• Open Access

Divergence in genital morphology may contribute to mechanical reproductive isolation in a millipede

Authors

  • Janine M. Wojcieszek,

    1. Centre for Evolutionary Biology, School of Animal Biology M092, University of Western Australia, Crawley, Western Australia, Australia
    Current affiliation:
    1. School of Veterinary and Biomedical Sciences, Murdoch University, Murdoch, Western Australia, Australia
    Search for more papers by this author
  • Leigh W. Simmons

    Corresponding author
    • Centre for Evolutionary Biology, School of Animal Biology M092, University of Western Australia, Crawley, Western Australia, Australia
    Search for more papers by this author

Correspondence

LW Simmons, Centre for Evolutionary Biology, School of Animal Biology M092, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia. Tel: +61 8 6488 2221; Fax: +61 8 6488 1029; E-mail: leigh.simmons@uwa.edu.au

Abstract

Genitalia appear to evolve rapidly and divergently in taxa with internal fertilization. The current consensus is that intense directional sexual selection drives the rapid evolution of genitalia. Recent research on the millipede Antichiropus variabilis suggests that the male genitalia are currently experiencing stabilizing selection – a pattern of selection expected for lock-and-key structures that enforce mate recognition and reproductive isolation. Here, we investigate how divergence in genital morphology affects reproductive compatibility among isolated populations of A. variabilis. Females from a focal population were mated first to a male from their own population and, second, to a male from one of two populations with divergent genital morphology. We observed variation in mating behavior that might indicate the emergence of precopulatory reproductive barriers: males from one divergent population took significantly longer to recognize females and exhibited mechanical difficulty in genital insertion. Moreover, we observed very low paternity success for extra-population males who were successful in copulating. Our data suggest that divergence in genital shape may be contributing to reproductive isolation, and incipient speciation among isolated populations of A. variabilis.

Ancillary