Structure of a mosaic hybrid zone between the field crickets Gryllus firmus and G. pennsylvanicus
Article first published online: 7 MAR 2013
© 2013 The Authors. Ecology and Evolution published by Blackwell Publishing Ltd.
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Ecology and Evolution
Volume 3, Issue 4, pages 985–1002, April 2013
How to Cite
Ecology and Evolution 2013; 3(4): 985–1002
- Issue published online: 11 APR 2013
- Article first published online: 7 MAR 2013
- Manuscript Accepted: 1 FEB 2013
- Manuscript Revised: 29 JAN 2013
- Manuscript Received: 28 NOV 2012
- National Science Foundation grant to RGH
- American Association for University Women American Fellowship to ELL
- Habitat association;
- reproductive isolation;
Hybrid zones provide insight into the nature of species boundaries and the evolution of barriers to gene exchange. Characterizing multiple regions within hybrid zones is essential for understanding both their history and current dynamics. Here, we describe a previously uncharacterized region of a well-studied hybrid zone between two species of field crickets, Gryllus pennsylvanicus and G. firmus. We use a combination of mitochondrial DNA sequencing, morphological data, and modeling of environmental variables to identify the ecological factors structuring the hybrid zone and define patterns of hybridization and introgression. We find an association between species distribution and natural habitat; Gryllus pennsylvanicus occupies natural habitat along forest edges and natural clearings, whereas G. firmus occupies more disturbed areas in agricultural and suburban environments. Hybridization and introgression occur across patch boundaries; there is evidence of substantial admixture both in morphological characters and mtDNA, over a broad geographic area. Nonetheless, the distribution of morphological types is bimodal. Given that F1 hybrids are viable and fertile in the lab, this suggests that strong pre-zygotic barriers are operating in this portion of the hybrid zone.