Breeding Effort and Hydroperiod Indicate Habitat Quality of Small, Isolated Wetlands for Amphibians Under Climate Extremes

The distribution and function of small, temporarily ponded wetlands such as vernal pools are driven by climate variation, especially precipitation. These wetland ecosystems provide important habitat for amphibians, whose breeding effort (egg deposition) is often used to characterize pool habitat quality. However, whether breeding effort consistently predicts larval survival, juvenile production, and overall reproductive output—key indicators of habitat quality for amphibians in a varying environment—remains unclear. We assessed the occurrence of spotted salamander (Ambystoma maculatum) and wood frog (Lithobates sylvaticus) larvae in 71 vernal pools in New York, USA during the spring and summer of 2016 and 2017—the fifth driest and third wettest years in regional history, respectively—to better understand the relationship between breeding effort and metamorph production under environmental extremes. Breeding effort was an important predictor of whether late-stage larvae occurred in pools for both species. However, occurrence of late-stage larvae was substantially lower for both species during 2016, i.e., the drought year, when pools dried rapidly. These outcomes suggest that, in the face of an increasingly variable climate, prioritizing clusters of pools that encompass a range of hydroperiods and include high-productivity pools would help maintain populations of vernal-pool dependent amphibians.