Using Plant Traits To Understand The Impacts Of Plant Invasions On Larval Anurans
Plant detritus is the primary source of energy in freshwater benthic food webs, and the flow of energy from detritus to consumers is largely a function of detritus quality. Theory suggests that invasions by nonnative plants can impact consumers by changing the quality of the detrital pool, but empirical evidence for this is limited. Larval anurans, an abundant constituent of wetlands, may be particularly responsive to shifts in litter quality, as they feed largely on detrital biofilms. I conducted two experiments to evaluate the impacts of nonnative plant litter on larval anurans. For each experiment, I hypothesized that litter quality, including C:N:P, tannin content and lignin content, would determine the number of tadpoles that completed metamorphosis, as well as the productivity, or aggregate mass, of those metamorphs. First, I conducted a field experiment involving four native and five nonnative plant species at five different wetland complexes in central New York. I installed field cages in sites dominated by a single species of each plant and added three tadpole species according to their natural phenology. I monitored cages regularly, collecting and weighing all metamorphosed individuals as they became available. I observed unique interactions between plant and amphibian species, largely driven by the response of larval anurans to plant traits (e.g. sensitivity to plant phenolics). Importantly, my data shows that tadpole performance did not differ in habitats dominated by native or nonnative plants, largely because there are no consistent differences in native and nonnative litter quality. However, my findings do show that plant traits, irrespective of plant origin, do affect tadpole performance. For my second experiment, I raised tadpoles in experimental mesocosms containing an algal slurry and litter from 15 populations of a single nonnative species, Phalaris arundinacea L. (reed canarygrass), that varies widely in litter quality. I observed significant differences in tadpole performance among P. arundinacea populations, and found that litter traits explain a significant portion of the observed variation in tadpole productivity. Increases in P. arundinacea C:P had a negative impact on tadpole performance, while increases in plant phenolics had a positive effect. Overall, my work shows that variation in litter quality, both between and within species, influences secondary productivity in these experimental communities. This suggests that functional traits, irrespective of species origin or identity, can have important consequences for ecosystem function.
dissertation or thesis