Lucas Marie-Orleach

• Marie-Orleach, Lucas; Glémin, Sylvain; Brandrud, Marie Kristine; Brysting, Anne Krag; Seid, Abel Gizaw & Gustafsson, A Lovisa S [Show all 9 contributors for this article] (2024). How Does Selfing Affect the Pace and Process of Speciation? Cold Spring Harbor Perspectives in Biology. 16(11). doi: 10.1101/cshperspect.a041426. Full text in Research Archive Show summary

  Surprisingly little attention has been given to the impact of selfing on speciation, even though selfing reduces gene flow between populations and affects other key population genetics parameters. Here we review recent theoretical work and compile empirical data from crossing experiments and genomic and phylogenetic studies to assess the effect of mating systems on the speciation process. In accordance with theoretical predictions, we find that accumulation of hybrid incompatibilities seems to be accelerated in selfers, but there is so far limited empirical support for a predicted bias toward underdominant loci. Phylogenetic evidence is scarce and contradictory, including studies suggesting that selfing either promotes or hampers speciation rate. Further studies are therefore required, which in addition to measures of reproductive barrier strength and selfing rate should routinely include estimates of demographic history and genetic divergence as a proxy for divergence time.

• Fromonteil, Salomé; Marie-Orleach, Lucas; Winkler, Lennart & Janicke, Tim (2023). Sexual selection in females and the evolution of polyandry. PLoS Biology. ISSN 1544-9173. 21(1). doi: 10.1371/journal.pbio.3001916. Full text in Research Archive
• Marie-Orleach, Lucas; Brochmann, Christian & Glémin, Sylvain (2022). Mating system and speciation I: Accumulation of genetic incompatibilities in allopatry. PLoS Genetics. ISSN 1553-7390. 18(12). doi: 10.1371/journal.pgen.1010353. Full text in Research Archive Show summary

  Self-fertilisation is widespread among hermaphroditic species across the tree of life. Selfing has many consequences on the genetic diversity and the evolutionary dynamics of populations, which may in turn affect macroevolutionary processes such as speciation. On the one hand, because selfing increases genetic drift and reduces migration rate among populations, it may be expected to promote speciation. On the other hand, because selfing reduces the efficacy of selection, it may be expected to hamper ecological speciation. To better understand under which conditions and in which direction selfing affects the build-up of reproductive isolation, an explicit population genetics model is required. Here, we focus on the interplay between genetic drift, selection and genetic linkage by studying speciation without gene flow. We test how fast populations with different rates of selfing accumulate mutations leading to genetic incompatibilities. When speciation requires populations to pass through a fitness valley caused by underdominant and compensatory mutations, selfing reduces the depth and/or breadth of the valley, and thus overall facilitates the fixation of incompatibilities. When speciation does not require populations to pass through a fitness valley, as for Bateson-Dobzhanzky-Muller incompatibilities (BDMi), the lower effective population size and higher genetic linkage in selfing populations both facilitate the fixation of incompatibilities. Interestingly, and contrary to intuitive expectations, local adaptation does not always accelerate the fixation of incompatibilities in outcrossing relative to selfing populations. Our work helps to clarify how incompatibilities accumulate in selfing vs . outcrossing lineages, and has repercussions on the pace of speciation as well as on the genetic architecture of reproductive isolation.

• Gustafsson, A Lovisa S; Gussarova, Galina; Borgen, Liv; Ikeda, Hajime; Antonelli, Alexandre & Marie-Orleach, Lucas [Show all 8 contributors for this article] (2021). Rapid evolution of post-zygotic reproductive isolation is widespread in Arctic plant lineages. Annals of Botany. ISSN 0305-7364. 129(2), p. 171–184. doi: 10.1093/aob/mcab128. Full text in Research Archive Show summary

  Abstract Background and Aims The Arctic tundra, with its extreme temperatures and short growing season, is evolutionarily young and harbours one of the most species-poor floras on Earth. Arctic species often show little phenotypic and genetic divergence across circumpolar ranges. However, strong intraspecific post-zygotic reproductive isolation (RI) in terms of hybrid sterility has frequently evolved within selfing Arctic species of the genus Draba. Here we assess whether incipient biological species are common in the Arctic flora. Methods We conducted an extensive crossing experiment including six species representing four phylogenetically distant families collected across the circumpolar Arctic. We crossed conspecific parental populations representing different spatial scales, raised 740 F1 hybrids to maturity and measured fertility under laboratory conditions. We examined genetic divergence between populations for two of these species (Cardamine bellidifolia and Ranunculus pygmaeus). Key Results In five of the six species, we find extensive reduction in pollen fertility and seed set in F1 hybrids; 219 (46 %) of the 477 F1 hybrids generated between parents separated by ≥427 km had <20 % pollen fertility. Isolation with migration (IM) and *BEAST analyses of sequences of eight nuclear genes in C. bellidifolia suggests that reproductively isolated populations of this species diverged during, or even after, the last glaciation. Likewise, Arctic populations of R. pygmaeus were genetically very similar despite exhibiting strongly reduced fertility in crosses, suggesting that RI evolved recently also in this species. Conclusion We show that post-zygotic RI has developed multiple times within taxonomically recognized Arctic species belonging to several distantly related lineages, and that RI may have developed over just a few millennia. Rapid and widespread evolution of incipient biological species in the Arctic flora might be associated with frequent bottlenecks due to glacial cycles, and/or selfing mating systems, which are common in the harsh Arctic environment where pollinators are scarce.

• Marie-Orleach, Lucas; Vellnow, Nikolas & Schärer, Lukas (2021). The repeatable opportunity for selection differs between pre- and postcopulatory fitness components. Evolution Letters. 5(1), p. 101–114. doi: 10.1002/evl3.210. Full text in Research Archive Show summary

  In species with multiple mating, intense sexual selection may occur both before and after copulation. However, comparing the strength of pre- and postcopulatory selection is challenging, because (i) postcopulatory processes are generally difficult to observe and (ii) the often-used opportunity for selection (I) metric contains both deterministic and stochastic components. Here, we quantified pre- and postcopulatory male fitness components of the simultaneously hermaphroditic flatworm, Macrostomum lignano. We did this by tracking fluorescent sperm—using transgenics—through the transparent body of sperm recipients, enabling to observe postcopulatory processes in vivo. Moreover, we sequentially exposed focal worms to three independent mating groups, and in each assessed their mating success, sperm-transfer efficiency, sperm fertilizing efficiency, and partner fecundity. Based on these multiple measures, we could, for each fitness component, combine the variance (I) with the repeatability (R) in individual success to assess the amount of repeatable variance in individual success—a measure we call the repeatable opportunity for selection (IR). We found higher repeatable opportunity for selection in sperm-transfer efficiency and sperm fertilizing efficiency compared to mating success, which clearly suggests that postcopulatory selection is stronger than precopulatory selection. Our study demonstrates that the opportunity for selection contains a repeatable deterministic component, which can be assessed and disentangled from the often large stochastic component, to provide a better estimate of the strength of selection.

• Fromonteil, Salomé; Winkler, Lennart; Marie-Orleach, Lucas & Janicke, Tim (2021). Sexual selection in females across the animal tree of life. BioRxiv. ISSN 0362-4331. doi: 10.1101/2021.05.25.445581. Full text in Research Archive
• Marie-Orleach, Lucas; Sanz, Annui M.; Bailey, Nathan W. & Ritchie, Michael G. (2020). Does the response of D. melanogaster males to intrasexual competitors influence sexual isolation? Behavioral Ecology. ISSN 1045-2249. 30(2), p. 487–492. doi: 10.1093/beheco/arz209. Full text in Research Archive
• Janicke, Tim; Marie-Orleach, Lucas; Aubier, Thomas G; Perrier, Charles & Morrow, Edward H. (2019). Assortative Mating in Animals and Its Role for Speciation. The American Naturalist. ISSN 0003-0147. 194(6), p. 865–875. doi: 10.1086/705825. Full text in Research Archive
• Marie-Orleach, Lucas; Bailey, Nathan W. & Ritchie, Michael G. (2019). Social effects on fruit fly courtship song. Ecology and Evolution. 9, p. 410–416. doi: 10.1002/ece3.4759. Full text in Research Archive

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• Marie-Orleach, Lucas; Glémin, Sylvain; Brandrud, Marie Kristine; Brysting, Anne Krag; Gustafsson, Lovisa & Seid, Abel Gizaw [Show all 9 contributors for this article] (2024). How does selfing affect the pace and process of speciation? Full text in Research Archive
• Marie-Orleach, Lucas (2022). Quantifier les épisodes de sélection pré- et postcopulatoires. Full text in Research Archive
• Marie-Orleach, Lucas (2022). Effects of Sexual Reproduction on Evolution: Sexual Selection, Sexual Isolation, and Self-Fertilisation. Full text in Research Archive
• Marie-Orleach, Lucas; Brochmann, Christian & Glémin, Sylvain (2022). Theoretical Predictions on the Effects of Self-Fertilisation on Speciation. Full text in Research Archive
• Marie-Orleach, Lucas; Brochmann, Christian & Glémin, Sylvain (2022). Theoretical Predictions on the Effects of Self-Fertilisation on Speciation. Full text in Research Archive
• Marie-Orleach, Lucas; Brochmann, Christian & Glémin, Sylvain (2022). Mating System and Speciation: Accumulation of Genetic Incompatibilities in Allopatry. Full text in Research Archive
• Marie-Orleach, Lucas; Brochmann, Christian & Glémin, Sylvain (2021). Mating System and Speciation – Accumulation of Genetic Incompatibilities in Allopatry. Full text in Research Archive
• Marie-Orleach, Lucas (2020). Transitions between Sexual Systems: Understanding the Mechanisms of, and Pathways between, Dioecy, Hermaphroditism and Other Sexual Systems. The Quarterly review of biology. ISSN 0033-5770. 95(1), p. 86–86. Full text in Research Archive
• Marie-Orleach, Lucas; Brochmann, Christian & Glémin, Sylvain (2020). How fast does the "speciation clock" tick in selfing versus outcrossing lineages? Full text in Research Archive
• Marie-Orleach, Lucas (2019). Sexual selection, indirect genetic effects and speciation. Full text in Research Archive
• Marie-Orleach, Lucas (2019). Sexual selection, indirect genetic effects and speciation. Full text in Research Archive

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