Tuesday, August 4, 2009

PS 22-24: Cross-generational effects of amphibian larvae removal: Evidence for an ecological feedback

Joseph R. Mihaljevic, Kevin G. Smith, and Jonathan M. Chase. Washington University in St. Louis

Background/Question/Methods

A poorly-understood threat of the global decline of amphibian populations is the potential for feedbacks of population declines across generations. The importance of tadpoles as consumers in aquatic food chains suggests that tadpole absence in one generation may alter community composition sufficiently to affect future tadpole recruitment and success, resulting in an ecological feedback. In this study, we used an established mesocosm experiment to investigate the breeding site preference and larval success of Gray Treefrogs in response to the prior year’s presence (control) or absence (removal) of tadpoles. Each day we counted new egg clutches to quantify breeding events and counted, measured, and weighed emergent metamorphs. 
Results/Conclusions

The previous year’s tadpole presence or absence had no significant effects on adult breeding site preference, body length, or mass of the next generation’s tadpoles. However, we saw a trend of greater tadpole success in the control treatment, which had over twice the larval success compared to the removal treatment. This difference has clear biological implications since the number of emerging juveniles can affect local terrestrial amphibian population dynamics. Thus, the community-level consequences of tadpole absence may negatively affect future generations, potentially exacerbating the consequences of amphibian population declines via an ecological feedback.