A POSTINSEMINATION BARRIER TO FERTILIZATION ISOLATES TWO CLOSELY RELATED GROUND CRICKETS.

Postinsemination barriers to fertilization generally have been ignored by biologists interested in the origin and nature of reproductive isolation among closely related terrestrial animals. Yet evidence presented in this paper indicates that such a barrier bears primary responsibility for the reproductive isolation between the ground crickets Allonemobius fasciatus and Allonemobius socius. Postinsemination barriers to fertilization may isolate many other terrestrial animals as well, but the design of most laboratory hybridization experiments precludes the detection of these barriers. © 1994 The Society for the Study of Evolution.