Phylogeny of eastern North American leiobunine harvestmen (Opiliones: Sclerosomatidae) and coevolution of male and female reproductive structures

Species-specific variation in reproductive structures is a pervasive theme in arthropod evolution, but researchers differ on the mechanism of sexual selection that produces and maintains genitalic diversity. Here we reconstruct the phylogenetic relationships of North American leiobunine harvestmen using molecular data to determine the direction and frequency of evolutionary change in male and female genitalia to assess female choice and sexual conflict hypotheses. Our results show that the sacculate (nuptial gift-giving) condition is primitive within North American leiobunines and that it has been replaced by the lanceolate condition at least five times. Females in each lanceolate lineage have evolved unique and different pregenital barricades. This pattern is consistent with evolution of male mating strategy from female enticement to female coercion. Current evidence favors a sexual conflict explanation over female choice in shaping male and female genital structure and diversity.