| dc.description.abstract | The preservation of biodiversity has become a fundamental ecological
goal in recent years. If we wish to prevent or reverse worldwide amphibian
declines it is imperative that we understand patterns of abundance and
distribution and the causal factors. Virtually every aspect of the amphibian life
cycle depends on water, and therefore wetland hydroperiod plays an important
part in amphibian species richness and the distribution of individual species,
particulary since two major perceived stresses on amphibians are desiccation
stress and predation by fish. I used repeated surveys (breeding call and visual
surveys) to investigate amphibian species richness and incidence of 93 wetlands
(31 each of permanent, semi-permanent and temporary) in Northwestern Ontario
in relation to hydroperiod and a number of other wetland characteristics.
Amphibian species richness and incidence differed among hydroperiod
categories. Species richness peaked in semi-permanent wetlands and was
higher in permanent than temporary wetlands, despite presence of predatory
fish. Some species, even those considered ‘temporary’ occurred equally among
all wetland types while others were more likely to be found in one or two
hydroperiod categories. Species that I found to be rare in the study region may
be affected negatively by the amount of roads on the landscape. Salamanders
appeared very susceptible to alterations of the landscape. Percent forest cover
does not appear to be a factor in determining patterns of species richness or
distribution, as it is in other areas. There may be a minimum 'threshold' of forest
cover, below which amphibian species decline rapidly, that has not yet been reached in my study region. Permanent bodies of water offer suitable amphibian
habitat, despite potential predation by fish. Amphibian species richness was
equal among lakes with or without predatory fish present. The availability of
refuge habitat significantly increased amphibian species richness in lakes. I
suggest that lakes should not be overlooked as amphibian habitat and as
conservation areas. Lakes are suitable habitat for wetland-dependent organisms
like amphibians, and being permanent, are available for use even during times of
drought when other less permanent wetlands are not. | |
