Evol Ecol Res 19: 299-318 (2018)     Full PDF if your library subscribes.

On the rediscovery of Volvox perglobator (Volvocales, Chlorophyceae) and the evolution of outcrossing from self-fertilization

Erik R. Hanschen1,2,, Dinah R. Davison2, Patrick J. Ferris2 and Richard E. Michod2

1Division of Bioscience, Los Alamos National Laboratory, Los Alamos, New Mexico, USA and 2Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona, USA

Correspondence: E.R. Hanschen, Division of Bioscience, Los Alamos National Laboratory, Los Alamos, NM 87544, USA. email: hanschen@lanl.gov


Hypothesis: Genetic recombination underlies the frequent origins of self-fertilization and rare reversions to outcrossing.

Organisms: Volvox perglobator, Gonium pectorale, volvocine green algae.

Methods: We report the rediscovery of a volvocine alga, obligate outcrossing V. perglobator, including morphological characteristics and molecular phylogeny. We use ancestral-state reconstruction and phylogenetic simulation to demonstrate multiple transitions between self-fertilization and outcrossing. We sequence sex-determining genes in multiple volvocine algae.

Results: We find significant support for numerous origins of self-fertilization and multiple reversions to outcrossing. Volvox perglobator is one of these reversions to outcrossing. Combination of ancestrally sex-restricted and sex-determining genes into the same genotype correlates with the evolution of self-fertilization. Re-segregation of these same sex-determining loci into separate sexes correlates with the evolution of outcrossing. These results suggest that recombination underlies the evolutionary transitions between self-fertilization and outcrossing in the volvocine algae.

Keywords: homothallism, phylogenetics, reversion, self-fertilization, sexual reproduction, volvocine green algae.

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