Regional dynamics of wetland-breeding frogs and toads: Turnover and synchrony

We used data from a statewide frog monitoring network to investigate population turnover and synchrony in eight wetland-breeding species. We found that subpopulations at many sites turn over frequently, with breeding choruses absent or undetectable in most years. Frequencies of detection across sites were significantly associated with the density of wetland patches (all species) and the areal extent of several terrestrial land cover categories (seven species) within 1 km. Intraspecific population fluctuations were statistically synchronized between survey sites separated by up to 50-100 km, but synchrony was not strong. Anuran abundances were significantly correlated with rainfall 1-4 years earlier, indicating that rainfall influences population fluctuations. However, population synchrony was much weaker than rainfall synchrony. Managers attempting to maintain amphibian populations regionally should focus on maintaining landscapes with high densities of wetlands and sufficient upland habitat resources. The dynamic nature of amphibian populations at individual wetlands is well known, and our results suggest that species distributions at the landscape level are similarly dynamic.