No apparent effects of soil inoculum on green frog (Lithobates clamitans Latreille) tadpole performance

Abstract

Invasions by nonnative plant species are transforming plant communities across the globe. An important challenge for ecologists is to understand how animals will respond to these changes. One way that plant invasions could affect aquatic animals is by changing the rate at which soil communities decompose litter, which could alter the flow of energy and nutrients from plant litter to aquatic communities. In this study, we measured larval amphibian responses to soil conditioned by either introduced or native genotypes of Phragmites australis L. (common reed) in northeastern North America. We collected soil from adjacent stands of introduced and native P. australis at three sites in central New York and inoculated outdoor aquatic mesocosms with soil extracts. Mesocosms contained six Lithobates clamitans Latreille (green frog) tadpoles and either low- or high-quality native P. australis americanus litter. We found that litter decomposition differed based on soil inoculum, and we observed a significant interaction between litter quality and soil inoculum; higher-quality litter tended to decompose faster when exposed to inocula from introduced P. australis, while lower-quality litter tended to decompose faster when exposed to inocula from native P. australis americanus. Tadpoles raised with high-quality litter developed faster and achieved greater body size, but soil inocula had no apparent effect on tadpoles. Our results suggest that plant invasions may alter microbial communities, causing subtle changes in litter decomposition rates, but these changes do not appear strong enough to influence larvae of a widespread amphibian.