Murray State Theses and Dissertations


Predation plays a crucial role in shaping community structure and can initiate trophic cascades that can alter abundances across adjacent trophic levels. Recent research has suggested that variation among individual predators may have stronger effects on ecological dynamics than previously appreciated. Intraspecific variation within predators could lead to differential levels of top-down control with implications for trophic cascade strength. In this experiment, we manipulated the body size variation of predatory mole salamanders (Ambystoma talpoideum) within experimental mesocosms and monitored a suite of abiotic and biotic response variables. We predicted that predator populations with increased body size variation would have limited top-down control due to weaker interactions with a greater number of prey species. Conversely, we predicted that populations with similarly sized predators would have strong control over fewer prey species. Salamander presence affected nearly every biotic parameter measured, suppressing some populations (e.g. invertebrate predators) and facilitating others (e.g. invertebrate collectors), triggering multiple trophic cascades. A few invertebrate taxa responded to variation in predator body size and in nearly all of these instances, taxa responded more strongly to treatments with increased body size variation than in treatments with similarly-sized predators. Predator size variation may promote individual dietary specialization by differently sized predators, resulting in strong control of focal prey. These results demonstrate that predators have pervasive effects on all trophic levels of a community regardless of size structure, and that when size structure has an effect on abundances of particular taxa, increased body size variation can lead to stronger top-down control.

Year manuscript completed


Year degree awarded


Author's Keywords

trophic cascades, predation, intraspecific variation, body size variation, Ambystoma talpoideum

Thesis Advisor

Howard H Whiteman

Committee Member

Cy Mott

Committee Member

Michael Flinn

Committee Member

Christopher Mecklin

Document Type