Repeated evolution and reversibility of self-fertilization in the volvocine green algae*

Erik R. Hanschen, Matthew D. Herron, John J. Wiens, Hisayoshi Nozaki, Richard E. Michod

Research output: Contribution to journalArticle

10 Scopus citations

Abstract

Outcrossing 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.

Original languageEnglish (US)
Pages (from-to)386-398
Number of pages13
JournalEvolution
Volume72
Issue number2
DOIs
StatePublished - Feb 1 2018

Keywords

  • Haploid
  • phylogenetics
  • self-fertilization
  • sex
  • sexual reproduction
  • volvocine green algae

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Ecology, Evolution, Behavior and Systematics
  • Genetics

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