The effects of novel leaf litter deposition on competitive, predator–prey and host–parasite interactions of American toad larvae

Wetland plant communities are changing rapidly due to a wide range of
human activities. The deposition of leaf litter from novel plant
communities can alter both the chemical and physical habitat of aquatic
ecosystems. Lesser understood are the ecological consequences of novel
leaf litter inputs in aquatic communities. Towards this goal, we used two
plant invasion scenarios (comparing native black huckleberry to exotic
autumn olive and native swamp loosestrife to exotic purple loosestrife) to
simulate a shift in wetland plant communities. In this study, we
investigated the effects of novel leaf litter leachates on three aquatic
ecological interactions: intraspecific competition, predation, and
parasitism. We examined how leaf litter leachates influence the
interactions of American toad larvae (Anaxyrus americanus) with their
conspecifics, a dragonfly predator (Anax spp.) and a trematode parasite
(Echinostomatidae). We found that leaf litter type influenced competitive
interactions only for the huckleberry versus autumn olive comparison. We
did not detect any effects of leaf litter type on predator-prey
interactions. Finally, litter type strongly influenced host-parasite
interactions for both leaf litter comparisons, altering host
susceptibility, parasite survival and net infection rates. These results
highlight the breadth of potential ecological repercussions of shifting
wetland plant communities for native ecosystems.