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WEAKLY SYNCHRYRONIZED SUBPOPULATION DYNAMICS IN WISCONSIN FROGS AND TOADS
Citation:
Trenham, P. C. WEAKLY SYNCHRYRONIZED SUBPOPULATION DYNAMICS IN WISCONSIN FROGS AND TOADS. Presented at 86th Annual Meeting of the Ecological Society of America, Madison, WI, August 5-10, 2001.
Description:
Spatial synchrony in population dynamics is a topic of increasing interest in basic and applied ecology. We used data from 18 years of frog and toad calling surveys conducted throughout Wisconsin to determine the level of intraspecific synchrony among survey sites, and the relationship between synchrony and intersite distance. Cross-correlations between anuran calling data and rainfall data from nearby weather stations were used to determine if population fluctuations were associated with precipitation. For sites separated by less than 10 km, six of eight anuran species were weakly but significantly synchronized, and detectable synchrony extended to sites separated by 75 - 100 km for one species (Bufo americanus). In contrast annual rainfall totals were strongly synchronized even among sites separated by 75 - 100 km. Relative to rainfall, call intensities were most strongly correlated with rainfall totals one to four years earlier, rather than with rainfall concurrent with frog surveys, supporting the assumption that call indices reflect changing population densities. We suggest that the relatively limited dispersal abilities of anurans and often divergent characteristics of nearby wetland habitats serve to decouple population dynamics. Given the weak synchrony observed here, extrapolation of regional dynamics from fewer localized surveys cannot be considered an option for monitoring programs, and regionally synchronized extinctions are unlikely to reduce metapopulation persistence times in these species.