Present address: Department of Biology, University of New Mexico, MSC03 2020, 1 University of New Mexico Way, Albuquerque, NM 87131-0001, USA.
Relationships between spatio-temporal environmental and genetic variation reveal an important influence of exogenous selection in a pupfish hybrid zone
Article first published online: 23 JAN 2012
© 2012 Blackwell Publishing Ltd
Volume 21, Issue 5, pages 1209–1222, March 2012
How to Cite
CARSON, E. W., TOBLER, M., MINCKLEY, W. L., AINSWORTH, R. J. and DOWLING, T. E. (2012), Relationships between spatio-temporal environmental and genetic variation reveal an important influence of exogenous selection in a pupfish hybrid zone. Molecular Ecology, 21: 1209–1222. doi: 10.1111/j.1365-294X.2011.05433.x
- Issue published online: 23 FEB 2012
- Article first published online: 23 JAN 2012
- Received 20 September 2011; revision received 25 November 2011; accepted 30 November 2011
- Cuatro Ciénegas basin;
- environmental variation;
- nuclear introns
The importance of exogenous selection in a natural hybrid zone between the pupfishes Cyprinodon atrorus and Cyprinodon bifasciatus was tested via spatio-temporal analyses of environmental and genetic change over winter, spring and summer for three consecutive years. A critical influence of exogenous selection on hybrid zone regulation was demonstrated by a significant relationship between environmental (salinity and temperature) and genetic (three diagnostic nuDNA loci) variation over space and time (seasons) in the Rio Churince system, Cuatro Ciénegas, Mexico. At sites environmentally more similar to parental habitats, the genetic composition of hybrids was stable and similar to the resident parental species, whereas complex admixtures of parental and hybrid genotypic classes characterized intermediate environments, as did the greatest change in allelic and genotypic frequencies across seasons. Within hybrids across the entire Rio Churince system, seasonal changes in allelic and genotypic frequencies were consistent with results from previous reciprocal transplant experiments, which showed C. bifasciatus to suffer high mortality (75%) when exposed to the habitat of C. atrorus in winter (extreme temperature lows and variability) and summer (abrupt salinity change and extreme temperature highs and variability). Although unconfirmed, the distributional limits of C. atrorus and C. atrorus-like hybrids appear to be governed by similar constraints (predation or competition). The argument favouring evolutionary significance of hybridization in animals is bolstered by the results of this study, which links the importance of exogenous selection in a contemporary hybrid zone between C. atrorus and C. bifasciatus to previous demonstration of the long-term evolutionary significance of environmental variation and introgression on the phenotypic diversification Cuatro Ciénegas Cyprinodon.