Monday, August 6, 2007

PS 2-24: Spatial and temporal patterns of breeding site selection in ambystomatid salamanders

Craig D. Snyder1, James T. Julian2, and John A. Young1. (1) USGS Leetown Science Center, (2) Pennsylvania State University

We used Classification and Regression Tree analyses to explore spatial and temporal patterns of breeding site selection in three species of ambystomatid salamander in 133 natural ponds or wetlands in the Delaware Water Gap National Recreation Area.  Spatial patterns of site selection in two species (Ambystoma maculatum and A. opacum) were strongly related to interactions among several important habitat gradients including hydroperiod, the amount of roads near breeding ponds, and the pH of the pond or wetland.  In contrast, habitat predictors were much weaker for A. jeffersonianum.  Instead, strong associations between longitude and especially latitude and breeding site use in A. jeffersonianum was observed suggesting that the larger “metapopulation” may be either expanding or contracting in size, and habitat was only secondarily important.  The three species differed in terms of population trends over time.  Over the 3-yr period between 2000 and 2002, the proportion of available breeding habitat used increased for A. maculatum, decreased for A. jeffersonianum and remained essentially unchanged for A. opacum, whereas turnover (i.e., change in occupancy status at a site between years) was low for A maculatum and A. jeffersonianum, but relatively high for A. opacum. Our data suggest variation in temporal patterns were likely due to species-specific responses to rainfall patterns that were dictated by innate differences in reproductive behavior.

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