Ecology and Evolutionary Biology

Ecology and Evolutionary Biology

Doctoral Program

Dissertation Proposal – Steven Bovio

Stephen Bovio (EEB student, Rosenthal Lab) will be defending his dissertation proposal this Thursday, April 11 and everyone is invited to attend the public portion of the proposal defense (info below).  His public presentation will be at 2 pm in WFES 411.

His talk title is Evolutionary consequences of natural and sexual selection on hybridizing swordtails

Summary: Hybridization is a common phenomenon that serves as an important evolutionary mechanism by which diversity can arise. When two genetically divergent species hybridize, the resulting admixture generates novel genotypic and phenotypic combinations that selection can act upon. In the Rosenthal lab, we study two freshwater species of fish, Xiphophorus birchmanni and X. malinche, that form natural replicated hybrid zones in the Sierra Madre Oriental in Hdg, MX. The birchmanni-malinche system offers a unique opportunity to study long-standing evolutionary questions regarding the consequences of ecological and sexual selection on hybrid populations due to their unique natural history and ecological circumstances. Xiphophorus malinche are found at high elevations while X. birchmanni are found at lower elevations – at intermediate elevations, hybrids form. The core of my dissertation will focus on the collection and analysis of data generated from our long-term research project aimed at monitoring hybrid evolution for ten generations. Replicated mesocosms at high, intermediate, and low elevations initially seeded with F1 hybrids will enable me to characterize changes in phenotypes and genotypes for early generation hybrids. Specifically, I will investigate how thermal selection and pre- and postmating sexual selection act on early generation hybrid populations.

EEB Proposal Defense – Mateo Garcia

Mateo Garcia (EEB student, Rosenthal Lab) will be defending his dissertation proposal Tuesday, March 19 and everyone is invited to attend the public portion of the proposal defense (info below).  His public presentation will be at 10 am in WFES 236.
His talk title is NATURAL HYBRIDIZATION AND MELANOMA IN SWORDTAIL FISH
Summary:  A growing literature has called attention to the importance of hybridization to the evolutionary process. When species hybridize, alleles that are benign in their specific genetic background can be deleterious or disadvantageous in the alternative background generating a variety of phenotypic consequences being cancer, more specifically melanoma,  one of them. Swordtails are the oldest animal model for the study of melanoma. Enforced hybridization under laboratory conditions has identified an epistatic interaction that affects pigmentation and can even induce melanoma development. X. birchmanni and X. malinche produce viable hybrids along several populations in the Sierra Madre (Hidalgo, Mexico) that present a macromelanophore pigment pattern called Spotted Caudal (Sc), which varies in its expression from a few black spots to extreme melanosis and eventually malignant melanoma. Combining population genomic studies in parental and hybrid populations we have identified a primary oncogene driving the expression of Sc as well as two tumor modifier candidate genes responsible for the switch from benign to malignant pigmentation. I am carrying out transgenic studies to characterize the modifying effect of these genes have on Sc-tumor development. Moreover, the frequency of Sc is significantly higher in males than in females suggesting that the expression of the phenotype might be affected by androgens. Testosterone treatments on females will inform us about relevant physiological and genetic interactions. Finally, higher Sc frequencies in juveniles compared to adults suggests that selection against Sc juveniles must be balanced by some source of positive selection on the phenotype in adults. The hypothesis that Sc may be under sexual selection either by female mate choice or male-male competition will be tested by several behavioral assays.

PI: Gil Rosenthal
Co-PI: Manfred Schartl
Committee: Kirk Winemiller, Heath Blackmon