Historical influences on genital morphology among sympatric species: gonopod evolution and reproductive isolation in the crayfish genus Orconectes (Cambaridae)

Freshwater crayfishes represent an incredibly diverse component of temperate aquatic ecosystems. The genus Orconectes (Cambaridae) comprises approximately 17% of total global crayfish diversity and is native to central and eastern North America. Using both Bayesian and parsimony‐based phylogenetic hypotheses from complete cytochrome c oxidase subunit I (COI) mtDNA sequence data (1545 bp) along with information on male gonopod shape and species distribution patterns, we examined the evolution of male genital morphology and its potential influence on species co‐occurrence. We found that sympatric species exhibited similar male genital morphology more often than expected based on the frequency of genital shapes within the genus. When evolutionary history was incorporated into this analysis, the result was no longer significant, suggesting that species co‐occurrence and the associated genital shapes of sympatric congeners cannot be explained solely by interspecific ecological interactions. Our results also do not support the current subgeneric classifications within Orconectes or the monophyly of the genus, both of which have been based previously on male genital morphology. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 1–12.