Effects of Leaf Litter Species on Cope's Gray Treefrog Oviposition Site Selection

Leaf litter is an important input to a variety of freshwater ecosystems. The species of leaf litter affects water chemistry, ecosystem processes, and the survival and growth of aquatic organisms. Given the potential fitness consequences, it is likely that aquatic organisms have preferences for aquatic habitats with particular species of leaf litter input. To investigate this, we placed shallow experimental pools at a field-forest edge in northern Louisiana, USA as potential sites for Cope's Gray Treefrog (Hyla chrysoscelis) oviposition with leaf litter from one of 14 different tree species in each pool. Tree species included 13 native trees and one invasive species, Bradford Pear (Pyrus calleryana). We measured the concentrations of tannins and 12 elements in leaf tissue, along with water quality and water depth in the pools. We used an information-theoretic approach and created different models to determine what variables best predict the number of treefrog eggs laid in each pool and thus may serve as a cue for female treefrogs during oviposition site selection. We found that tree species treatment was by far the best predictor of the number of eggs Cope's Gray Treefrogs laid in the pools. Treefrogs laid more eggs in pools with Post Oak and Sweetgum leaves and fewer eggs in pools with Southern Red Oak and Southern Magnolia leaves. It is unclear how female treefrogs are able to differentiate among these tree species or what cue they are using to make their choices. Our results highlight the importance of tree species to aquatic community assembly.