The Evolution of Female-Biased Genital Diversity in Bedbugs (Cimicidae).

Rapid genitalia evolution is believed to be mainly driven by sexual selection. Recently, non-copulatory genital functions have been suggested to exert stronger selection pressure on female genitalia than copulatory functions. In bedbugs (Cimicidae), the impact of the copulatory function can be isolated from the non-copulatory impact. Unlike in other taxa, female copulatory organs have no function in egg-laying or waste-product expulsion. Males perform traumatic mating by piercing the female integument, thereby imposing antagonistic selection on females and suspending selection to morphologically match the female genitalia. Females show strong interspecific variation in the location of the copulatory organ. It evolved rapidly, changing twice between dorsal and ventral side, and several times along the anteroposterior, and the left-right axes. Male genital length and shape varied much less, did not appear to follow the positional changes seen in females, and showed no evidence for coevolution: the number of simultaneous changes in male and female genital traits did not differ from chance. Female genitalia position evolved 1.5 times faster than male genital length and shape and showed little neutral or geographic signals. Instead we propose that non-morphological male traits, such as mating behaviour, may drive female genitalia morphology in this taxon. Models of genitalia evolution may benefit from considering morphological genital responses to non-morphological stimuli, such as male mating behaviour or copulatory position.

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© The Author(s) 2023. Published by Oxford University Press on behalf of The Society for the Study of Evolution (SSE).