Repeated evolution and reversibility of self-fertilization in the volvocine green algae*
AffiliationUniv Arizona, Dept Ecol & Evolutionary Biol
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CitationHanschen, E. R., Herron, M. D., Wiens, J. J., Nozaki, H. and Michod, R. E. (2018), Repeated evolution and reversibility of self‐fertilization in the volvocine green algae. Evolution, 72: 386-398. doi:10.1111/evo.13394
Rights© 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.
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AbstractOutcrossing and self-fertilization are fundamental strategies of sexual reproduction, each with different evolutionary costs and benefits. Self-fertilization is thought to be an evolutionary dead-end strategy, beneficial in the short term but costly in the long term, resulting in self-fertilizing species that occupy only the tips of phylogenetic trees. Here, we use volvocine green algae to investigate the evolution of self-fertilization. We use ancestral-state reconstructions to show that self-fertilization has repeatedly evolved from outcrossing ancestors and that multiple reversals from selfing to outcrossing have occurred. We use three phylogenetic metrics to show that self-fertilization is not restricted to the tips of the phylogenetic tree, a finding inconsistent with the view of self-fertilization as a dead-end strategy. We also find no evidence for higher extinction rates or lower speciation rates in selfing lineages. We find that self-fertilizing species have significantly larger colonies than outcrossing species, suggesting the benefits of selfing may counteract the costs of increased size. We speculate that our macroevolutionary results on self-fertilization (i.e., non-tippy distribution, no decreased diversification rates) may be explained by the haploid-dominant life cycle that occurs in volvocine algae, which may alter the costs and benefits of selfing.
Note12 month embargo; published online: 14 November 2017
VersionFinal accepted manuscript
SponsorsNational Aeronautics and Space Administration [NNX13AH41G, NNX15AR33G]; National Institute of Health [GM084905]; National Science Foundation [MCB-1412395, DEB-1457701]; MEXT/JSPS KAKENHI [15K14590, 16H02518]