Interaction of an Introduced Predator with Future Effects of Climate Change in the Recruitment Dynamics of the Imperiled Sierra Nevada Yellow-legged Frog (Rana sierrae)

Abstract

Between-year variation in snowpack (from 20 to 200% of average) and summer rainfall cause large fluctuations in volume of small lakes in the higher elevation (> 3000 m) Sierra Nevada, which are important habitat for the imperiled Sierra Nevada Yellow-legged Frog, Rana sierrae. Climate change (global warming) is predicted to increase these fluctuations, potentially leading to more frequent summer lake drying of shallow, fishless ponds where most R. sierrae breeding and larval development (requiring ≥ 3 years) occurs today. This study explored the interaction between water availability and the abundance and recruitment of R. sierrae in Dusy Basin, Kings Canyon National Park, California, USA. We mapped the Dusy Basin lakes with GPS, calculated water volumes in a low-snowpack and a high snowpack year (2002, 2003), and counted R. sierrae. The lakes that dried up in 2002 were repopulated by adults in 2003, without any recruitment of metamorphosed frogs from previous year’s tadpoles. The lakes that retained water, even with notable volume decreases (-60%), showed tadpole-to-subadult recruitment in the following year (2003). Similar results are obtained using data for years 1997-2006: significantly greater abundance of metamorphs in permanently wet lakes than in lakes that had dried even once during the 10 years. Similarly, those lakes that had retained water during any two preceding years had significantly more metamorphs than lakes that had dried up during that period. Our results suggest that any increase in drying of small ponds will severely reduce frog recruitment. Combined with the invasive fish that prevent frog breeding in larger lakes, lake drying may cause extinction of local frog populations.

Citation

Lacan, K.R. Matthews, and K.V. Feldman. 2008. Interaction of an Introduced Predator with Future Effects of Climate Change in the Recruitment Dynamics of the Imperiled Sierra Nevada Yellow-legged Frog (Rana sierrae). Herpetological Conservation and Biology 3(2):211-223.