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Are we in the midst of the sixth mass extinction? A view from the world of amphibians
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Many scientists argue that we are either entering or in the midst of the sixth great mass extinction. Intense human pressure, both direct and indirect, is having profound effects on natural environ- ments. The amphibians—frogs, salamanders, and caecilians—may be the only major group currently at risk globally. A detailed worldwide assessment and subsequent updates show that one- third or more of the 6,300 species are threatened with extinction. This trend is likely to accelerate because most amphibians occur in the tropics and have small geographic ranges that make them susceptible to extinction. The increasing pressure from habitat destruction and climate change is likely to have major impacts on narrowly adapted and distributed species. We show that salamanders on tropical mountains are particularly at risk. A new and significant threat to amphibians is a virulent, emerging infec- tious disease, chytridiomycosis, which appears to be globally distributed, and its effects may be exacerbated by global warming. This disease, which is caused by a fungal pathogen and implicated in serious declines and extinctions of >200 species of amphibians, poses the greatest threat to biodiversity of any known disease. Our data for frogs in the Sierra Nevada of California show that the fungus is having a devastating impact on native species, already weakened by the effects of pollution and introduced predators. A general message from amphibians is that we may have little time to stave off a potential mass extinction.
chytridiomycosis climate change population declines Batrachochytrium dendrobatidis emerging disease
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Are we in the midst of the sixth mass extinction? A view from the world of amphibians
-
Many scientists argue that we are either entering or in the midst
of the sixth great mass extinction. Intense human pressure, both
direct and indirect, is having profound effects on natural environments.
The amphibians—frogs, salamanders, and caecilians—may
be the only major group currently at risk globally. A detailed
worldwide assessment and subsequent updates show that onethird
or more of the 6,300 species are threatened with extinction.
This trend is likely to accelerate because most amphibians occur in
the tropics and have small geographic ranges that make them
susceptible to extinction. The increasing pressure from habitat
destruction and climate change is likely to have major impacts on
narrowly adapted and distributed species. We show that
salamanders on tropical mountains are particularly at risk. A new
and significant threat to amphibians is a virulent, emerging infectious
disease, chytridiomycosis, which appears to be globally
distributed, and its effects may be exacerbated by global warming.
This disease, which is caused by a fungal pathogen and implicated
in serious declines and extinctions of >200 species of amphibians,
poses the greatest threat to biodiversity of any known disease. Our
data for frogs in the Sierra Nevada of California show that the
fungus is having a devastating impact on native species, already
weakened by the effects of pollution and introduced predators. A
general message from amphibians is that we may have little time
to stave off a potential mass extinction.
11466–11473 PNAS August 12, 2008 vol. 105 suppl. 1
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Area–heterogeneity tradeoff and the diversity of ecological communities
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For more than 50 y ecologists have believed that spatial heterogeneity in habitat conditions promotes species richness by increasing opportunities for niche partitioning. However, a recent stochastic model combining the main elements of niche theory and island biogeography theory suggests that environmental heterogeneity has a general unimodal rather than a positive effect on species richness. This result was explained by an inherent tradeoff between environmental heterogeneity and the amount of suitable area available for individual species: for a given area, as heterogeneity increases, the amount of effective area available for individual species decreases, thereby reducing population sizes and increasing the likelihood of stochastic extinctions. Here we provide a comprehensive evaluation of this hypothesis. First we analyze an extensive database of breeding bird distribution in Catalonia and show that patterns of species richness, species abundance, and extinction rates are consistent with the predictions of the area–heterogeneity tradeoff and its proposed mechanisms. We then perform a metaanalysis of heterogeneity–diversity relationships in 54 published datasets and show that empirical data better fit the unimodal pattern predicted by the area–heterogeneity tradeoff than the positive pattern predicted by classic niche theory. Simulations in which species may have variable niche widths along a continuous environmental gradient are consistent with all empirical findings. The area–heterogeneity tradeoff brings a unique perspective to current theories of species diversity and has important implications for biodiversity conservation.
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Arey 1922.pdf
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Arey 1930s.pdf
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Arey 1932 Glochidial Immunity.pdf
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Arkansas Game and Fish Commission
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The Arkansas Game and Fish Commission’s mission is to conserve and enhance Arkansas’s fish and wildlife and their habitats while promoting sustainable use, public understanding and support.
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Army Corp of Engineers 2003.pdf
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ARSN News: Job Opening - Biologist II - Ecology Option - Alabama Aquatic Biodiversity Center
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The Alabama Department of Personnel is now accepting applications for Biologist II / Ecology Option positions statewide.
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ARSN News: Please Help NC Reel In Interested Fisheries Professionals
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This is YOUR CHANCE come snorkel with the hellbenders!!!
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