Добірка наукової літератури з теми "Endemics-area relationship"

Patterns in species density and richness per altitudinal interval have been found when sampling across plant-community boundaries, including in the largest contiguous alpine area in Australia. To see if similar patterns occur within a single community, vascular-plant composition was systematically sampled with replicate nested quadrats of increasing size (0.01, 0.06, 0.25, 1.00, 4.00, 25.00, 49.00 and 100-m2 size) sampled from ~1850-m to 2100-m altitude in tall alpine herbfield, Australia. The only significant relationships with altitude were quadratic relationships for the density of herb and graminoid species, with peak density at middle altitudes and a linear decline in total species richness with altitude for 0.06-m2 quadrats. The composition of 100-m2 quadrats was unrelated to altitude when tested with analysis of similarity for total composition, whereas the relationship was significant for growth-forms and the origin (local endemics, Australia endemics and weeds) of species. Location data from this, and 11 other studies were used to compare the species richness of more of the flora (183 species) in 50-m altitudinal bands. There were significant quadratic relationships for total species richness and the number of herb and shrub species, with a peak in richness at ~2000 m. Therefore, altitude does affect species richness overall in this alpine region, although it has only a weak effect on species density within the most common plant community.

Biotectonics is an approach to historical biogeography based on the analysis of independently derived biological and tectonic data, which we demonstrate using the island of Sulawesi as an example. We describe the tectonic development of Sulawesi and discuss the relationship between tectonic models and phylogenetic hypotheses. We outline the problem of interpreting areagrams based on single phylogenies and stress the importance of combining all available data into a general areagram. We analysed the distributions of Sulawesi area of endemism endemics (AEEs) using 30 published phylogenies, which were converted into paralogy-free taxon-area cladograms using the programme LisBeth (Zaragüeta-Bagalis et al. 2012) from which Adam’s consensus trees were constructed using PAUP (Swofford 2002). The results of our analyses show that the relationship between the areas of endemism is congruent with the terrane history of the island. A further 79 phylogenies of Sulawesi species with extralimital distributions were analysed to determine area relationships of Sulawesi within the broader Indo-Pacific region. We demonstrate the utility of data partitioning when dealing with areas that are geologically and biologically composite by showing that analysing Asian and Australasian elements of the Sulawesi biota separately produced general areagrams that avoid artifice and are interpretable in the light of current tectonic models.

The limbless, primarily soil-dwelling and tropical caecilian amphibians (Gymnophiona) comprise the least known order of tetrapods. On the basis of unprecedented extensive fieldwork, we report the discovery of a previously overlooked, ancient lineage and radiation of caecilians from threatened habitats in the underexplored states of northeast India. Molecular phylogenetic analyses of mitogenomic and nuclear DNA sequences, and comparative cranial anatomy indicate an unexpected sister-group relationship with the exclusively African family Herpelidae. Relaxed molecular clock analyses indicate that these lineages diverged in the Early Cretaceous, about 140 Ma. The discovery adds a major branch to the amphibian tree of life and sheds light on both the evolution and biogeography of caecilians and the biotic history of northeast India—an area generally interpreted as a gateway between biodiversity hotspots rather than a distinct biogeographic unit with its own ancient endemics. Because of its distinctive morphology, inferred age and phylogenetic relationships, we recognize the newly discovered caecilian radiation as a new family of modern amphibians.

The major centres of local endemism and richness at the species level and below in Spyridium Fenzl are located on the southern coast of Western Australia and in south-eastern South Australia. There are only a few Spyridium taxa with ranges that transgress the boundaries of the following four regions: south- western Western Australia; south-eastern South Australia and western Victoria; eastern Victoria, New South Wales and southern Queensland; Tasmania. Synthetic climatic variables were generated for all recorded populations of Spyridium taxa. Variabilities in these were related to the maximum geographic ranges of taxa in Australia as a whole, and within the regions, in order to test the hypothesis that narrow endemism is explained by climatic restriction since the last glacial. In Australia as a whole, local endemics are both narrowly and widely distributed climatically, as are more widespread Spyridiumtaxa, and there were no significant relationships between the climatic and geographic ranges of taxa confined to the Australian mainland regions. However, Tasmanian taxa exhibited a strong positive relationship. Restriction of range as a result of climate change is an unlikely explanation for local endemism in Spyridium in mainland Australia, where topographic and climatic gradients are generally subdued, and which apparently experienced less severe climatic oscillations during the Quaternary. However, this hypothesis cannot be rejected for Tasmania, which experienced more extreme Quaternary climatic fluctuations than the present-day areas of mediterranean climate, and hence more severe fluctuations in the area and location of climatically suitable habitats.

Wetlands are among the most threatened habitats on Earth. They are essential components of functional landscapes, providing habitat for native flora and fauna as well as supporting critical ecosystem services. Loss of wetland biodiversity threatens these values. There is an urgent need to understand patterns of wetland biodiversity, the processes creating these and the risk of species loss to plan effective intervention. Species-area relationships have a successful, although controversial, history of quantifying the risk of extinction in terrestrial biomes, and can provide rapid estimates of extinction risk at a range of scales without the need for extensive datasets. Prior to my research, applications of species-area relationships in extinction risk were limited to island archipelagos and formerly continuous terrestrial habitats that had become fragmented. Naturally occurring, discrete habitat types—such as wetlands—have been ignored. I address this gap, demonstrating that area-based methods can, with some modification, be successfully applied to predict extinction risk in wetland communities. Before considering extinction risk I analysed patterns of wetland plant diversity and occupancy and how competing community-assembly processes produce more or less unique combinations of species among wetlands. I showed that much of the plant community diversity in seasonal wetlands in South Australia is driven by rare terrestrial species of wetland fringes, which assemble from a much larger available species pool. The distribution of these rare species was not correlated with total species richness or wetland size, suggesting that changes in the number or total area of wetlands could result in different extinction dynamics, depending on how they affected endemic species. I therefore compared risks associated with loss of complete wetlands (patch loss), with loss of the equivalent wetland area while maintaining the total number of wetlands. To implement the latter scenario, I developed a novel approach consisting of three steps: (i) a generalized empirical endemics-area relationship to predict the number of species lost within each wetland as a function of a reduction in wetland area; (ii) I selected the identities of the predicted number of species lost at each wetland probabilistically; (iii) I compred the number of wetlands from which each species was lost with its regional occupancy, and I considered any species predicted to be lost from all known sites as extinct. I then repeated steps (ii) and (iii) many times to obtain a distribution of regional-scale species loss for a given loss of area in each wetland. Step (ii) allowed for different scenarios to be tested by adjusting the sampling probability for each species. I found that a higher extinction risk was associated with the loss of complete wetlands than the equivalent area loss shared among all wetlands. Moreover, for a given area loss, small wetlands had a much higher risk of species loss due to the distribution of endemic species. The approach I developed could be readily applied to any discrete habitat type, providing predictions of risk for a range of ecosystems that have received little attention.
Thesis (M.Phil.) (Research by publication) -- University of Adelaide, School of Biological Sciences, 2016.

<em>Abstract.</em>—We quantified the relationships among urban land cover, fishes, and habitat quality to determine how fish assemblages respond to urbanization and if a habitat index can be used as an indirect measure of urban effects on stream ecosystems. We sampled 30 wadeable streams along an urban gradient (5–37% urban land cover) in the Etowah River basin, Georgia. Fish assemblages, sampled by electrofishing standardized stream reaches, were assessed using species richness, density, and species composition metrics. Habitat quality was scored using the Rapid Habitat Assessment Protocol (RHAP) of the U.S. Environmental Protection Agency. Urban land cover (including total, high-, and low-density urban) was estimated for the drainage basin above each reach. A previous study of these sites indicated that stream slope and basin area were strongly related to local variation in assemblage structure. We used multiple linear regression (MLR) analysis to account for this variation and isolate the urban effect on fishes. The MLR models indicated that urbanization lowered species richness and density and led to predictable changes in species composition. Darters and sculpin, cyprinids, and endemics declined along the urban gradient whereas centrarchids persisted and became the dominant group. The RHAP was not a suitable indicator of urban effects because RHAP-urban relationships were confounded by an overriding influence of stream slope on RHAP scores, and urban-related changes in fish assemblage structure preceded gross changes in stream habitat quality. Regression analysis indicated that urban effects on fishes accrue rapidly (<10 years) and are detectable at low levels (~5–10% urbanization). We predict that the decline of endemics and other species will continue and centrarchid-dominated streams will become more common as development proceeds within the Etowah basin.