Investigating transitions from biparental to uniparental reproduction during colonization

Uniparental reproduction has evolved from biparental reproduction many times in plants and animals. Uniparentally reproducing populations are disproportionately found in habitats that have only recently been colonized. The advantage of uniparental reproduction during the colonization of such habitats may promote its frequent evolution, with a uniparental individual able to reproduce in a novel environment without requiring a mate. Different mechanisms of uniparental reproduction have evolved, classified under self-fertilization and parthenogenesis. The relative abundance of self-fertilization and parthenogenesis varies substantially among taxa in nature. This variation may result from differences among taxa in their developmental biology or their evolutionary histories. We investigated the latter possibility by modeling transitions from biparental to uniparental reproduction during the colonization of novel environments. Using a diploid gene regulatory network model, we simulated events in which a uniparental individual dispersed from a source biparental population and colonized a novel environment differing from the source environment by a specified magnitude. Our simulation results confirmed the hypotheses that 1) mitotic parthenogens that lack segregation and crossing over achieve higher colonization success when environmental change is low because they do not experience inbreeding depression, and 2) self-fertilizers achieve higher colonization success when environmental change is drastic because segregation and crossing over produce greater genetic variation which improves adaptability. Our results help distinguish between likely and unlikely evolutionary paths from biparental to uniparental reproduction in taxa that have made these transitions frequently.