Discordant introgression in a rapidly expanding hybrid swarm
Version of Record online: 20 MAR 2012
© 2012 The Authors. Evolutionary Applications published by Blackwell Publishing Ltd.
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
Volume 5, Issue 4, pages 380–392, June 2012
How to Cite
Ward, J. L., Blum, M. J., Walters, D. M., Porter, B. A., Burkhead, N. and Freeman, B. (2012), Discordant introgression in a rapidly expanding hybrid swarm. Evolutionary Applications, 5: 380–392. doi: 10.1111/j.1752-4571.2012.00249.x
- Issue online: 24 APR 2012
- Version of Record online: 20 MAR 2012
- Received: 30 November 2011 Accepted: 9 December 2011
- Cyprinella ;
- hybrid zone;
- invasive species;
The erosion of species boundaries can involve rapid evolutionary change. Consequently, many aspects of the process remain poorly understood, including the formation, expansion, and evolution of hybrid swarms. Biological invasions involving hybridization present exceptional opportunities to study the erosion of species boundaries because timelines of interactions and outcomes are frequently well known. Here, we examined clinal variation across codominant and maternally inherited genetic markers as well as phenotypic traits to characterize the expansion and evolution of a hybrid swarm between native Cyprinella venusta and invasive Cyprinella lutrensis minnows. Discordant introgression of phenotype, microsatellite multilocus genotype, and mtDNA haplotype indicates that the observable expansion of the C. venusta × C. lutrensis hybrid swarm is a false invasion front. Both parental and hybrid individuals closely resembling C. lutrensis are numerically dominant in the expansion wake, indicating that the non-native parental phenotype may be selectively favored. These findings show that cryptic introgression can extend beyond the phenotypic boundaries of hybrid swarms and that hybrid swarms likely expand more rapidly than can be documented from phenotypic variation alone. Similarly, dominance of a single parental phenotype following an introduction event may lead to instances of species erosion being mistaken for species displacement without hybridization.