02316nas 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