Date of Award
Doctor of Philosophy
Ecology, Evolution, and Organismal Biology
Ecology and Evolutionary Biology
One of the most studied areas in the field of evolutionary biology is the formation and maintenance of new species, as well as variation in the rate and extent to which taxa radiate. A range of evolutionary processes, from ecological adaptation to sexual selection and reinforcement, can lead species formation. However, the generation of new species likely results from several isolating mechanisms acting in concert. The map turtle complex (genus: Graptemys) is an excellent model system for exploring the nature of speciation given its exceptional species richness and morphological diversity, particularly in facial coloration patterns. This research utilizes an integrative approach to establish the role of post-orbital color patterns in species diversification and maintenance. This multi-faceted approach will incorporate phylogenetics, population and quantitative genetics, morphometrics, and behavior to assess morphological evolution within species and across the genus. The phylogeny of map turtles was characterized by a hard polytomy indicating rapid speciation. Across the genus, morphological evolution occurred parsimoniously. Within species, both morphology and genetics exhibited a pattern of isolation by distance. Temperature significantly influences coloration patterns and multivariate heritability was generally low. Finally, in behavior trials, neither males nor females spent significantly more time with members of their own species. In all projects, the signatures of sexual selection or reinforcement were absent or equivocal where they would be expected if they were the main forces continuing to shape interactions among map turtle species. The results of this research indicate that role of past and on-going selection on coloration pattern within the map turtle clade has been limited, thus post-orbital coloration was not the driving factor in the radiation of this turtle clade. Alternative explanations for map turtle species richness are explored.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Erin M. Myers
Myers, Erin M., "Post-orbital color pattern variation and the evolution of a radiation of turtles (Graptemys)" (2008). Retrospective Theses and Dissertations. 15749.