Effect of Recurrent Selfing on Inbreeding Depression and Mating System Evolution in an Autopolyploid Plant

Abstract

Genome duplication resulting in polyploidy can have significant consequences for the evolution of mating systems. Most theory predicts that self-fertilization will be selectively favored in polyploids; however, many autopolyploids are outcrossing or mixedmating. Here, we examine the hypothesis that the evolution of selfing is restricted in autopolyploids because the genetic cost Inbreeding depression (δ), the reduced fitness of inbred offspring compared to outbred offspring, is a dominant selective force governing the evolution of mating systems (Lande and Schemske 1985;). The relative effect of selfing ranges widely among species, from having no fitness detriment to being nearly lethal, and is often negatively correlated with the population selfing rate (Agren and Schemske 1993;Latta and Ritland 1994a;Carr and Dudash 1996; Johnston and Schoen 1996;Dudash and Fenster 2001; Fishman 2001, reviewed by Husband and Schemske 1996;Goodwillie et al. 2005). This association reflects the role that inbreeding depression plays in restricting the evolution of selfing and affirms that inbreeding depression itself is not immutable but can evolve in concert with the mating system as recessive deleterious mutations are exposed by inbreeding and purged through selection (Lande and

On the widespread capacity for, and functional significance of, extreme inbreeding in ferns

“…Of the species for which we were able conclusively to determine ploidy level, relatively more polyploid than diploid species were capable of GS (82% of polyploids and only 54% of diploids, although this is based on only 11 species known to be polyploid; Table 1). In accord with the frequent suggestion in the literature that polyploids should be more tolerant of selfing than their diploid relatives (see, e.g., Stebbins, 1950;Grant, 1956;Soltis & Soltis, 1987;Haufler, 1989;Masuyama & Watano, 1990;Barringer, 2007;Ozimec & Husband, 2011), we did see higher average isolate potentials in polyploid compared with diploid species, but the difference did not reach statistical significance (Fig. 6b).…”

“…Future data collection efforts should focus on including groups of species with polyploid series and those found to be exclusively selfing, in order to improve our understanding of the relationship between ploidy level and selfing capacity in ferns. It has also been suggested that as polyploid genomes 'diploidize' following whole-genome duplication, and return to disomic inheritance and diploid expression patterns (Dodsworth et al, 2016), the fitness of selfed progeny may deteriorate and mating systems may also evolve, reverting to mixed mating or outcrossing strategies (Husband et al, 2008;Ozimec & Husband, 2011). Assessing mating systems in polyploids of known age could help to test this assertion.…”

Bottlenecks and inbreeding depression in autotetraploids

“…In response to population bottlenecks, tetraploids sometimes expressed higher inbreeding depression than is found in much larger populations at equilibrium (Fig. ; Ronfort ; Ozimec and Husband ). This likely occurred because of random selfing and mating between related individuals in small populations.…”

“…A persistent question has been whether polyploidy should be associated with increased rates of self‐fertilization in flowering plants (Stebbins ; Levin ; Lande and Schemske ; Ronfort ; Miller and Venable ; Mable ; Rausch and Morgan ; Barringer ; Robertson et al. ; Ozimec and Husband ). Two major hypotheses have been argued to support such an association.…”

Revisiting the Dioecy-Polyploidy Association: Alternate Pathways and Research Opportunities

“…In fireweed, synthetic neopolyploids have no detectable inbreeding depression [Husband et al, 2008], suggesting that selfing, not outcrossing, would be favored, unless the magnitude of inbreeding depression increases over successive generations of selfing [Miller and Venable, 2000]. The limited evidence available is in support for this possibility [Ozimec and Husband, 2011], but more study is needed.…”