Date of Award

Spring 5-2015

Degree Type

Honors College Thesis


Biological Sciences

First Advisor

Jake Schaefer

Advisor Department

Biological Sciences


The evolution of body size has long been a topic of interest to biologists due to the close link between size and various aspects of an organism’s biology. Adult body size is influenced by the underlying tradeoff in energy allocation between maintenance, somatic growth and reproduction. I studied the evolution of a large group of globally distributed (primarily freshwater with some marine forms) fishes to test some basic hypotheses about the evolution of adult body size. Catfish (Siluriformes) are an excellent group for this type of research as they represent approximately 11% of fishes and species range in size from over three meters (family Pangasiidae) to a few centimeters (family Trichomycteridae). Because they are such a large and diverse group, we worked at the genera level and compiled sequence data for construction of a phylogeny along with body size, body shape, distribution and ecological data. The final dataset included 212 genera representing over 2,400 species. We first tested for the strength of phylogenetic signal in body size. Next, we used phylogenetic least squared methods to test for the effects of distribution (range size and latitude), habitat (freshwater vs. marine), trophic ecology and body shape on body size in catfish. Because we worked at the genera level, we were also able to quantify and analyze patterns of variability in body shape within groups (coefficient of variation in size within a genera).

Included in

Evolution Commons