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David M. Green
Professor and Director
Telephone: (514) 398-4086 ext. 4088
Evolutionary Genetics and Conservation Biology of Amphibians
I employ evidence from biochemical and molecular genetic variation in frogs and toads to decipher the relationships of species, the structure of populations, and mechanisms of evolutionary change.
Compared to the attention given to the factors that influence population size and persistence, little has been paid to what determines the extent of a species' range. Yet population declines and species endangerment are only a facet of the greater issue of species range expansion and contraction. My research centres on species ranges and boundaries and thus looks beyond traditional population-level approaches to understanding biodiversity origins and maintenance. Range edge populations are reasoned to be genetically depauperate and isolated, and therefore prone to local extinction. These same parameters govern a species' endangerment and risk of decline thus a solid basis for assessing endangerment will benefit from comprehension of the range edge. The range edge is also predicted to be limited by gene flow from the range centre constraining local adaptation.
Amphibian species are demonstrably in global decline and they often have complex local or regional population dynamics. They are excellent subjects for ecology, conservation biology, and molecular genetics as they exhibit a range of life history strategies and breed in discrete sites such as ponds where they are easily sampled. They are not highly mobile and have characteristic patterns of dispersal. I am analyzing ecological data and genetic variation to estimate population structure and gene flow, as a measure of dispersal, in common and endangered species of frogs, toads and salamanders in Canada and in the tropics.
My continuing study of Fowler's toads (Bufo fowleri) at Long Point, Ontario has now run continuously for over two decades. It has charted how the number of animals has fluctuated, how radical year-to-year changes in age structure depend upon recruitment of juveniles and winter survival, and how far and fast both adults and juveniles disperse. Through this work, Fowler's toad is the one of the most thoroughly studied of amphibians.
By seeking to understanding range edge populations more fully, my research program aims towards understanding the biology of extinctions, the persistence of populations, and the conservation of species.