Does courtship behavior contribute to species-level reproductive isolation in field crickets?

Reproductive behavior influences gene flow within and among species; thus, sexual selection may be a major contributor to the maintenance of species, and possibly their formation. Here I experimentally manipulate the courtship interactions of the field crickets Gryllus rubens and G. texensis to examine the potential of close-range courtship interactions to limit interspecific gene flow. Responses of males to females and of females to male courtship song and males per se were examined for four paired sympatric and allopatric populations. Male G. rubens were more likely to court conspecific females, but male G. texensis courted females of both species equally. If paired with conspecific males, female G. rubens and G. texensis both preferred conspecific courtship song. In none of these comparisons were the responses of males or females from allopatry different from those in sympatry. There was an asymmetry of courtship response across both sex and species: male G. rubens were more discriminating than male G. texensis, whereas female G. texensis were more discriminating than female G. rubens. Despite significant preferences for conspecifics, the net effect of courtship interactions would appear to limit interspecific gene flow only weakly. These results are consistent with courtship behavior evolving under the influence of sexual selection and only indirectly promoting species integrity.