A major goal of evolutionary biologists is to determine how closely related species keep from interbreeding. This is often a result of differences in behavior, such as when females of two species differ in their preferences for particular mates. These preferences can be highly sensitive to changes in the environment. The aim of this study is to discover how female preferences in swordtail fish are affected by different environmental factors. This study is among the first to attempt to assess how the environment affects the molecular basis of sensory perception and mating behavior. Furthermore, this study will shed light on how environmental conditions can promote interbreeding and therefore affect how species split apart and come together. Throughout the course of this study, the researchers will train undergraduate students at Texas A&M as well as local students from Calnali, Mexico. These students will help in conducting experiments, thereby receiving a firsthand experience with research and becoming well-rounded scientists. This training will increase interest in ecology an evolutionary biology and, in the case of Calnali, will create exemplary scientists in a region where there are few.
Specifically, the researchers will use the swordtail fish Xiphophorus birchmanni to determine which genes in the brain and sensory tissue are sensitive to changes in female diet and her social environment, and how these environmental factors affect female preference for males of the same species. Newborn swordtails will be submitted to one of three social treatments (raised with adult conspecifics, adult heterospecific Xiphophorus malinche, or no adult exposure) and one of two diet treatments, varying in protein content, which has been shown to affect the strength of female swordtail preference. Upon maturation, female preference for conspecific versus heterospecific male odors will be assessed using a dichotomous mate choice assay. Female brains and olfactory epithelia will then be dissected and undergo RNA-Seq analyses to quantify gene expression. The researchers will then use in situ hybridization on candidate genes found from RNA-Seq to identify where these genes are expressed and therefore what brain regions are implicated in female mate choice. Tissue samples and extracted RNA will be archived in the Texas A&M University Biodiversity Research and Teaching Collections. Whole specimens will be accessioned to the Ichthyology collection of UNAM, Mexico. Data collected will be backed up on two workstations and a dedicated external drive. Data associated with accepted manuscripts will be archived in appropriate electronic repositories.
