Undergraduate Honors Theses

Thesis Defended

Spring 2013

Document Type



Environmental Studies

First Advisor

Dr. Alexander Cruz

Second Advisor

Dale Miller

Third Advisor

Dr. Andrew Martin


The subfamily Goodeinae consists of thirty-six matrotrophic viviparous species, all of which are endemic to Mexico (Webb et al. 2004). Xenotoca eiseni, a species within the subfamily Goodeinae, is sexually dimorphic in hue and varies geographically in its coloration (Fitzsimons 1970). Currently, six or seven natural populations remain (Lyons 2011). Fortunately, X. eiseni is raised in many aquariums and is commonly traded amongst hobbyists. Therefore populations of X. eiseni can be reintroduced into extant populations (Dominguez-Dominguez et al. 2005). Natural populations suffer from habitat degradation and invasive species (Lyons 2011, Domínguez-Domínguez et al. 2005). They are currently not listed as endangered as they have little economic value and have not been assessed by the International Union for Conservation of Nature (IUCN 2012). However, many national and international researches use X. eiseni and other Goodeidae as model organisms for evolutionary, biogeographic and livebearer studies (Domínguez-Domínguez et al. 2005). This study is designed to use a variety of methods to see how sexual selection and breeding biology play a role in the conservation of the threatened X. eiseni. Male Goodeinae cannot successfully mate with females without the female possessing an interest in the male. This is because the males do not possess a true gonopodium. X. eiseni males therefore possess an elaborate courtship behavior when seeking a mate (Kingston 1970). This study showed that large females show a disinterest in small males and males that exhibit relatively less coloration than the more colorful males. Therefore when reestablishing populations of X. eiseni males should be closely matched in color to the extant populations to ensure successful copulation and sustain populations of this unique Mexican treasure in the future.