title: Molecular evidence for hybridization in Colias (Lepidoptera: Pieridae): are Colias hybrids really hybrids?
abstract: Gene flow and hybridization among species dramatically affect our understanding of the species as a biological unit, species relationships, and species adaptations. In North American Colias eurytheme and Colias eriphyle, there has been historical debate over the extent of hybridization occurring and the identity of phenotypically intermediate individuals as genetic hybrids. This study assesses the population structure of these two species to measure the extent of hybridization and the genetic identity of phenotypic intermediates as hybrids. Amplified fragment length polymorphism (AFLP) marker analysis was performed on 378 specimens collected from northern California and Nevada. Population structure was inferred using a Bayesian/Markov chain Monte Carlo method, which probabilistically assigns individuals to genetic clusters. Three genetic clusters provided the best fit for the data. C. eurytheme individuals were primarily assigned to two closely related clusters, and C. eriphyle individuals were mostly assigned to a third, more distantly related cluster. There appeared to be significant hybridization between the two species. Individuals of intermediate phenotype (putative hybrids) were found to be genetically indistinguishable from C. eriphyle, indicating that previous work based on the assumption that these intermediate forms are hybrids may warrant reconsideration.
authors: Eberly Center for Teaching Excellence and Educational Innovation, Carnegie Mellon University Pittsburgh, Pennsylvania, 15213.
authors: Heather E
authors: HE
authors: Dwyer
authors: Department of Plant Sciences, University of California Davis, California, 95616.
authors: Marie
authors: M
authors: Jasieniuk
authors: Department of Plant Sciences, University of California Davis, California, 95616.
authors: Miki
authors: M
authors: Okada
authors: Department of Evolution and Ecology, University of California Davis, California, 95616.
authors: Arthur M
authors: AM
authors: Shapiro
keywords: Amplified fragment length polymorphism; Colias eriphyle; Colias eurytheme; hybridization; population structure