Identifying the fitness consequences of sex in complex natural environments

Abstract

In the natural world, sex prevails, despite its costs. Although much effort has been dedicated to identifying the intrinsic costs of sex (e.g., the cost of males), few studies have identified the ecological fitness consequences of sex. Furthermore, correlated biological traits that differ between sexuals and asexuals may alter these costs, or even render the typical costs of sex irrelevant. We conducted a large-scale, multisite, reciprocal transplant using multiple sexual and asexual genotypes of a native North American wildflower to show that sexual genotypes have reduced lifetime fitness, despite lower herbivory. We separated the effects of sex from those of hybridity, finding that overwinter survival is elevated in asexuals regardless of hybridity, but herbivores target hybrid asexuals more than nonhybrid asexual or sexual genotypes. Survival is lowest in homozygous sexual lineages, implicating inbreeding depression as a cost of sex. Our results show that the consequences of sex are shaped not just by sex itself, but by complex natural environments, correlated traits, and the identity and availability of mates.

Rapid local adaptation in both sexual and asexual invasive populations of monkeyflowers (Mimulusspp.)

“…Yet, the traditional view was that local adaptation has a greater importance in sexual populations with a long evolutionary history (i.e. those with a greater number of recombination events behind; Weissmann, 1889;Crow and Kimura, 1965;Maynard Smith, 1968;Burt, 2000;Rushworth et al, 2020). In contrast, clonal propagation has been considered to reduce the opportunities for local adaptation (Schon et al, 1998;Rouzine et al, 2003;Schiffels et al, 2011) despite this mechanism can theoretically occur through selection on genes or genotypes trait for plant invasions, and numerous invasive plant species combine both sexual and asexual modes of reproduction or are mostly asexual (Pyšek, 1997;Silvertown, 2008;Roiloa, 2019).…”

“…However, although an increasing number of studies have shown evolution at a contemporary scale in invasive plants with sexual (Lucek et al, 2004;Maron et al, 2004;Leger and Rice, 2007;Novy et al, 2013;Li et al, 2015;Bhattarai et al, 2017;Marchini et al, 2018) or mixed reproductive systems (Michel et al, 2004;Lambertini et al, 2010), field tests of local adaptation and phenotypic plasticity are rare for obligately asexual flowering plants (Mitchell and Whitney, 2018;Rushworth et al 2020).…”

“…The traits underlying the local adaptation of M. × robertsii in UK are yet to be fully identified, and thus populations of this species are an ideal target for further research on the mechanisms mediating rapid evolution in asexual species (see also Rushworth et al, 2020).…”

Seed type and origin‐dependent seedling emergence patterns in Danthonia californica, a species commonly used in grassland restoration

“…Cleistogamous seeds are difficult to remove manually, potentially contributing to their infrequent use in D. californica restoration (Hayes & Holl, 2011 ). Although mating system generally does not influence the degree of local adaptation across species (Hereford, 2010 ), many studies have shown different fitness and local adaptation patterns for conspecific seeds produced via different mating systems (Lovell et al, 2014 ; Rushworth et al, 2020 ; Schmitt & Gamble, 1990 ). However, discussion of the applied aspects of mating system‐dependent seed selection for restoration is relatively rare in the literature (Charlesworth, 2007 ; Coulter., 1914 ; Rushworth et al, 2020 ).…”

Rapid local adaptation in both sexual and asexual invasive populations of monkeyflowers (Mimulus spp.)

“…Yet, the traditional view was that local adaptation has a greater importance in sexual populations with a long evolutionary history (i.e. those with a greater number of recombination events behind; Weissmann, 1889;Crow and Kimura, 1965;Maynard Smith, 1968;Burt, 2000;Rushworth et al, 2020). In contrast, clonal propagation has been considered to reduce the opportunities for local adaptation (Schon et al, 1998;Rouzine et al, 2003;Schiffels et al, 2011) despite this mechanism can theoretically occur through selection on genes or genotypes trait for plant invasions, and numerous invasive plant species combine both sexual and asexual modes of reproduction or are mostly asexual (Pyšek, 1997;Silvertown, 2008;Roiloa, 2019).…”