Date of Award

January 2019

Degree Type

Open Access Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

First Advisor

Cy L. Mott

Second Advisor

Stephen C. Richter

Third Advisor

Amy Braccia

Abstract

Biodiversity is often emphasized at the species level where each species is assigned a mean functional trait value. However, populations within a species, and individuals within a population, often exhibit considerable intraspecific functional variation. Therefore, instead of focusing on species’ mean trait values, we must incorporate intraspecific variation when considering species’ ecological roles and conservation values. The primary objective of this study was to determine the effects of variation in body size (a functional trait in many aquatic taxa) in an apex predator on ecosystem functioning. We sought to characterize trophic cascades initiated by larval populations of Ambystoma jeffersonianum that varied in size structure based on diversity of maternal lines (i.e., sibship diversity) by quantifying the effect on larval salamanders, benthic macroinvertebrates, zooplankton, phytoplankton, and periphyton, as well as leaf-litter decomposition rates and release of soluble nutrients in cattle tank mesocosms. Although sibship diversity did not lead to populations of variable body size, it was positively related to larval density and survival to metamorphosis in A. jeffersonianum. Sibship diversity did not affect growth rates or dates of metamorphosis for A. jeffersonianum, nor did it have any significant effects on invertebrate communities and ecosystem function. This research emphasizes the importance of considering the effect of sibship diversity on predator density for intraspecific variation and the subsequent long-term effects on ecosystem function.

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