Population biology, genetics, and sexual selection in wild ambystomatid salamanders

Rod N Williams, Purdue University

Abstract

Ambystomatid salamanders have long served as models in studies investigating the factors influencing sexual selection due, in part, to their diverse mating behaviors and breeding strategies. However, our current knowledge regarding rates of multiple mating, individual reproductive success, and inbreeding depression is very sparse or lacking altogether in most species. Thus, in this dissertation I used molecular genetic analyses to address these cryptic aspects of salamander natural history. Chapter one focuses on the complex relationships among breeding chronology, environmental conditions, and body size in Small-mouthed (Ambystoma texanum) and Eastern Tiger Salamanders (A. tigrinum tigrinum). I found that both species immigrated over a short period of time and displayed no clear pattern as to whether males or females typically arrived first at breeding ponds. My analyses revealed that there was no size-ordered immigration or emigration for either species examined; migration events were triggered by temperature and precipitation. Subsequently, I attempted to study the effects of body size on relative reproductive success and sexual selection in a breeding congregation of adult tiger salamanders using molecular parentage analyses. My results indicate that body size was not correlated with mating or reproductive success in either sex. Bateman gradients were significant and nearly identical in both sexes, suggesting that reproductive success was enhanced by increased mating success and that the intensity of sexual selection was roughly equal between sexes. The remainder of my dissertation focused on whether inbreeding can be considered a causal factor in salamander malformations. I tested whether malformed tiger salamanders were more inbred and/or had less genetic diversity than normal salamanders. I found that genetic diversity was high across markers, across life stages, and in both malformed and normal individuals. Genetic analyses of normal versus malformed individuals revealed no significant difference in measures of inbreeding, allele frequencies, mean individual heterozygosity, or mean internal relatedness. Collectively, this research describes several aspects of small-mouthed and tiger salamander migration patterns, provides a wealth of novel natural history data relating to tiger salamander reproductive biology, and provides new empirical evidence to address concepts central to sexual selection theory.

Degree

Ph.D.

Advisors

DeWoody, Purdue University.

Subject Area

Zoology|Forestry

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