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

Abstract Background Sex allocation is the distribution of resources to male or female reproduction. In hermaphrodites, this concerns an individual’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 Macrostomum. We ask how hypodermic insemination, a convergently evolved mating behaviour where sperm are traumatically injected through the partner’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. Results 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. Conclusions Selfing syndromes have repeatedly originated in plants. Remarkably, this macroevolutionary pattern is replicated in Macrostomum 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.

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

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.

1 aBrand, Jeremias, N.1 aHarmon, Luke, J.1 aSchärer, Lukas uhttp://dx.doi.org/10.1002/evl3.26802316nas a2200193 4500008004100000022001400041245012300055210006900178260001600247300001100263490000800274520168200282100002401964700002101988700002102009700002202030700002002052856005002072 2022 eng d a1055-790300aLarge-scale phylogenomics of the genus Macrostomum (Platyhelminthes) reveals cryptic diversity and novel sexual traits0 aLargescale phylogenomics of the genus Macrostomum Platyhelminthe cJan-01-2022 a1072960 v1663 a

Free-living flatworms of the genus Macrostomum are small and transparent animals, representing attractive study organisms for a broad range of topics in evolutionary, developmental, and molecular biology. The genus includes the model organism M. lignano for which extensive molecular resources are available, and recently there is a growing interest in extending work to additional species in the genus. These endeavours are currently hindered because, even though >200 Macrostomum species have been taxonomically described, molecular phylogenetic information and geographic sampling remain limited. We report on a global sampling campaign aimed at increasing taxon sampling and geographic representation of the genus. Specifically, we use extensive transcriptome and single-locus data to generate phylogenomic hypotheses including 145 species. Across different phylogenetic methods and alignments used, we identify several consistent clades, while their exact grouping is less clear, possibly due to a radiation early in Macrostomum evolution. Moreover, we uncover a large undescribed diversity, with 94 of the studied species likely being new to science, and we identify multiple novel morphological traits. Furthermore, we identify cryptic speciation in a taxonomically challenging assemblage of species, suggesting that the use of molecular markers is a prerequisite for future work, and we describe the distribution of putative synapomorphies and suggest taxonomic revisions based on our finding. Our large-scale phylogenomic dataset now provides a robust foundation for comparative analyses of morphological, behavioural and molecular evolution in this genus.

1 aBrand, Jeremias, N.1 aViktorin, Gudrun1 aWiberg, Axel, W.1 aBeisel, Christian1 aSchärer, Lukas uhttp://dx.doi.org/10.1016/j.ympev.2021.10729602465nas a2200181 4500008004100000245015400041210006900195300001200264490000700276520181500283100002002098700002402118700001802142700002502160700002502185700002102210856005202231 2020 eng d00aA phylogenetically informed search for an alternative Macrostomum model species, with notes on taxonomy, mating behavior, karyology, and genome size.0 aphylogenetically informed search for an alternative Macrostomum  a41–650 v583 a

The free-living flatworm Macrostomum lignano is used as a model in a range of research fields—including ageing, bioadhesion, stem cells, and sexual selection—leading to the recent establishment of genome assemblies and transgenics. However, the Macrostomum community has run into a roadblock following the discovery of an unusual genome organization in M. lignano, which could impair the development of essential resources and tools. Briefly, M. lignano has undergone a whole-genome duplication, followed by rediploidisation into a 2n=8 karyotype (distinct from the canonical 2n=6 karyotype in the genus). Although this karyotype appears visually diploid, it is in fact a hidden tetraploid (with rarer 2n=9 and 2n=10 individuals being pentaploid and hexaploid, respectively). Here we report on a phylogenetically-informed search for close relatives of M. lignano, aimed at uncovering alternative Macrostomum models with the canonical karyotype and a simple genome organization. We taxonomically describe three new species: the first, Macrostomum janickei n. sp., is the closest known relative of M. lignano, and shares its derived genome organization; the second, Macrostomum mirumnovem n. sp., has an even more unusual genome organization, with a highly variable karyotype based on a 2n=9 base pattern; and the third, Macrostomum cliftonensis n. sp., does not only show the canonical 2n=6 karyotype, but also performs well under standard laboratory culture conditions and fulfils many other requirements. M. cliftonensis is a viable candidate for replacing M. lignano as the primary Macrostomum model, being outcrossing and having an estimated haploid genome size of only 231 Mbp.

1 aSchärer, Lukas1 aBrand, Jeremias, N.1 aSingh, Pragya1 aZadesenets, Kira, S.1 aStelzer, Claus-Peter1 aViktorin, Gudrun uhttps://macrostomorpha.myspecies.info/node/4774