Evolution Ultragroup

Today will be the last Evolution Ultragroup seminar for the Spring 2011 semester. Please join us to hear Jose Lopez talk about his proposed dissertation research in Dr. Rachel Mueller’s lab.

The role of epigenetics, transposable elements, and genome size variation in speciation

Abstract: Species formation occurs when lineages diverge and incompatibilities between their genomes lead to reproductive isolation. Such incompatibilities can involve genomic content (including protein coding and regulatory sequences, as well as repetitive DNA) or overall genome architecture (including karyotype, epigenetic marks, genome size). To date, most theoretical and empirical research focused on the genetics of speciation has examined the protein-coding portion of the genome. I am interested in testing hypothesis about the potential role of transposable elements, cytosine methylation, and genome size variation in establishing isolating barriers. Salamanders provide a good system in which to test these hypotheses because they 1) have very large genomes with large numbers of transposable elements, 2) methylation levels are higher in amphibians than in most other animals, and 3) significant intra-specific genome size variation exists. The salamander Ensatina eschscholtzii is an ideal system in which to investigate speciation. E. eschscholtzii is comprised of seven subspecies distributed in a ring around the Central Valley of California and is a classic example of a ring species. Although adjacent subspecies are generally connected by some gene flow, their levels of genetic differentiation are comparable to closely related species, and the two southernmost subspecies show nearly complete reproductive isolation where they reconnect at the base of the Central Valley. Thus E. eschscholtzii provides a perfect system in which to study whether differences in genome size, transposable elements, and methylation can produce genomic incompatibilities and establish reproductive isolation.