Genetic and Morphological Analysis of Hybridization Between Native and Invasive Pupfishes (Cyprinodon)

Authors: Jennifer Gumm, Kristina Ayers, Vance Imhoff, Gene Wilde

Year: 2018

Abstract

Invasive species can devastate native species and a main threat to endemic biodiversity is hybridization with introduced species. Cyprinodon variegatus is an invasive species that has impacted several other Cyprinodon species through rapid hybridization and genetic introgression. Cyprinodon rubrofluviatilis is native to the Brazos, Wichita and Red Rivers but collections between 2006-2012 showed intermediate morphological traits suggesting hybridization had occurred in the Brazos River. We investigated if C. variegatus was present and hybridizing in the Brazos River and identify the extent of introgression between the two species. We used molecular and morphological approaches to analyze specimens collected between 2013-2017 from the Brazos, Wichita, and Red Rivers and the Gulf of Mexico. In 2014-2015, low levels of introgression were evident, but hybridization was not widespread in the Brazos. In more recent sampling (2016-2017), genetic structure differed from previous years and there were no longer signs genetic signs of hybridization. Morphological analysis showed clear differences between species with little evidence of intermediate phenotypes. Although hybridization between C. variegatus and C. rubrofluviatilis is not currently widespread, there has been a complex pattern of hybridization in the past and it remains a threat to native Cyprinodon in this region.