The opposing effects of genetic drift and Haldane's sieve on floral‐morph frequencies in tristylous metapopulations

Abstract

Summary Tristyly is a genetic floral polymorphism in which three floral morphs are maintained at equal frequencies by negative frequency‐dependent selection on alleles at two interacting loci. Because dominant alleles at these loci are maintained at a lower frequency than their recessive counterparts, they are more likely to be lost by founder events and genetic drift.Here we examine the hypothesis that dominant alleles under negative frequency‐dependent selection should also be more likely to re‐invade populations than recessive alleles, due to Haldane's Sieve, because recessive alleles not expressed in a heterozygote state cannot benefit from positive selection when rare.We used computer simulations of tristylous metapopulations to verify that Haldane's Sieve acting on migrants into occupied demes can indeed reverse the bias in allele frequencies expected for small single tristylous populations, particularly in situations of rapid population growth following colonisation. This effect is manifest both locally and at the metapopulation level.Our study illustrates the potential effect of Haldane's Sieve in the novel context of an iconic plant sexual‐system polymorphism under the influence of metapopulation dynamics.

Population biology and phenology of the colour polymorphic damselfly Ischnura elegans at its southern range limit in Cyprus

“…While dominant alleles under negative frequency‐dependent selection are more likely to be lost by genetic drift, they also re‐invade populations more easily due to Haldane's Sieve, the expectation that a weakly advantageous mutation will increase more rapidly in frequency if dominant (Haldane, 1924; Pannell et al ., 2005). Haldane's Sieve acting on migrants might thus contribute to the maintenance of the dominant A‐allele at a regional scale (Roux & Pannell, 2019).…”

The ecology, evolution, and genetics of plant reproductive systems

“…1215–1228) have used a similar modelling approach to show that temporal (flowering time) and spatial structuring of gene pools can act synergistically to facilitate adaptation at small scales. Simulation modeling was used by Roux & Pannell (, in this issue pp. 1229–1240) to explore the interaction between migration frequency‐dependent selection and drift in metapopulations, and their study reveals that a process akin to Haldane's sieve (Haldane, ) can counteract the tendency for lower frequency alleles that underlie phenotypes in tristylous taxa to be lost, reminding us that the genetic control of plant reproductive systems cannot be ignored in analytical approaches.…”

QTL analysis of floral morphology polymorphisms betweenGilia yorkiiandG. capitata

“…color and size of petals, anther and style lengths, and throat length) makes important contributions to reproductive isolation and speciation (Rieseberg et al 2006). Divergent floral morphologies can arise from pollinator-driven selection (Wessinger et al 2014;Brothers et al 2013;Chen et al 2020;Campitelli et al 2018;Kostyun et al 2019), breeding system incompatibilities (Kostyun et al 2019;Roux and Pannell 2019;Mertens et al 2018;Eckert et al 1996;Goodwillie et al 2006), and random genetic drift (Roux and Pannell 2019;Tremblay and Ackerman 2001;Yoshida et al 2008). Despite the central role floral morphology plays in plant evolution and taxonomy, surprisingly little is known about the genetic mechanisms that underlie the morphological evolution of flowers.…”

“…2019), breeding system incompatibilities (Kostyun et al . 2019; Roux and Pannell 2019; Mertens et al . 2018; Eckert et al .…”

“…1996; Goodwillie et al . 2006), and random genetic drift (Roux and Pannell 2019; Tremblay and Ackerman 2001; Yoshida et al . 2008).…”