Using Functional Traits To Understand How Changes In Plant Species Composition Will Affect Larval Amphibians

Abstract

The vast majority of plant material becomes detritus, and in its 'afterlife' this plant litter is a critical resource for many aquatic organisms. I conducted four experiments to improve our understanding of how changes in plant commu nities may affect aquatic organisms. In each experiment, I used larval anurans as a focal organism, since many studies show that larval anurans are sensitive to changes in litter inputs. All experiments were conducted in outdoor mesocosms containing plan t litter, microbes, algae, and tadpoles. In all cases, I predicted that as litter quality or quantity increased, tadpole performance - measured as survivorship, development rate, and body size would improve. In one experiment, I varied litter quantity a nd observed that tadpole development and size increased with litter quantity. In a second experiment, I examined how the presence of a predator affected tadpole performance. I predicted that predators would decrease tadpole performance, but that these ne gative effects would attenuate as litter quality increased. I found that tadpole survival and mass increased with litter quality but saw no apparent effects of predators. In a third experiment I collected soil from six different sites and created inocula for outdoor mesocosms to see whether tadpole performance would vary among inocula. Tadpoles developed faster and achieved greater body size when raised with higher quality litter, but I did not detect differences in tadpole performance among soil inocula. In a fourth experiment, I used litter from six plant species to create nine unique mixtures of three species each. I predicted that as plant functional diversity increased, tadpole performance would improve. I also predicted that tadpole performance wo uld improve as community-weighted mean (CWM) nitrogen and phosphorus increased and CWM lignin and phenolics decreased. I did not observe any differences in tadpole performance based on functional diversity, but found that tadpole performance improved as CWM nitrogen increased and CWM phenolics decreased. My work shows that plant litter quality is a consistent predictor of larval anuran performance, even when there are multiple plant species, predators, or variation in soil biota communities.