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International Journal of Ecology
Volume 2012, Article ID 809897, 8 pages
Research Article

Testing the Role of Habitat Isolation among Ecologically Divergent Gall Wasp Populations

1Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
2Advanced Diagnostics and Therapeutics, University of Notre Dame, Notre Dame, IN 46556, USA
3Population and Conservation Biology Program, Department of Biology, Texas State University—San Marcos, San Marcos, TX 78666, USA

Received 17 October 2011; Accepted 9 January 2012

Academic Editor: Marianne Elias

Copyright © 2012 Scott P. Egan et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Habitat isolation occurs when habitat preferences lower the probability of mating between individuals associated with differing habitats. While a potential barrier to gene flow during ecological speciation, the effect of habitat isolation on reproductive isolation has rarely been directly tested. Herein, we first estimated habitat preference for each of six populations of the gall wasp Belonocnema treatae inhabiting either Quercus virginiana or Q. geminata. We then estimated the importance of habitat isolation in generating reproductive isolation between B. treatae populations that were host specific to either Q. virginiana or Q. geminata by measuring mate preference in the presence and absence of the respective host plants. All populations exhibited host preference for their native plant, and assortative mating increased significantly in the presence of the respective host plants. This host-plant-mediated assortative mating demonstrates that habitat isolation likely plays an important role in promoting reproductive isolation among populations of this host-specific gall former.