Holy Moley! Using mole salamanders (Ambystoma talpoideum) to understand the impacts of body size variation of top predators on trophic cascades

Trophic cascades are ubiquitous in natural systems and have widespread implications for natural resource management, conservation biology, and agriculture. Classic understanding of ecosystem dynamics, including trophic cascades, rarely incorporates variation at a finer scale than species. Investigating the influences of interspecific variation can further our understanding of these complex ecological interactions. In this project, we use mole salamanders (Ambystoma talpoideum) to explore the impacts of body size variation in a top predator population on an aquatic ecosystem. We hypothesized that populations of mole salamanders with smallest variation in body sizes would exhibit strongest trophic cascades. Trophic cascade strength would weaken as body size variation increased, due to cannibalism and more diffuse predation pressure. To test these questions, we constructed 54 identical artificial pond ecosystems which were populated with one of three salamander size-structure treatments. We monitored changes in the ecosystems through a suite of abiotic and biotic parameters over a period of six months. Preliminary results show that there may be an effect of salamander presence on primary production, but not on zooplankton populations. Further analyses on tadpole and macroinvertebrate community populations are currently in progress to further understand the linkages within this food web and confirm the presence of a trophic cascade