Open AccessFrequent origins of traumatic insemination involve convergent shifts in sperm and genital morphology
Author(s) -
Brand Jeremias N.,
Harmon Luke J.,
Schärer Lukas
Publication year - 2022
Publication title -
evolution letters
Language(s) - English
Resource type - Journals
ISSN - 2056-3744
DOI - 10.1002/evl3.268
Subject(s) - insemination , biology , sperm competition , sperm , mating , sexual selection , sexual conflict , sex organ , antagonistic coevolution , female sperm storage , evolutionary biology , zoology , donor insemination , reproductive success , artificial insemination , pregnancy , genetics , medicine , population , environmental health
Traumatic insemination is a mating behavior during which the (sperm) donor uses a traumatic intromittent organ to inject an ejaculate through the epidermis of the (sperm) recipient, thereby frequently circumventing the female genitalia. Traumatic insemination occurs widely across animals, but the frequency of its evolution, the intermediate stages via which it originates, and the morphological changes that such shifts involve remain poorly understood. Based on observations in 145 species of the free‐living flatworm genus Macrostomum , we identify at least nine independent evolutionary origins of traumatic insemination from reciprocal copulation, but no clear indication of reversals. These origins involve convergent shifts in multivariate morphospace of male and female reproductive traits, suggesting that traumatic insemination has a canalizing effect on morphology. We also observed sperm in both the sperm receiving organ and within the body tissue of two species. These species had intermediate trait values indicating that traumatic insemination evolves through initial internal wounding during copulation. Finally, signatures of male‐female coevolution of genitalia across the genus indicate that sexual selection and sexual conflict drive the evolution of traumatic insemination, because it allows donors to bypass postcopulatory control mechanisms of recipients.