The relative importance of reproductive assurance and automatic selection as hypotheses for the evolution of self-fertilization

Abstract

The transmission advantage and reproductive assurance ideas describe components of gene transmission that favour selfing. Future work should move beyond their dichotomous presentation and focus upon understanding whether selection through pollen, seed or both explains the spread of selfing-rate modifiers in plant populations.

The demography and population genomics of evolutionary transitions to self-fertilization in plants

“…Our survey results also indicate that, as might be expected, the reduction of diversity in selfing populations in the early stages of the transition was generally less compared with older lineages (figure 3b). Although the age estimates of selfing lineages are highly dependent on assumptions about mutation rates and generation times, the populations with the strongest reductions in genetic diversity do appear to be among the most highly diverged and show the most extreme changes in floral morphology [6]. These results are consistent with predictions from linked selection, and/or if older selfing lineages with high selfing rates have experienced recurrent bottlenecks and reduced gene flow.…”

“…Although small-effect modifiers are reported in some systems, the breakdown of selfincompatibility and floral modifications promoting selfing can involve genes of large effect (see below). Second, subsequent gene flow from outcrossing populations following the shift to selfing could erode an initial signal of a bottleneck during the transition to selfing [6]. Third, additional factors during the origin of selfing other than bottlenecks are known to reduce diversity in selfing relative to outcrossing populations [10], as we explore in detail later in this article.…”

“…The frequency with which selfing originates provides opportunities for identifying convergent patterns, and the mechanisms and consequences of this transition. Accordingly, efforts to understand how and why selfing evolves has had a long and venerable history, beginning with the early naturalists, including Charles Darwin, George Henslow and Hermann Mü ller (reviewed by Lloyd [4]), and continuing today using diverse comparative, experimental and genomic approaches [5][6][7]. In addition, a rich body of theory (reviewed by Goodwillie et al [8]) has developed on the selective mechanisms governing mating system variation and the genetic and evolutionary consequences of transitions to selfing.…”

Mixed Mating in Homostylous Species: Genetic and Experimental Evidence from an Alpine Plant with Variable Herkogamy,Primula halleri

“…Its occurrence in self-compatible, monomorphic (i.e., homostylous) primrose species that evolved from obligately outcrossing, heterostylous ancestors (Mast et al 2006;de Vos et al 2014ade Vos et al , 2014b) is therefore enigmatic. The loss of traits that enforce outcrossing is thought to be favored in environmental conditions where outcrossing opportunities are limited due to mate limitation and/or pollinator limitation, so that autonomous selfing may provide reproductive assurance (Eckert et al 2006;Busch and Delph 2012). …”

Evolutionary perspectives on clonal reproduction in vertebrate animals

“…From such mixed-mating taxa, several leading hypotheses for the adaptive significance of selfing (and/or for the evolution of selfing from outcrossing) have been advanced (96). For example, according to Baker (97,98), the fertilization assurance that selfing automatically affords can be highly advantageous, especially in colonizing species or those that regularly exhibit long distance dispersal in lowdensity population settings.…”