Looking for a mate? Oh, whatever

From Atlanta, Ga., at the annual meeting of the Animal Behavior Society

Two ground cricket species seem rather casual about telling themselves apart, and biologists are wondering why.

The two crickets, Allonemobius fasciatus and Allonemobius socius, can produce hybrids, reports James H. Benedix of DePauw University in Greencastle, Ind. Yet the hybrids don’t thrive.

In theory, such results of interspecies romance could lead the two species to develop exaggerated differences where their ranges overlap. Such exaggerations, called reproductive-character displacements, help delineate species.

However, Benedix and Daniel Howard of New Mexico State University in Las Cruces haven’t found displacements in the male suitors’ songs or in the females’ tastes. When Benedix offered a choice of mates, neither species seemed to prefer its own.

A mistake may not be all that costly, Benedix points out. Interspecies encounters don’t yield dead-end hybrids as long as a female also mates with her own kind. That’s because same-species sperm take precedence in fertilizing eggs.

A female actually may benefit from cross-species mates, says Benedix. The sperm packages males provide during mating harbor nutrition, but males often seem reluctant to release them. A female may mate with whomever she can, therefore, simply to satisfy her nutritional needs.

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.