road vehicles constituted a viable accidental vector for invasive macroinvertebrates, like the red swamp crayfish and the bladder snail. Live bait capture using dip nets and crayfish trapping constitute viable vectors for invasive freshwater macrofauna dispersal. The former is more related with accidental transport of small invasive organisms, and the latter is mostly related with intentional transport of invasive fish species. The importance of the angling web forums as a useful tool to help detection of non-native fish species was demonstrated with the first record of European Perch, a non-native fish in continental Portugal. Freshwater anglers from Portugal and Spain presented preference for invasive fish species, similar mobility, low incidence of live bait use and similar perception of biological freshwater invasions processes and impacts. Differences among countries were found for angler's activity patterns throughout the year and motivations for introductions. Zebra mussel larvae desiccation survival is compatible with long-distance overland dispersal. Its transport by natural vectors, like ducks, or human vectors like fishing tackle, such as waders and keep nets is viable. Yet, when comparing both types of vectors, fishing tackle presented a higher propensity to spread zebra mussel larvae than ducks; Dispersão de fauna invasiva dulçaquícola pelo Homem Resumo: O principal objetivo desta tese foi melhorar o conhecimento dos mecanismos envolvidos na dispersão de fauna dulçaquícola invasiva pelo homem, contribuindo assim para a gestão destas espécies problemáticas. Investigaram-se vários vetores, quer acidentais quer intencionais de uma lista de invasores dulçaquícolas que incluem algumas das piores espécies. Verificou-se que o lagostim vermelho e o lagostim sinal possuem uma capacidade de sobrevivência à dessecação compatível com a sua dispersão a longa distância pelo Homem. Os veículos todo-o-terreno constituem um vetor viável para macroinvertebrados invasivos como o lagostim vermelho e o caracol aquático. A captura de isco vivo com recurso a camaroeiro e o uso de armadilhas para a captura de lagostim constituem vetores viáveis de dispersão para a macrofauna dulçaquícola, sendo que o primeiro está relacionado com o transporte acidental de pequenos organismos invasores e o segundo com transporte intencional de peixes invasores. Através do primeiro registo em Portugal Continental de Perca-europeia, uma espécie não-nativa, demostrou-se a importância de fóruns on-line de pesca desportiva como uma ferramenta útil para a deteção de peixes não-nativos. Os pescadores dulçaquícolas de Portugal e Espanha apresentam preferência por espécies de peixes invasores, similar mobilidade, baixa incidência no uso de isco vivo e similar perceção dos processos e impactos das invasões biológicas dulçaquícolas. Detetaram-se diferenças entre países nos padrões de atividade dos pescadores durante o ano e na motivação para as introduções. A sobrevivência à dessecação de larvas de mexilhão-zebra é compatível com o seu transporte a longas distâncias fora de água, sendo viável o seu transporte quer por vetores naturais, como patos, quer humanos como equipamento de pesca, como botas altas e redes de retenção. No entanto, quando se comparam ambos os tipos de vetores, o equipamento de pesca apresenta maior propensão que os patos para dispersar larvas de mexilhão-zebra.

Thesis (Ph. D.)--Michigan State University. Dept. of Zoology. Program in Ecology, Evolutionary Biology and Behavior, 2006.
Title from PDF t.p. (viewed on Nov. 20, 2008) Includes bibliographical references (p. 161-168). Also issued in print.

Freshwater systems offer important opportunities to investigate the consequences of intrinsic biological and extrinsic environmental factors on the distribution of genetic variation, and hence population genetic structure. Drainages serve to isolate populations and so preserve historical imprints of population processes. Nevertheless, dispersal between and within drainages is important if the biology of the species confers a good dispersal capability. Knowledge of the population genetic structure or phylogeographic patterns of Australia's freshwater fish fauna is generally depauperate, and the present study aimed to increase this knowledge by investigating patterns of genetic diversity in three Australian species of freshwater fish. I was interested in the relative importance of dispersal capability, the hierarchical nature of stream structure and the consequences of earth history events on patterns of genetic diversity among populations. I examined three species from three families of Australian freshwater fish, Pseudomugil signifer (Pseudomugilidae), Craterocephalus stercusmuscarum (Atherinidae) and Hypseleotris compressa (Gobiidae). These species are abundant, have wide overlapping distributions and qualitatively different dispersal capabilities. I was interested in attempting to unravel how the biological, environmental and historical factors had served to influence the patterns and extent of genetic diversity within each species, thereby inferring some of the important evolutionary processes which have affected Australia's freshwater fauna. I used allozyme and 500-650bp sequences from the ATPase6 mitochondrial DNA (mtDNA) gene to quantify the patterns of genetic variation at several hierarchical levels: within populations, among populations within drainages and among drainages. I collected fish at several spatial scales, from species wide to multiple samples within drainages; samples were collected from the Northern Territory, Queensland and New South Wales. The species with the highest potential for dispersal, H. compressa, exhibited the lowest levels of genetic differentiation as measured at several allozyme loci (H. compressa: FST=0.014; P. signifer FST=0.58; C. stercusmuscarum FST=0.74). Populations of H. compressa also had low levels of mtDNA differentiation, with many recently derived haplotypes which were widespread along the coast of Queensland. This suggested either considerable gene flow occurs or recent demographic change in the populations sampled. As there was no relationship between geographic distance and genetic differentiation, the populations appeared to be out of genetic drift - gene flow equilibrium, assuming the two-dimensional stepping stone model of gene flow. Estimating contemporary gene flow was thus difficult. It was apparent that there has been a recent population expansion and / or contraction of H. compressa populations. It was concluded that there has been considerably more connectivity among populations of H. compressa in the recent past than either of the other study species. Populations of P. signifer showed considerable genetic subdivision at different hierarchical levels throughout the sampled range, indicating gene flow was restricted, especially between separate drainages. Two widely divergent regional groups which had high ATPase6 sequence divergence and approximately concordant patterns at allozyme loci were identified. Interestingly, the groups mirrored previous taxonomic designations. There was also significant subdivision among drainages within regional groups. For example, the adjacent Mulgrave-Russell and Johnstone drainages had individuals with haplotypes that were reciprocally monophyletic and had large allozyme frequency differences. This allowed me to examine the patterns of genetic differentiation among populations within drainages of two essentially independent, but geographically close systems. There was as much allozyme differentiation among populations within subcatchments as there was between subcatchments within drainages, and significant isolation by distance among all populations sampled within a drainage. This suggested that the estuarine confluence between subcatchments was not a barrier to P. signifer, but that distance was an important component in the determination of the distribution of genetic diversity within drainages in P. signifer. There were three main areas of investigation for C. stercusmuscarum: comparing upland and lowland streams of the drainages in north Queensland, investigating the consequences of eustasy on coastal margin populations and examining the intriguing distribution of the two putative sub species, C. s. stercusmuscarum and C. s. fulvus in south east Queensland. First, as populations in upland areas of east coast flowing rivers are above large discontinuities in the river profile, their occurrence is presumably the result of gene flow to and / or from lowland areas, or the result of invasions via the diversion of western flowing rivers. Concordant patterns at both genetic markers revealed that the latter possibility was the most likely, with fixed allozyme differences between upland and lowland populations, and large mtDNA sequence divergence. Indeed, it appeared that there may have been two independent invasions into the upland areas of rivers in North Queensland. Second, lowland east coast populations also had large, although not as pronounced, levels of population subdivision. Lack of isolation by distance, but with a concomitant high level of genetic differentiation among many comparisons, was consistent with a scenario of many small, isolated subpopulations over the range. Interestingly, widespread populations in central Queensland coastal populations (drainages which receive the lowest rainfall) were relatively genetically similar. This was consistent with the widest part of the continental shelf which at periods of lower sea level apparently formed a large interconnected drainage, illustrating the effect of eustatic changes on populations inhabiting a continental margin. Third, putative C. s. fulvus in lowland coastal Queensland drainages were genetically more similar to a population of C. s. fulvus collected from a tributary of the Murray-Darling (western flowing) than they were to adjacent putative C. s. stercusmuscarum. This implied that populations in south east Queensland, north to approximately the Burnett River, appeared to be derived from western flowing streams, and not via dispersal from other lowland east coast populations. Determining the relative importance of intrinsic and extrinsic factors to the development of population genetic structure is a difficult task. The present study demonstrated that the species with the highest dispersal potential had the lowest levels of genetic differentiation, waterfalls can limit gene flow, eustasy acts to join and separate populations leading to complex genetic patterns and that drainage rearrangements are important in determining the distribution of genetic diversity of populations now inhabiting isolated drainages. A difficulty with generalising about population genetic structure in obligate freshwater animals is the unique history of not only each drainage, but also the streams within that drainage and the idiosyncratic biological dynamics of the populations inhabiting those drainages.

Meiofauna, and especially marine nematodes are common in sediments around the world. Despite very wide ranging distributions in many nematode species, little is presently known about their dispersal mechanisms shaping these patterns. Rafting, and perhaps ballast water transport has been suggested as viable means for nematode long-range transport. On a much smaller scale other processes have been suggested for their dispersal. They generally include some form of passive suspension into the water column and later on a passive, haphazard settling back towards the bottom.

Small-scale phenomena in nematode dispersal were studied by conducting a series of studies at Askö field station, Trosa Archipelago, Baltic proper. Studied aspects were one case of macrofaunal influence on nematode dispersal rate, using an amphipod, Monoporeia affinis as disturbing agent, and three different studies on mechanisms related to settling. The experiments were conducted both in laboratory and field settings.

The amphipod Monoporeia affinis did not exert any influence on the dispersal rate in the nematodes. The nematode dispersal was only an effect of time, in the aspect that the more time that past, the more nematodes dispersed from their place of origin. The settling experiments revealed that nematodes do have an active component in their settling behaviour, as they were able to exert influence on the spot where they were to settle. They were able to choose settling spot in response to the food quality of the sediment. It also became evident that contrary to common belief, nematodes are able to extend their presence in the water column far beyond the times that would be predicted considering settling velocities and hydrodynamic conditions alone.

Animal hosts provide associated microorganisms with suitable ecological niches in their intestines. Microbes help their hosts to digest food, protect against pathogens, and influence the host’s metabolisms. Compositional variation of gut microbial communities is common among hosts, and may affect the health status of hosts. Diet and genetic factors are well known to influence the assembly of gut microbial communities. This thesis focuses on disentangling the contributions of factors including host genetics (sex), diet, environment, and other ecological processes to the assembly of gut microbial communities in freshwater fish. The association between gut microbial communities and fish condition is also evaluated in this thesis. Applying metacommunity theory, we found environmental factors including fish habitat, fish species, their diet, dispersal factors including microbes from fish diet, and ecological drift contributed to the assembly of fish gut microbial communities. The proportion of their contribution varied between fish species, where ecological drift explained more in perch than in roach. Under natural conditions fish populations face the risk of predation, which can induce competition and impose predation stress within prey individuals. This can therefore lead to changes in their diet qualities and quantities. In this thesis, it was shown that fish diet in terms of qualities and quantities significantly influenced the overall gut microbial composition, and this influence was dependent on fish sex, a host genetic factor. Predation stress was also suggested to significantly decrease the species richness. Furthermore, when fish were experiencing a diet shift, we showed that different bacterial phyla from novel food had different colonization success in the intestine, and this colonization success was positively influenced by predation stress. Fish condition was suggested in this thesis to be affected by gut microbial composition, especially by the contributions of the bacterial phyla Tenericutes and Actinobacteria.

Abstract Freshwater ecosystems are severely threatened by a variety of anthropogenic stressors. In order to keep track with at least part of the changes, it is important to efficiently assess and monitor freshwater biological diversity. Biological assessment programs are developed to detect human-induced changes in the ecological state of aquatic systems. These programs typically rely on the assumption that environmental conditions are the sole drivers of biological communities occupying a site and, thus, these local communities would correctly inform about environmental conditions. Recently, this background principle of current bioassessment methods has faced some criticism, stemming from the idea that community structuring is a more complex process than just a mere result of local environmental conditions. In this thesis, I studied the natural and anthropogenic drivers of freshwater biodiversity. I was particularly interested if the various biodiversity metrics studied showed any spatial patterns and if so, for which reasons these patterns might occur. To obtain a comprehensive picture of spatial patterns in biodiversity, I studied multiple spatial contexts, biological groups and indices. I found that environmental conditions were not the only drivers of freshwater biodiversity. Instead, different spatial patterns, likely stemming from dispersal processes, were surprisingly powerful drivers of aquatic communities and index values derived from them. The spatial context (i.e. spatial extent and connectivity) of the aquatic study systems likely played a major role in structuring biodiversity. I also found that the distinct biological groups and indices studied were partly related to different predictor variables. The findings of this thesis are of importance to the development of new bioassessment methods. The results of this thesis also suggest that the spatial context of the study setting should be acknowledged when interpreting results based on current bioassessment methods
Tiivistelmä Makeanveden ekosysteemit ovat hyvin alttiita ihmistoiminnalle. Ekosysteemissä mahdollisesti tapahtuvien muutosten havaitseminen vaatii tehokkaita vesistöjen ekologisen tilan ja luonnon monimuotoisuuden arviointi- ja seurantamenetelmiä. Näiden menetelmien toimintaperiaatteen yleisenä tausta-ajatuksena on, että biologiset yhteisöt määräytyvät paikallisten ympäristöolojen mukaan. Tietyn paikan yhteisön oletetaan siis heijastavan kyseisen paikan ympäristön tilaa. Viime aikoina tausta-ajatus paikallisten ympäristöolojen merkityksestä ainoana eliöyhteisöjä muovaavana tekijänä on kuitenkin kohdannut kritiikkiä. Kriitikot painottavat, että biologisten yhteisöjen rakenteeseen vaikuttavat monet muutkin asiat kuin paikalliset ympäristöolosuhteet ja niissä tapahtuvat ihmisperäiset muutokset. Väitöskirjassani tutkin sisävesien luonnon monimuotoisuuteen vaikuttavia tekijöitä. Olin erityisen kiinnostunut siitä, näkyykö tutkituissa biologisissa parametreissa maantieteellisessä tilassa ilmeneviä spatiaalisia säännönmukaisuuksia. Saadakseni mahdollisimman laaja-alaisen käsityksen luonnon monimuotoisuudessa esiintyvistä spatiaalisista säännönmukaisuuksista, tutkin useaa spatiaalista kontekstia, eliöryhmää ja indeksiä. Tutkimuksessa selvisi, että paikalliset ympäristöolosuhteet eivät ole ainoita luonnon monimuotoisuuteen vaikuttavia tekijöitä. Erilaiset spatiaaliset säännönmukaisuudet, todennäköisesti eliöiden levittäytymiseen liittyvien seikkojen aiheuttamina, olivat yllättävän yleisiä makeiden vesien eliöyhteisöjen rakenteessa ja niihin perustuvien indeksien arvoissa. Tutkimussysteemien spatiaalinen konteksti (alueen laajuus ja paikkojen väliset spatiaaliset suhteet) selvästi vaikutti luonnon monimuotoisuutta kuvastavien indeksien arvojen vaihteluun. Lisäksi selvisi, että eri eliöryhmät ja indeksit olivat useimmiten liitoksissa hyvin erilaisiin selittäviin muuttujiin, osoittaen, että nämä mittarit kuvastavat eri asioita. Väitöskirjassa esitetyt havainnot on tärkeää huomioida vesistöjen ekologisen tilan ja luonnon monimuotoisuuden arviointi- ja seurantamenetelmiä kehitettäessä. Spatiaalisen kontekstin merkitys olisi hyvä huomioida myös nykyisten arviointi- ja seurantamenetelmien tuottamien tulosten tulkinnassa

The Giant Long-Armed Prawn, Macrobrachium lar is a freshwater species native to the Indo-Pacific. M. lar has a long-lived, passive, pelagic marine larval stage where larvae need to colonise freshwater within three months to complete their development. Dispersal is likely to be influenced by the extensive distances larvae must transit between small oceanic islands to find suitable freshwater habitat, and by prevailing east to west wind and ocean currents in the southern Pacific Ocean. Thus, both intrinsic and extrinsic factors are likely to influence wild population structure in this species. The present study sought to define the contemporary broad and fine-scale population genetic structure of Macrobrachium lar in the south-western Pacific Ocean. Three polymorphic microsatellite loci were used to assess patterns of genetic variation within and among 19 wild adult sample sites. Statistical procedures that partition variation implied that at both spatial scales, essentially all variation was present within sample sites and differentiation among sites was low. Any differentiation observed also was not correlated with geographical distance. Statistical approaches that measure genetic distance, at the broad-scale, showed that all south-western Pacific Islands were essentially homogeneous, with the exception of a well supported divergent Cook Islands group. These findings are likely the result of some combination of factors that may include the potential for allelic homoplasy, through to the effects of sampling regime. Based on the findings, there is most likely a divergent M. lar Cook Islands clade in the south-western Pacific Ocean, resulting from prevailing ocean currents. Confirmation of this pattern will require a more detailed analysis of nDNA variation using a larger number of loci and, where possible, use of larger population sizes.

Freshwater systems offer important opportunities to investigate the consequences of intrinsic biological and extrinsic environmental factors on the distribution of genetic variation, and hence population genetic structure. Drainages serve to isolate populations and so preserve historical imprints of population processes. Nevertheless, dispersal between and within drainages is important if the biology of the species confers a good dispersal capability. Knowledge of the population genetic structure or phylogeographic patterns of Australia's freshwater fish fauna is generally depauperate, and the present study aimed to increase this knowledge by investigating patterns of genetic diversity in three Australian species of freshwater fish. I was interested in the relative importance of dispersal capability, the hierarchical nature of stream structure and the consequences of earth history events on patterns of genetic diversity among populations. I examined three species from three families of Australian freshwater fish, Pseudomugil signifer (Pseudomugilidae), Craterocephalus stercusmuscarum (Atherinidae) and Hypseleotris compressa (Gobiidae). These species are abundant, have wide overlapping distributions and qualitatively different dispersal capabilities. I was interested in attempting to unravel how the biological, environmental and historical factors had served to influence the patterns and extent of genetic diversity within each species, thereby inferring some of the important evolutionary processes which have affected Australia's freshwater fauna. I used allozyme and 500-650bp sequences from the ATPase6 mitochondrial DNA (mtDNA) gene to quantify the patterns of genetic variation at several hierarchical levels: within populations, among populations within drainages and among drainages. I collected fish at several spatial scales, from species wide to multiple samples within drainages; samples were collected from the Northern Territory, Queensland and New South Wales. The species with the highest potential for dispersal, H. compressa, exhibited the lowest levels of genetic differentiation as measured at several allozyme loci (H. compressa: FST=0.014; P. signifer FST=0.58; C. stercusmuscarum FST=0.74). Populations of H. compressa also had low levels of mtDNA differentiation, with many recently derived haplotypes which were widespread along the coast of Queensland. This suggested either considerable gene flow occurs or recent demographic change in the populations sampled. As there was no relationship between geographic distance and genetic differentiation, the populations appeared to be out of genetic drift - gene flow equilibrium, assuming the two-dimensional stepping stone model of gene flow. Estimating contemporary gene flow was thus difficult. It was apparent that there has been a recent population expansion and / or contraction of H. compressa populations. It was concluded that there has been considerably more connectivity among populations of H. compressa in the recent past than either of the other study species. Populations of P. signifer showed considerable genetic subdivision at different hierarchical levels throughout the sampled range, indicating gene flow was restricted, especially between separate drainages. Two widely divergent regional groups which had high ATPase6 sequence divergence and approximately concordant patterns at allozyme loci were identified. Interestingly, the groups mirrored previous taxonomic designations. There was also significant subdivision among drainages within regional groups. For example, the adjacent Mulgrave-Russell and Johnstone drainages had individuals with haplotypes that were reciprocally monophyletic and had large allozyme frequency differences. This allowed me to examine the patterns of genetic differentiation among populations within drainages of two essentially independent, but geographically close systems. There was as much allozyme differentiation among populations within subcatchments as there was between subcatchments within drainages, and significant isolation by distance among all populations sampled within a drainage. This suggested that the estuarine confluence between subcatchments was not a barrier to P. signifer, but that distance was an important component in the determination of the distribution of genetic diversity within drainages in P. signifer. There were three main areas of investigation for C. stercusmuscarum: comparing upland and lowland streams of the drainages in north Queensland, investigating the consequences of eustasy on coastal margin populations and examining the intriguing distribution of the two putative sub species, C. s. stercusmuscarum and C. s. fulvus in south east Queensland. First, as populations in upland areas of east coast flowing rivers are above large discontinuities in the river profile, their occurrence is presumably the result of gene flow to and / or from lowland areas, or the result of invasions via the diversion of western flowing rivers. Concordant patterns at both genetic markers revealed that the latter possibility was the most likely, with fixed allozyme differences between upland and lowland populations, and large mtDNA sequence divergence. Indeed, it appeared that there may have been two independent invasions into the upland areas of rivers in North Queensland. Second, lowland east coast populations also had large, although not as pronounced, levels of population subdivision. Lack of isolation by distance, but with a concomitant high level of genetic differentiation among many comparisons, was consistent with a scenario of many small, isolated subpopulations over the range. Interestingly, widespread populations in central Queensland coastal populations (drainages which receive the lowest rainfall) were relatively genetically similar. This was consistent with the widest part of the continental shelf which at periods of lower sea level apparently formed a large interconnected drainage, illustrating the effect of eustatic changes on populations inhabiting a continental margin. Third, putative C. s. fulvus in lowland coastal Queensland drainages were genetically more similar to a population of C. s. fulvus collected from a tributary of the Murray-Darling (western flowing) than they were to adjacent putative C. s. stercusmuscarum. This implied that populations in south east Queensland, north to approximately the Burnett River, appeared to be derived from western flowing streams, and not via dispersal from other lowland east coast populations. Determining the relative importance of intrinsic and extrinsic factors to the development of population genetic structure is a difficult task. The present study demonstrated that the species with the highest dispersal potential had the lowest levels of genetic differentiation, waterfalls can limit gene flow, eustasy acts to join and separate populations leading to complex genetic patterns and that drainage rearrangements are important in determining the distribution of genetic diversity of populations now inhabiting isolated drainages. A difficulty with generalising about population genetic structure in obligate freshwater animals is the unique history of not only each drainage, but also the streams within that drainage and the idiosyncratic biological dynamics of the populations inhabiting those drainages.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Australian School of Environmental Studies
Full Text

Stream fish assemblages exist within stream networks defined by the size and proximity of connected streams (i.e., stream network topology). The spatial position of sites within stream networks may therefore regulate opportunities for fish dispersal to access distant resources or colonize "new" habitats. Such inter-stream dispersal dynamics will influence local fish assemblage structure and the vulnerability of local assemblages to anthropogenic stressors. In this dissertation, I explored the effects of stream network topology on fish assemblage structure in the mid-Atlantic highlands, USA and tested the hypothesis that dispersal would affect the sensitivity of fish-based environmental quality assessments (i.e., bioassessments). In chapter 1, I evaluated the effects of stream networks by comparing fish assemblages between sites with and without large downstream confluences (>3rd order) in western Virginia, USA (i.e., mainstem tributaries and headwater tributaries, respectively). I found that local species richness was higher in mainstem tributaries than headwater tributaries and that these effects could not be explained by variation in local environmental habitat conditions. In chapter 2, I developed and applied a continuous model of stream network topology to explore the effects of downstream size and proximity on local fish assemblage structure within the mid-Atlantic highlands. I found that fish assemblage structure (i.e., Bray-Curtis distances in species abundance) was significantly related to variation in stream network topology up to approximately 9 fluvial km from sites. Chapters 3 and 4 explored the implications of inter-stream dispersal for fish bioassessments. In Chapter 3, I identified 10 fish metrics that corresponded predictably to environmental stressors in the mid-Atlantic highlands. However, headwater tributary assemblages showed stronger relations to local environmental quality than mainstem tributaries, consistent with the hypothesis of riverine dispersal. In Chapter 4, I compared the effects of stream network topology on fish and benthic macroinvertebrate assemblages. Fish metrics were influenced by the size and proximity of connected streams but benthic macroinvertebrate metrics were not. This finding suggests that stream fishes may complement benthic macroinvertebrate bioassessments by indicating environmental conditions at larger spatial grains.
Ph. D.

One of ecology’s primary goals is to comprehend biodiversity and its patterns of distribution over space and time. Since microorganisms play a pivotal role in key ecological processes, the diversity of microbial communities may have important implications for the stability and functioning of Earth’s ecosystems. Thus, it is of utmost importance to develop a theoretical foundation but also a conceptual understanding for the mechanisms that generate and maintain microbial diversity. The aim of this thesis is to investigate to what extent local freshwater bacterioplankton diversity, i.e. richness and community composition, is structured by local environmental interactions and/or regional processes. The key objective is to identify ecological linkages between lake bacterioplankton and bacterial communities in connected streams and the surrounding terrestrial landscape, thereby applying a metacommunity approach. To do so, I studied several natural lake bacterioplankton assemblies within different regions of Sweden and assessed both local environmental properties and regional parameters (e.g. dispersal, landscape position). The genetic composition of freshwater bacterioplankton diversity was determined by means of terminal-restriction fragment length polymorphism or 454 pyrosequencing. From the review on the biogeography of bacterioplankton in inland waters it became clear that microbial diversity and its spatial distribution are governed by a complex interplay of both local and regional drivers. In one case, freshwater bacterioplankton communities were structured by local environmental conditions rather than by regional dispersal processes. These local environmental conditions seemed to be equally important in controlling both the total bacterioplankton community and its active fraction. In a study of bacterioplankton communities from five different regions, locally abundant aquatic bacteria were shown to be also regionally widespread, a pattern predicted by neutral theory. Yet, this degree of similarity decreased with increasing environmental heterogeneity. In another study, bacterioplankton richness was controlled mostly by nutrient content, indicating that productivity exerted influence on bacterioplankton richness. However, landscape position and productivity covaried, suggesting that the landscape dictates environmental properties, which then directly structure local bacterioplankton richness. Finally, a review synthesising results from empirical metacommunity approaches and comparing these to theory showed that yet a gap between empirics and theory exists. To conclude, local bacterioplankton diversity appeared to be mainly structured by local environmental properties. However, signatures of neutral processes driving local bacterioplankton community assembly were also recorded.

Ecological models have problems showing the positive relationship between diversity and stability found in nature. Theory states that complex food webs have high extinction risks and low stability. However, persistent food webs found in nature are large and complex containing many interconnections between species. There are many possible mechanisms enabling persistent food webs such as; complex interaction patterns, asynchronous fluctuations of species densities, environmental fluctuations and spatial distribution. These factors have not been used in classical models. In this study, coloured environmental 1/f noise and dispersal between subpopulations were incorporated into a diamond shaped food web based on a model by Vasseur and Fox 2007. Contradictions between theoretical and empirical results regarding food webs can be resolved by detailed analyses of models, withholding stabilizing mechanisms. Weak environmental 1/f noise generated an increased coefficient of stability but the stabilizing effect of noise can be questioned because of a decreased mean food web biomass and reduced stabilizing effect when reddened. However, detailed studies of the food web revealed that noise can redistribute density proportions between species, evading lowest species density and thereby increase food web resistance to demographic stochasticity and catastrophes. Noise induced density proportion shifts imply that large population sizes are no insurance towards future increase in environmental variance. Synchrony of species environmental responses and dispersal between subpopulations can both have major influences on stability and extinction risk of smaller food webs indicating that spatial structure could be one of the dominating factors stabilizing complex food webs found in nature.

This thesis examines the relative importance of local conditions, dispersal and dynamics of the trees on epiphyte distribution patterns and colonization-extinction dynamics. Study species are the mosses Orthotrichum speciosum and O. obtusifolium, and the red-listed Neckera pennata. The thesis also includes an attempt to parameterize a model for a lichen metapopulation (Lobaria pulmonaria) in a dynamic landscape, based on only presence/absence data of the epiphyte and its host trees.

The results show that epiphyte colonization of trees is affected by both local conditions, and by connectivity to occupied trees. The positive effect of connectivity, implying a restricted dispersal range, was established by both demographic and genetic studies. The important local conditions were tree diameter and vitality, and shade. Local extinctions from trees occurred among small trees with low local epiphyte abundance, but more often, were the results of tree fall.

The observed importance of connectivity on epiphyte colonization agrees with the assumptions of the classic metapopulation model. However, the classic metapopulation model assumes that the landscape is static, and that local extinctions occur for stochastic reasons. The dynamics of epiphytes are different. A new conceptual model is therefore suggested, the patch-tracking metapopulation model. It differs from the classic metapopulation model in that it includes dynamics of the patches, and in that local extinctions only occur as patches are destroyed.

Simulations of the dynamics of N. pennata showed that its future metapopulation size will be overestimated unless the dynamics of the trees are accounted for. The simulation results further suggest that the dynamics of N. pennata can be characterised by the patch-tracking metapopulation model.

The attempt to parameterize the L. pulmonaria metapopulation model showed that more information are required for rigorous parameterization, preferably of the past historic fire regime.

The potential restriction to effective dispersal and gene flow caused by habitat fragmentation can apply to multiple levels of evolutionary scale; from the fragmentation of ancient supercontinents driving diversification and speciation on disjunct landmasses, to the isolation of proximate populations as a result of their inability to cross intervening unsuitable habitat. Investigating the role of habitat fragmentation in driving diversity within and among taxa can thus include inferences of phylogenetic relationships among taxa, assessments of intraspecific phylogeographic structure and analyses of gene flow among neighbouring populations. The proposed Gondwanan clade within the chironomid (non-biting midge) subfamily Orthocladiinae (Diptera: Chironomidae) represents a model system for investigating the role that population fragmentation and isolation has played at different evolutionary scales. A pilot study by Krosch et al (2009) indentified several highly divergent lineages restricted to ancient rainforest refugia and limited gene flow among proximate sites within a refuge for one member of this clade, Echinocladius martini Cranston. This study provided a framework for investigating the evolutionary history of this taxon and its relatives more thoroughly. Populations of E. martini were sampled in the Paluma bioregion of northeast Queensland to investigate patterns of fine-scale within- and among-stream dispersal and gene flow within a refuge more rigorously. Data was incorporated from Krosch et al (2009) and additional sites were sampled up- and downstream of the original sites. Analyses of genetic structure revealed strong natal site fidelity and high genetic structure among geographically proximate streams. Little evidence was found for regular headwater exchange among upstream sites, but there was distinct evidence for rare adult flight among sites on separate stream reaches. Overall, however, the distribution of shared haplotypes implied that both larval and adult dispersal was largely limited to the natal stream channel. Patterns of regional phylogeographic structure were examined in two related austral orthoclad taxa – Naonella forsythi Boothroyd from New Zealand and Ferringtonia patagonica Sæther and Andersen from southern South America – to provide a comparison with patterns revealed in their close relative E. martini. Both taxa inhabit tectonically active areas of the southern hemisphere that have also experienced several glaciation events throughout the Plio-Pleistocene that are thought to have affected population structure dramatically in many taxa. Four highly divergent lineages estimated to have diverged since the late Miocene were revealed in each taxon, mirroring patterns in E. martini; however, there was no evidence for local geographical endemism, implying substantial range expansion post-diversification. The differences in pattern evident among the three related taxa were suggested to have been influenced by variation in the responses of closed forest habitat to climatic fluctuations during interglacial periods across the three landmasses. Phylogeographic structure in E. martini was resolved at a continental scale by expanding upon the sampling design of Krosch et al (2009) to encompass populations in southeast Queensland, New South Wales and Victoria. Patterns of phylogeographic structure were consistent with expectations and several previously unrecognised lineages were revealed from central- and southern Australia that were geographically endemic to closed forest refugia. Estimated divergence times were congruent with the timing of Plio-Pleistocene rainforest contractions across the east coast of Australia. This suggested that dispersal and gene flow of E. martini among isolated refugia was highly restricted and that this taxon was susceptible to the impacts of habitat change. Broader phylogenetic relationships among taxa considered to be members of this Gondwanan orthoclad group were resolved in order to test expected patterns of evolutionary affinities across the austral continents. The inferred phylogeny and estimated divergence times did not accord with expected patterns based on the geological sequence of break-up of the Gondwanan supercontinent and implied instead several transoceanic dispersal events post-vicariance. Difficulties in appropriate taxonomic sampling and accurate calibration of molecular phylogenies notwithstanding, the sampling regime implemented in the current study has been the most intensive yet performed for austral members of the Orthocladiinae and unsurprisingly has revealed both novel taxa and phylogenetic relationships within and among described genera. Several novel associations between life stages are made here for both described and previously unknown taxa. Investigating evolutionary relationships within and among members of this clade of proposed Gondwanan orthoclad taxa has demonstrated that a complex interaction between historical population fragmentation and dispersal at several levels of evolutionary scale has been important in driving diversification in this group. While interruptions to migration, colonisation and gene flow driven by population fragmentation have clearly contributed to the development and maintenance of much of the diversity present in this group, long-distance dispersal has also played a role in influencing diversification of continental biotas and facilitating gene flow among disjunct populations.

Patterns of site occupancy among boreal stream insects were studied in central Sweden with focus on sparsely distributed species and the role of dispersal and niche limitations.

In the study of dispersal limitation, I found that effects of an extraordinarily harsh winter in small to medium-sized streams were strongest in sites located in small streams and far from lake outlets. Species richness and the total abundance of macroinvertebrates and trout returned to pre-disturbance levels after three years. However, some species showed slow recolonization and the proportion of holoaquatic taxa was still reduced after three years. In a second study, I found a positive correlation between site occupancy in stream caddisflies and morphological traits associated with fast and energy-efficient flight, whereas specialized spring caddisflies showed a negative correlation to these traits compared to stream species. This suggested that streams, but not springs, select for strong dispersal ability in caddisflies. In a survey of springs in central Sweden, hydrogeology was found to be a useful predictor of the occurrence of spring specialists. Two of these, Crunoecia irrorata Curtis and Parachiona picicornis (Pictet), were found exclusively in glaciofluvial springs, characterized by a stable discharge and temperature. Less specialized members of the spring fauna (i.e. species also occurring in streams, ponds or lakes) also occurred in moraine and limestone springs characterized by more unstable conditions.

Niche limitations were studied by contrasting large-scale distributions of closely related rare and common stoneflies. Differences in temperature requirements in the juvenile stages and life cycles suggested that the rare species, Isogenus nubecula Newman, was restricted by a limited tolerance to low stream temperatures, whereas the two common species, Isoperla grammatica (Poda) and Diura nanseni (Kempny), appeared to have a broader tolerance to climatic conditions in the study area. In a second study of niche limitations, macroinvertebrate assemblages in 88 streams in Central Sweden showed a nested distribution pattern. Most species deviating from expected distributions occurred in small streams, indicating competitive exclusion from species-rich sites, predator avoidance, or specialization to unique habitat features of small streams. In the last paper, the longitudinal distribution of filter-feeding caddisflies in a lake-outlet stream demonstrated patterns concordant to feeding specialization.

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Understanding the population dynamic processes is fundamental to access its viability (health). Great part of these processes is closely related to the organism densities in a studied population. These data can reveal how the population is arranged in the environment and, in adverse conditions, it is possible to forecast the occurrence of dispersion/migration. This study aims to investigate some ecological parameters of an Aegla longirostri population, a freshwater anomuran from the southern Brazil: (i) to estimate the population density, (ii) the substrate preference, (iii) the home range and (iv) the possible dispersion patterns. The study site was the first order stream Sanga do Caranguejo, located in the central region of Rio Grande do Sul State, during 2010 and 2011. For population density and dispersion investigation covo traps were used, distributed through the stream, in different times in the year. The study of the substrate preference used PVC gutters covered by mesh and arranged on the stream substrate, with controlled density population; a surber was used for active search in the stream. The home range analysis used radio telemetry techniques. The population size was estimated in 950 individuals in spring and 210 in autumn (estimated according to the Bayesian Method). With respect to the substrate preference, we found that there is an ontogenetic association regarding the choice. The juveniles, in the first development stages, prefer sandy substrates, while adults (males and females) prefer more complex substrates. The estimates of home range of eglids vary between 8,41 to approximately 45,49 linear meters of stream, and these crustaceans showed the local dislocation, once they perform their activities around a specific point in the stream. To finalize, we identified that the juveniles and adults of eglids are active walkers, not being carried by the flow in a passive way as occurs in larvae stage in other crustaceans. Its activities are related to the environment temperature and density of adult males. We believe that the knowledge about the group has increased, however, as it is a complex group, with a rich evolutionary history, much remain to be investigated about these freshwater crustaceans.
A compreensão dos processos de dinâmica populacional é fundamental para se avaliar a viabilidade (saúde) de uma população. Grande parte desses processos estão estreitamente relacionados com a densidade de organismos da população estudada. Estes dados podem revelar como a população está distribuída no ambiente e, em condições de adversidade ambiental, é possível prever a ocorrência de dispersão/migração. Neste estudo, alicerçado nos fatores ecológicos e biológicos do aeglídeo Aegla longirostri foram investigados: (i) estimativa da densidade populacional, (ii) as preferências de substrato, (iii) a área de vida e (iv) os possíveis padrões de dispersão. Este estudo foi conduzido em um riacho de primeira ordem, Sanga dos Caranguejos, que se localiza na região central do Rio Grande do Sul, durante os anos de 2010 e 2011. Nas investigações sobre densidade populacional e dispersão foram utilizados coletores do tipo covo espaçados pelo riacho, em diferentes estações climáticas do ano. A investigação de preferência de substrato foi conduzida com o uso de calhas de PVC cobertas por malha e dispostas no riacho para o experimento em condições de densidade controlada, e com surber, para busca ativa no riacho. A análise de área de vida foi realizada com a utilização da técnica de rádio telemetria. A população em questão foi estimada em 950 indivíduos na primavera e 210 indivíduos no outono (estimativas segundo o Método Bayesiano). Com relação à preferência de substrato, verificamos que há associação ontogenética quanto à escolha. Os juvenis, nos primeiros estágios de desenvolvimento, preferem substratos arenosos, enquanto que adultos (machos e fêmeas) preferem substratos mais complexos. Estimou-se também que a área de vida desses eglídeos varia desde 8,41 metros até, aproximadamente, 45,49 metros lineares de riacho, e que estes crustáceos apresentam comportamento de deslocamento local, já que realizam suas atividades em torno de um ponto específico do riacho. Observou-se ainda que os juvenis eglídeos, assim como os adultos, são caminhadores ativos, não sendo carregados pela correnteza de forma passiva como ocorre nas fases larvais de outros crustáceos. Suas atividades estão relacionadas com a temperatura do ambiente e com a densidade de adultos machos no riacho. Acreditamos que muito se avançou em termos de conhecimento da ecologia do grupo como um todo, e não apenas para a espécie estudada, servindo este estudo de base para estudo futuros sobre dispersão e área de vida principalmente.

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Aquatic birds do interact in many ways with freshwater ecosystems. Birds can be considered the most important dispersers of freshwater algae between water bodies. Moreover, birds also can contribute to nutrient loading in freshwater lakes and reservoirs. In this paper the ecto and endozoochoric dispersal potential of freshwater algae by waterbirds was acessed. The places of study were the Monjolinho reservoir, in São Carlos municipality (SP), and Tropeiros lake, in Piumhi municipality (MG). Also studied was the contribution to nutrient loading by two colonies of Bubulcus ibis, the cattle egret, in two freshwater bodies: Tropeiros lake and Iembó reservoir, locate at Parque Itaipu, São Carlos municipality. By means of culture inoculation with material obtained from washing the body of the birds, it was observed that these species of birds are potential dispersers of phytoplanktonic algae and can carry up to 22 species of algae attached to feathers per individual (ectozoochory). A minor number of species of algae was also observed in cultures inoculated with material derived from faeces of birds, featuring a potential case of endozoochoric transport potential. Regarding the nutrient loading by colony of cattle egrets, was detected a change both in the content of organic matter in the sediment located in areas where the birds sleep as well as greater eutrophication of water in these regions. It was also observed a trend to higher density of biomass in banks of aquatic macrophytes used for night rest, with a consequent increase in the density of organisms associated with aquatic macrophytes. However, no significant differences were observed in the benthic fauna, when comparing the samples of sediment obtained in both points located in the rest areas as in nonrest areas, but it was found that these colonies contribute significantly to the nutrient loading in these systems.
As aves aquáticas interagem de diversas maneiras com os ambientes de água doce. Por um lado, as aves podem ser consideradas como os mais importantes dispersores de algas fitoplancônicas entre os corpos de água doce e, por outro lado, podem contribuir de maneira significativa ao aporte de nutrientes nos ecossitemas aquáticoss. Nesse trabalho foi estudado o potencial de dispersão ecto e endozoocórico de algas fitoplanctônicas por aves aquáticas no reservatório do Monjolinho (município de São Carlos, SP) e na lagoa dos Tropeiros (município de Piumhi, MG), bem como a contribuição de colônias de garças-vaqueira Bubulcus ibis para o aporte alóctone de nutrientes em dois sistemas límnicos: a lagoa dos Tropeiros e o reservatório Iembó, localizado no condomínio Parque Itaipu, no município de São Carlos, SP. Através da inoculação de meios de cultura com material oriundo da lavagem do corpo das aves, foi observado que estas espécies de aves são potenciais dispersoras de algas fitoplanctônicas, podendo transportar até 22 espécies de algas aderidas às penas por indivíduo (ectozoocoria). Um número menor de espécies de algas também foi observado em culturas inoculadas com material oriundo das fezes das aves, caracterizando um potencial de transporte endozoocórico. Em relação ao aporte de nutrientes por colônia de garças-vaqueira, foi verificado uma alteração no teor de matéria orgãnica no sedimento localizado em áreas de poleiro como uma maior eutrofização da água nestas regiões. Foi observada também uma tendência a maior densidade de biomassa vegetal em bancos de macrófitas aquáticas utlizados como poleiro, com um conseqüente aumento na densidade de organismos associados às macrófitas aquáticas. Entretanto, não foram observadas diferenças significativas na fauna bentônica, ao se comparar as amostras de sedimento obtidas em pontos localizados na área de poleiro e área não-poleiro, mas foi constatado que essas colônias contribuem para o estoque de nutrientes nesses sistemas límnicos.

Understanding the mechanisms that regulate local species diversity and community structure is a perennial goal of ecology. Local community structure can be viewed as the result of numerous local and regional processes; these processes act as filters that reduce the regional species pool down to the observed local community. In stream ecosystems, the natural flow regime (including the timing, magnitude, and duration of high and low flow events) is widely recognized as a primary regulator of local diversity and community composition. This is especially true in aridland streams, where low- and zero-flow events can occur frequently and for extended periods of time (months to years). Additionally, wetted habitat patches in arid-land stream networks are often fragmented within and among stream networks. Thus dispersal between isolated aquatic patches may also play a large role in regulating local communities. In my dissertation, I explored the roles that drought, dispersal, and local habitat factors play in structuring arid-land stream communities. I examined the impact of flow permanence and seasonal variation in flow and other abiotic factors on aquatic communities at both fine spatial scales over a long time period (8 years; Chapter 2) and at a broad spatial scale over a shorter time period (1-2 years; Chapter 4). Additionally, I quantified aquatic invertebrate aerial dispersal over moderate spatial scales (��� 0.5 km) by conducting a colonization experiment using artificial stream pools placed along and inland from two arid-land streams (Chapter 4). Finally, I examined the roles of spatial isolation, microhabitat type, and local abiotic and biotic factors in structuring aquatic communities in freshwater oases scattered across one of the most arid regions of North America, the southern Sonoran Desert (Chapter 5). In Chapter 2, I found that severe drought caused an unprecedented drying event in isolated perennial stream pools, and that several additional drying events occurred over the following four years. This transition to intermittent flow caused the extirpation of several large, long-lived species with low dispersal abilities (including the top predator) and drove the local community into an alternative state. In the colonization experiment described in Chapter 3, I found that several arid-land stream invertebrate taxa disperse widely and frequently. The widespread dispersers identified by this experiment included several of the earliest colonist taxa observed following the severe drought described in Chapter 2. Other taxa, though, only dispersed overland after receiving an environmental cue (rainfall) or preferentially dispersed along stream corridors. In Chapter 4, where I examined invertebrate community structure across a large network of well-connected intermittent and perennial reaches, I found low diversity in intermittent reaches, regardless of their connectivity to diverse upstream perennial reaches. These species-poor, intermittent communities were composed of a unique suite of species with lifehistory adaptations that conferred desiccation resistance, including extended egg and larval diapause stages. The short flow duration of intermittent reaches (<100 days) likely precluded upstream perennial taxa from establishing populations in downstream intermittent reaches before drying occurred, while the relative predictability of flow timing (Dec-Apr) likely allowed for a small number of species to develop appropriate life-history traits (e.g., diapause stage, rapid development time) to exploit these temporally-fleeting habitats. In Chapter 5, I found over 220 species of aquatic animals (including ��� 5 undescribed species) in the 19 desert oases that were sampled across the southern Sonoran Desert. Local community composition in these oases was strongly driven by microhabitat type. Additionally, native aquatic species richness and abundance in these oases were significantly reduced by the introduction of tilapia, an exotic fish species. The threats to arid-land streams presented by increased drought severity, anthropogenic water withdrawals, and local habitat degradation (e.g., introduced species, unmanaged recreational use) are grave across the southwestern US and northwestern Mexico. I hope that in addition to furthering our understanding of ecological processes in arid-land streams, this dissertation makes a small contribution towards the efforts to preserve these habitats.
Graduation date: 2013
Access restricted to the OSU Community at author's request from July 18, 2012 - July 18, July 2013

Despite being a highly studied carnivore, the Eurasian otter (Lutra lutra) still offers the opportunity to explore many aspects of its ecology and behaviour that are poorly known or have only been investigated in temperate areas. From April 2007 to October 2010, the OPA research project (Otter Project in Alentejo) was conducted in the south-central Alentejo region of Portugal, in an area of roughly 800 km2. Through the capture and subsequent radio-tracking of 16 wild Lutra lutra individuals (9 males and 7 females) for an average of 139 radio-locations per animal (about 126 days), together with the genotyping of 51 individual otters, the project aimed to provide a set of basic data on the biology and ecology of the species that were missing or limited throughout its extent of occurrence or in the Mediterranean environment. This thesis focus on some of the aspects of the referred project, such as: (1) extent of home ranges (HR) and movement patterns, including their relationships to seasonality and the availability (and its variability) of water resources; (2) genetic spatial structure, dispersal and social interactions; (3) activity rhythms; (4) habitat selection, with particular focus on the modality and frequency of use of reservoirs; (5) testing of a GPS GSM/GPRS telemetry system in riparian habitats and on free-ranging wild otters. Concerning point (1), Network K-function analyses revealed a non-uniform use of home ranges in all monitored individuals of adult size, thus showing fidelity to their annual home range (site fidelity). On average, 49 radio-locations (fixes) (corresponding to approximately 45 days of tracking) were necessary to estimate a stable home range. The estimated average linear extension of home ranges was approximately 16.8 km for females (SE = 2.8) and 38.5 km for males (SE = 2.4), or 22.5 and 92.7 Ha respectively. The maximum extension recorded was 68.1 km (78.6 km including outliers). All individuals had at least one artificial reservoir within their home ranges, representing, on average, 32% of each home range. Several measures of abundance and dispersion of water (which, in turn, also affect the dispersion of aquatic prey) were used in correlation analyses and multiple regression analyses, using Generalized Linear Models (GLM) with the extent of the monitored otters‟ home range as the response variable. The goal was to test the Resource Dispersion Hypothesis (RDH - Macdonald 1983), a hypothesis which predicts, amongst other, the extent of territories in terms of resource dispersion within them. All analyses conducted showed a general influence of abundance and dispersion on otters‟ home range size. However, the response of individuals to changes brought on by the arrival of summer drought was quite diverse. Besides sex and maturity of the animal, it was dependent on the characteristics of the main stream in which it lived and on its space use modality: animals that lived along waterways that have dried up less than the average showed smaller extents of HRs as well as those that consistently used one or a few lentic environments of limited size. Larger extents were usually associated with animals whose HRs were located in areas with high dispersion of water or with individuals which showed a less concentrated use of reservoirs. In general, it appears that the percentage of drought during the dry season determines the minimum HR size (when the otters would tend to enclose within their home ranges patches with a minimum amount of water), while during the wet season – when minimum size is already guaranteed – otters would expand their territories (home ranges) to the surrounding areas, increasing the possibilities of foraging and mating (area-minimizing strategy - Mitchell & Powell 2004, 2007). During a single night (N = 54), otters used on average 3.7 km (SD = 2.9, range: 0 - 14.3) of the annual home range, moving 2 km (SD = 2.8, range: 0 - 22.9) away from the start point of activity (always coinciding with a known resting site) and covering a cumulative distance of 8.2 km (SD = 5.2, range: 0 - 24.2), with a revisiting index ranging from 0 to 4.23 (mean = 2.44, SD = 0.91). Between two fixes of a continuous monitoring session (documented every 15 minutes), the average displacement was 183 m (SD = 355, range 0 - 4271, N = 5609), at an average speed of 712 m/h (SD = 1308; range: 0 - 16325) (N = 5904). All monitored otters (N = 19, including those tagged with GPS harnesses) showed high fidelity to the aquatic habitat, being always located (N = 10286) within a short distance from water (mean = 19 m, SD = 25, range: 0 - 521). Most of the variability observed in movement parameters was caused by interactions between sex, age and season. In particular, adult males were the most mobile category and this was especially true during the wet season, when the greater abundance of water and the return of the hydric connectivity in the previously dried watercourses led to a larger extension in their movements and expansion of home ranges, probably in an attempt to maximize reproductive opportunities. During the wet season movement parameters were generally higher in both sexes, while revisiting rates were higher in the dry season. Correlation analyses performed between movement patterns and variables concerning the dispersion and abundance of water showed that with an increase in the availability of watery sectors the otters increased the amplitude of their movements, reducing their visits to the same portions of their range; on the other side, with a greater fragmentation of the hydrography, indicated by a higher average percentage of dry sites, movements were less extensive and revisits more frequent. Such findings confirm the critical effect that the fragmentation in the availability of the water resource exerts on the biology and behaviour of otters in a Mediterranean environment. Regarding point (2), a mixed approach consisting of genetic techniques and radio-telemetry was used with the following purposes: to verify the existence of a spatial structure in the relationship between individuals of the same population; to investigate the scale of the hypothetical relationship between degree of relatedness and geographic distance; to identify events of dispersal; to verify the hypothesis of a male-biased dispersal in this species; to study the social interactions between monitored individuals. The molecular data refers to DNA extraction from 65 samples of tissue, hair, blood or fresh spraints collected during the project, which led to the genotyping of 51 individuals (28 females and 23 males). These analyses revealed that spatially closer females (N = 286 paired combinations) were more related, while the same cannot be stated for males (N = 224 paired combinations). These patterns are suggestive of male-biased dispersal. Surprisingly, the relationship between geographic distance and relatedness decreased after a threshold of about 30–40 km, suggesting the existence of isolation by distance between individuals of the study population at a fine spatial (and time) scale. The first data on dispersal by this species obtained through radio tracking techniques are presented. These data are the first from a Mediterranean area and are an addition to the only previously reported case on this species (involving a one year old male of a Scottish population marked with radio-active zinc, which dispersed 68 km). Dispersal was detected only in males (N = 4), in a sample of 7 sub-adult individuals monitored; no events of dispersion were documented in either 2 sub-adult females (F6 and F8), nor in one of the males (M4), confirming evidences about male-biased dispersal gathered through molecular analyses. The dispersal distance was on average 20 km (SD = 6), ranging from 10 to 26 km (or 34 ± 9, range: 25 - 47, when expressed as cumulative distance traveled). Possible explanations of the short dispersal distances are discussed. Interestingly, of the 4 sub-adult males of which dispersal was detected, 3 followed the same route and ended up occupying (at different times) almost the same area, although they had potentially available different parts of river catchments and directions. Still regarding the socio-spatial organization of the species, analyses of static and dynamic interactions were performed on individuals with neighbouring or overlapping home ranges. From these analyses, it appears that also in the Mediterranean study area the social organization of the species falls within the classical model of intrasexual territoriality typical of mustelids, with a polygynous breeding system. However, some discrepancies have emerged with regard to what is reported in literature. Contrary to the commonly referred solitary behaviour of the species, monitored otters showed a high degree of overlap in space and time (in some cases even sharing the same diurnal resting sites and even between a male and a female with cubs when the former was known for not being the father). By documenting a large portion of time spent together (not only during matings) by individuals of opposite sex, some flexibility in the social system of this species is highlighted. The evidence gathered confirms the idea that the sociality of a species is complex and variable, and suggests the necessity to undertake further studies on the sociality of the Eurasian otter at the individual level and fine temporal and spatial scale in diverse areas. The otters showed high levels of activity, with 45% of fixes documented as in activity and the remaining 55% at rest and the percentages rosing to 76 and 23, respectively, when considering only night fixes. The activity was, indeed, mainly nocturnal. Among the major determinants of circadian rhythms were foraging strategies (nocturnal hours are believed to present better conditions for catching the two major categories of prey: fish and red swamp crayfish), thermoregulation (to avoid extreme temperatures, both hot and cold), seasonal variability (higher activity during the wet season), age, dispersal events in young males and reproductive status in females. The onset of activity was correlated with sunset time, while the end of activity was less predictable. The hours of greatest activity were concentrated after sunset (from 21:00 to 22:00), in the middle of the night (from 2:00 to 3:00) and before dawn (around 5:00). Multiple regression analyses using generalized linear mixed-effect models (GLMM) showed a combined effect of several weather variables and micro-climatic conditions on nocturnal activity patterns. In particular, among other documented effects, extreme temperatures decrease the probability of finding an otter in activity. The same models, when applied to the width of movement undertaken by the otters, showed the influence of a smaller number of variables. It therefore seems that the decision to be active or not depends much on environmental descriptors, which may in turn regulate the activity rhythms of prey, while the choice to make a substantial move or not is mainly related to intrinsic factors such as sex, age and reproductive requirements. Such choice could also be conditioned by memory/cognitive maps related to resource location, territorial marking needs and interaction with conspecifics. Habitat selection (point 4) was analyzed on a substantial sample of radio-monitored animals through a dual methodological approach, consisting in logistic regression in generalized linear mixed-effect models (GLMM) and the more traditional method of use/availability of Neu et al. (1974). The two methods were applied both on the whole set of fixes and only on the active ones. The final model selected by the GLMM, regarding the probability of an otter visiting a specific sector (100 m) of its home range, seems to indicate that this is influenced by: the distance from the nearest known resting site (with probability decreasing the greater the distance); the type of habitat (water channels were less visited than dams, rivers and ponds), which is in turn dependent on the season (ponds are most visited during the dry season); the presence, during the dry season, of perennial pools; the distance from the site with the highest biomass of the red swamp crayfish (and, as a proxy, also of fish); the distance from the nearest dam (with probability decreasing the greater the distance); the distance from the nearest paved road (there is more chance of a site being visited the further away a road is); and the distance from home range boundaries (the farther from the boundaries, the less likely it is for an otter to visit a site). The probability of otter activity in a particular section within its home range appeared to be influenced by the same factors. However, in this model: the distance from the nearest confluence was also selected (the farther from a confluence site, the lower the probability of selection by an otter during its period of activity); increased activity was associated in decreasing order with ponds, dams and rivers, while in the first model the order was dams, rivers and ponds (it is to be noted that these three habitat types are the most selected in both models). Furthermore, there is a different order in the importance of the variables‟ effects due to slight variations in the estimates of their coefficients and some minor differences in the estimates of the coefficients of the same variables, mainly regarding to the distance from the nearest resting site, which appears greater in the first than in the second model (as expected, since the first also includes fixes during the day, when the otters are on most occasions inactive in their resting sites). All the analyses performed on habitat selection highlight a continuous use of lentic habitats by the otters throughout the year and not just during summer months as previously hypothesized in literature. Reservoirs appear to be selected in particular because of prey abundance (mainly fish, here, on average, more abundant), but, being scarce in terms of cover (therefore shelter availability), they are much less used for resting, for which otters selected streams in the majority of cases. These, however, are also used for foraging, especially for the red swamp crayfish, which is here, on average, more abundant. Ponds are used quite frequently for both activity and rest and they seem to play an important role during cubs‟ raising. The behaviour shown by monitored individuals is consistent with habitat selection already occurring at the landscape scale (second-order selection - Johnson 1980). The selection of streams (in primis) and ponds for resting seems to be due to the high availability of riparian vegetation. Results obtained here therefore highlight the need of a set of habitats for the otter in a Mediterranean context: lentic ones, which serve as main source of water and prey during the extreme summer drought, and lotic ones, richer in riparian vegetation and which therefore provide shelter and conditions for prey resilience in the intermittent isolated pools, confirming what was previously suggested by studies carried out by indirect methods (presence signs‟ surveys). A low-cost GPS GSM-GPRS system (point 5), developed by the Dutch Otterstation Foundation (Netherlands), has been tested in this project for the first time on an otter species (through the use of harnesses). This tool allowed to track animals (N = 6, 711 locations, for a mean period of 9 days and the rate of acquisition of the GPS signal 68.2%) with a high frequency (otherwise impossible based only on man-powered field work) and resulted in a good accuracy level (average error = 8.9 m, SD = 8.5). This experiment was also the first test of a GPS technology in a riparian habitat and on a fresh-water diving animal. The collection of dead animals enabled to expand the sample and to acquire some information on demographic parameters of the studied otter population as well as to perform some morphometric measurements. In particular, the population had a sex ratio of 0.8 males per one female (N = 51), broken down into 39% cubs, 39% adults and 26% sub-adult individuals (N = 40). The estimated average age was 2.2 years (SD = 2.5), with a maximum of 11 years (one female specimen). Death by anthropic causes was noticeable, the major mortality factor being represented by road accidents (62%, N = 24). Mortality events were mainly distributed in the first two months of autumn, after the summer droughts. From the morphometric measurements collected on a sample of 35 animals, the average weight of male individuals was 8.5 kg (SD = 0.9, N = 5) and that of females 6.6 kg (SD = 1.0, N = 10). Average body length was 123.6 cm (SD = 2.6) for males and 111.9 cm (DS = 3.5) for females. Estimates of otter density within individual home ranges of 5 monitored females varied from 0.23 (± 0.05) alle 0.53 (± 0.16) otters per km, depending on whether they are referred to the entire portion of the used water network or only to main rivers respectively. The number of otters captured (N = 47), in particular those equipped with intraperitoneal radio-transmitters (N = 16), together with the long-term average monitoring period per animal (401 days), were higher than those of previous studies of radio tracking of Lutra lutra. This allowed to identify a correct protocol of capture (including the testing of different trapping alarm systems), surgical implant and radio-monitoring of the species, as well as to extend the obtained inferences at a population level. The mixed approach, consisting of radio tracking and molecular techniques, combined with the collection of a fair number of deceased animals in the study area, enabled to gain a wealth of information at the individual level and for a reasonable period of time (about 3 ½ years), covering different aspects of the ecology of a population. The results here provided reveal previously unknown or little known aspects of the eco-ethology of the species, particularly in a Mediterranean environment, such as extents of home-ranges, habitat use and selection, movement and activity patterns, social interactions, dispersal, spatial structure of the relatedness between individuals and density of population. They therefore constitute a source of important information for proper management and conservation of this species in the Portuguese territory (and possibly applicable to other Mediterranean environments). Although the conservation status of otters in Portugal is reassuring, all the evidence collected during this study emphasizes that the Mediterranean populations of this species are subject to significant risks associated with their dependence on water. Different evidence on how the ecology and behaviour of the species are strongly influenced by the climatic characteristics of the Mediterranean environment and the fragmentation and high variability in the availability of the water resource caused by droughts were indeed provided. Such evidence highlight that otters are potentially affected by climate change already in the present and in many aspects of their ecology/behaviour, confirming what was recently suggested for the future distribution of the species through climate simulation models (Cianfrani et al. 2011).