03461nas a2200169   4500008004100000022001400041245011700055210006900172260001600241300000700257490000700264520290600271100002403177700002103201700002003222856004903242       2022                        eng d  a1741-700700aMating behavior and reproductive morphology predict macroevolution of sex allocation in hermaphroditic flatworms0 aMating behavior and reproductive morphology predict macroevoluti  cFeb-07-2022  a350 v203 a<p><jats title="">Abstract</jats><jats sec=""> <jats title="">Background</jats> <jats p="">Sex allocation is the distribution of resources to male or female reproduction. In hermaphrodites, this concerns an individual&rsquo;s resource allocation to, for example, the production of male or female gametes. Macroevolutionary studies across hermaphroditic plants have revealed that the self-pollination rate and the pollination mode are strong predictors of sex allocation. Consequently, we expect similar factors such as the selfing rate and aspects of the reproductive biology, like the mating behaviour and the intensity of postcopulatory sexual selection, to predict sex allocation in hermaphroditic animals. However, comparative work on hermaphroditic animals is limited. Here, we study sex allocation in 120 species of the hermaphroditic free-living flatworm genus <jats italic="">Macrostomum</jats>. We ask how hypodermic insemination, a convergently evolved mating behaviour where sperm are traumatically injected through the partner&rsquo;s epidermis, affects the evolution of sex allocation. We also test the commonly-made assumption that investment into male and female reproduction should trade-off. Finally, we ask if morphological indicators of the intensity of postcopulatory sexual selection (female genital complexity, male copulatory organ length, and sperm length) can predict sex allocation.</jats> </jats><jats sec=""> <jats title="">Results</jats> <jats p="">We find that the repeated evolution of hypodermic insemination predicts a more female-biased sex allocation (i.e., a relative shift towards female allocation). Moreover, transcriptome-based estimates of heterozygosity reveal reduced heterozygosity in hypodermically mating species, indicating that this mating behavior is linked to increased selfing or biparental inbreeding. Therefore, hypodermic insemination could represent a selfing syndrome. Furthermore, across the genus, allocation to male and female gametes is negatively related, and larger species have a more female-biased sex allocation. Finally, increased female genital complexity, longer sperm, and a longer male copulatory organ predict a more male-biased sex allocation.</jats> </jats><jats sec=""> <jats title="">Conclusions</jats> <jats p="">Selfing syndromes have repeatedly originated in plants. Remarkably, this macroevolutionary pattern is replicated in <jats italic="">Macrostomum</jats> flatworms and linked to repeated shifts in reproductive behavior. We also find a trade-off between male and female reproduction, a fundamental assumption of most theories of sex allocation. Beyond that, no theory predicts a more female-biased allocation in larger species, suggesting avenues for future work. Finally, morphological indicators of more intense postcopulatory sexual selection appear to predict more intense sperm competition.</jats> </jats></p>
1 aBrand, Jeremias, N.1 aHarmon, Luke, J.1 aSchärer, Lukas  uhttp://dx.doi.org/10.1186/s12915-022-01234-101939nas a2200169   4500008004100000022002500041245010500066210006900171260001600240300001000256490000600266520139300272100002401665700002101689700002001710856003901730       2021                        eng d  a2056-3744, 2056-374400aFrequent origins of traumatic insemination involve convergent shifts in sperm and genital morphology0 aFrequent origins of traumatic insemination involve convergent sh  cDec-30-2021  a63-820 v63 a<p>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.</p>
1 aBrand, Jeremias, N.1 aHarmon, Luke, J.1 aSchärer, Lukas  uhttp://dx.doi.org/10.1002/evl3.268