Wetland Hydrology, Not Altered Phenology, Challenges Reticulated Flatwoods Salamander (Ambystoma bishopi) Management Under Future Climate Change

Shifts in phenology have been one of the most frequently documented effects of climate change across a wide variety of taxonomic groups. These shifts can alter both species and ecosystem level processes and, for species of conservation concern, may impact the effectiveness of ongoing management programs. Here, we used ten breeding seasons (2010–2020) of drift fence data to quantify the breeding phenology of the imperiled Reticulated Flatwoods Salamander (Ambystoma bishopi) at two breeding wetlands in Florida. We then used downscaled climate projections from three Global Circulation Models (GCMs; Hadley Centre Global Environment Model 2 Earth Systems, Hadley Centre Global Environment Model 2 Carbon Cycle, and the Community Climate System model version 4) each with two emission scenarios to forecast how flatwoods salamander breeding phenology may change from 2030–2099. We combined these forecasts with an existing hydrologic model that was built using the same climate data to examine how wetland hydrology and phenology may interact to impact salamander recruitment in future years. We found that large movements (≥ 5 individuals) of adult salamanders moving into breeding wetlands were tightly linked to precipitation events with minimum temperatures above freezing, while juvenile emigration was less strongly tied to precipitation and occurred on more days than adult immigration. Under all six GCM-emission scenario combinations, only one scenario suggested that there would be fewer immigration opportunities by the year 2099, and two scenarios (both high emission) indicated that the timing of immigration may shift to later in the fall breeding period. All projections predicted that only a few years will have an ideal intersection of phenology and hydrology for flatwoods salamander reproduction but that many years would have marginal conditions where recruitment may still be possible. Because the frequency of successful breeding years affects population viability in flatwoods salamanders, ongoing management programs must ensure that populations are reproducing frequently enough to remain viable. Overall, our results indicate that altered wetland hydrology (e.g., shorter hydroperiods during the breeding season) and other effects of climate change (e.g., sea level rise) are more likely to contribute to flatwoods salamander declines over the next several decades than phenological shifts.