Fluctuating asymmetry and reproductive isolation between two sticklebacks

This paper describes patterns of developmental asymmetry in a limnetic-benthic stickleback species pair from Paxton Lake, British Columbia. Three gill raker characters and one armor character were compared among full-sib parental crosses and their hybrids (F₁, F₂ and backcrosses). All crosses displayed asymmetry, but no differences in mean or fluctuating asymmetry were detected among laboratory-reared crosses. When wild-caught limnetics and benthics were included in the analyses significant differences in FA among groups were detected in gill raker length and plate number. The effect appears to be solely due to wild-caught benthics, though the reasons for their greater asymmetry are unknown. The patterns in laboratory-reared crosses suggest that asymmetry is unlikely to promote reproductive isolation between the parental species.