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CRYPTIC POSTZYGOTIC ISOLATION IN AN ERUPTIVE SPECIES OF BARK BEETLE ( DENDROCTONUS PONDEROSAE )
Author(s) -
Bracewell Ryan R.,
Pfrender Michael E.,
Mock Karen E.,
Bentz Barbara J.
Publication year - 2011
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/j.1558-5646.2010.01201.x
Subject(s) - reproductive isolation , biology , dendroctonus , evolutionary biology , gene flow , hybrid zone , incipient speciation , coalescent theory , mountain pine beetle , genetics , ecology , population , genetic variation , bark beetle , gene , phylogenetics , bark (sound) , demography , sociology
Studies of postzygotic isolation often involve well‐differentiated taxa that show a consistent level of incompatibility, thereby limiting our understanding of the initial stages and development of reproductive barriers. Dendroctonus ponderosae provides an informative system because recent evidence suggests that distant populations produce hybrids with reproductive incompatibilities. Dendroctonus ponderosae shows an isolation‐by‐distance gene flow pattern allowing us to characterize the evolution of postzygotic isolation (e.g., hybrid inviability, hybrid sterility) by crossing populations along a continuum of geographic/genetic divergence. We found little evidence of hybrid inviability among these crosses. However, crosses between geographically distant populations produced sterile males (consistent with Haldane's rule). This effect was not consistent with the fixation of mutations in an isolation‐by‐distance pattern, but instead is spatially localized. These reproductive barriers are uncorrelated with a reduction in gene flow suggesting their recent development. Crosses between geographically proximal populations bounding the transition from compatibility to hybrid male sterility showed evidence of unidirectional reduction in hybrid male fecundity. Our study describes significant postzygotic isolation occurring across a narrow and molecularly cryptic geographic zone between the states of Oregon and Idaho. This study provides a view of the early stages of postzygotic isolation in a geographically widespread species.