title: Increased diversification rates follow shifts to bisexuality in liverworts.
abstract: Shifts in sexual systems are one of the key drivers of species diversification. In contrast to angiosperms, unisexuality prevails in bryophytes. Here, we test the hypotheses that bisexuality evolved from an ancestral unisexual condition and is a key innovation in liverworts. We investigate whether shifts in sexual systems influence diversification using hidden state speciation and extinction analysis (HiSSE). This new method compares the effects of the variable of interest to the best-fitting latent variable, yielding robust and conservative tests. We find that the transitions in sexual systems are significantly biased toward unisexuality, even though bisexuality is coupled with increased diversification. Sexual systems are strongly conserved deep within the liverwort tree but become much more labile toward the present. Bisexuality appears to be a key innovation in liverworts. Its effects on diversification are presumably mediated by the interplay of high fertilization rates, massive spore production and long-distance dispersal, which may separately or together have facilitated liverwort speciation, suppressed their extinction, or both. Importantly, shifts in liverwort sexual systems have the opposite effect when compared to angiosperms, leading to contrasting diversification patterns between the two groups. The high prevalence of unisexuality among liverworts suggests, however, a strong selection for sexual dimorphism.
authors.affiliation: Department of Ecology, Environment and Plant Sciences, Science for Life Laboratory, Stockholm University, Stockholm, 10691, Sweden.|Department of Conservation Biology and Evolution, Institute of Botany, University of Liège, Liège, 4000, Belgium.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Laenen
authors.affiliation: Center for Macroecology, Evolution, and Climate, Natural History Museum of Denmark, Universitetsparken 15, DK 2100, Copenhagen, Denmark.|Department of Ecology, Charles University, Vinicna 7, Prague 2, 12844, Czech Republic.|Center for Theoretical Study, Charles University and Academy of Sciences of the Czech Republic, Jilska 1, Prague 1, 11000, Czech Republic.
authors.forename: Antonin
authors.initials: A
authors.lastname: Machac
authors.affiliation: Département Systématique et Evolution, Muséum National d'Histoire Naturelle, Paris, 75005, France.
authors.forename: S Robbert
authors.initials: SR
authors.lastname: Gradstein
authors.affiliation: Department of Biology, Duke University, Durham, NC, 27708, USA.
authors.forename: Blanka
authors.initials: B
authors.lastname: Shaw
authors.affiliation: Department of Conservation Biology and Evolution, Institute of Botany, University of Liège, Liège, 4000, Belgium.
authors.forename: Jairo
authors.initials: J
authors.lastname: Patiño
authors.affiliation: Department of Conservation Biology and Evolution, Institute of Botany, University of Liège, Liège, 4000, Belgium.|Department of Zoology, Naturhistoriska Riksmuseet, Stockholm, 10405, Sweden.
authors.forename: Aurélie
authors.initials: A
authors.lastname: Désamoré
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, 06269, USA.
authors.forename: Bernard
authors.initials: B
authors.lastname: Goffinet
authors.affiliation: Centro de Ciências do Mar (CCMAR), Universidade do Algarve, Campus de Gambelas, Faro, 8005-139, Portugal.
authors.forename: Cymon J
authors.initials: CJ
authors.lastname: Cox
authors.affiliation: Department of Biology, Duke University, Durham, NC, 27708, USA.
authors.forename: A Jonathan
authors.initials: AJ
authors.lastname: Shaw
authors.affiliation: Department of Conservation Biology and Evolution, Institute of Botany, University of Liège, Liège, 4000, Belgium.
authors.forename: Alain
authors.initials: A
authors.lastname: Vanderpoorten
mesh_terms: D044822:Biodiversity; D053476:Extinction, Biological; D049810:Genetic Speciation; D035926:Hepatophyta / Q000502:physiology*; D010802:Phylogeny; D013223:Statistics as Topic
keywords: Baker's law; dispersal; diversification; hidden state speciation and extinction analysis (HiSSE); liverworts; sexual systems