The evolution of male mate choice and female ornamentation: a review of mathematical models

Abstract

The evolution of male preferences and of female ornaments in species with traditional sex roles (i.e., polygyny) have been highlighted as areas in need of more active research by an accumulation of recent findings. The theoretical literature on these topics is relatively small and has centered on the evolution of male choice. Mathematical models have emphasized that, under polygyny, the evolution of male preferences faces much greater competition costs than does the evolution of female preferences. We discuss ways in which costly male choice can nonetheless evolve, via (1) direct selection that favors preferences, primarily through mating with highly fecund females, (2) mechanisms that rely on indirect selection, which weakly counters competitive costs of male preferences, and (3) genetic constraints, primarily in the form of pleiotropy of male and female preferences and traits. We also review a variety of mathematical models that have elucidated how costs to male preferences can be avoided. Finally, we turn our attention to the relatively scant theoretical literature on the effects of male mate choice on the evolution of female traits. We emphasize the finding that the presence of male preferences cannot be assumed to lead to the evolution of female ornaments during polygyny, and point out situations where models have elucidated ways in which female ornaments can nevertheless evolve.

Sexual selection, phenotypic plasticity and female reproductive output

“…What effect do sexually selected female traits have on mean female LRS? Clearly, mean female LRS must decline if there is any fitness tradeoff with naturally selected traits [161]. If females simply used a lottery rather than expended resources on competition to determine contested breeding opportunities, then the 'winning' female could invest more in reproduction.…”

“…To our knowledge, the circumstances where condition-dependence of female sexually selected traits elevates mean female LRS have not been formally modelled. We refer the reader to [161] for an extensive review of female ornament evolution. Female plasticity is mainly studied by asking how it affects male-imposed costs, or how it allows a female to choose males that increase her LRS or the fitness of her offspring.…”

On the logic of Fisherian sexual selection

“…The situation for haplodiploid species is the same as the case where both the preference and trait are Xlinked, with the additional point that the preference and trait loci can lie on separate chromosomes in haplodiploids-an important point, given that only the cis channel operates in this case, so that free recombination between the preference and trait loci (in females) is very helpful. Finally, we have considered the case of female mating preferences for male traits, but all of our results apply, mutatis mutandis, to male mating preferences for female traits, which are now recognized to play an important role in many systems (Edward & Chapman 2011, Fitzpatrick & Servedio 2018. The results for autosomal traits and preferences are the same as those for female choice, while the statements above for XX/XY and ZW/ZZ species reverse.…”

Information content of cheek and lip colour in relation to the timing of ovulation in women

“…The differences in red skin traits (face, lips, 229 and sexual skin) and signalling functions probably result from the different socio-230 environmental constraints on mating across species. Concealing the reproductive status may 231 have evolved in species facing higher male monopolization or pair-bonding, lower intra-232 sexual competition, and higher costs on signalling; while higher infanticide risks and intra-233 sexual competition, limited mating opportunities, and lower costs on signalling may have 234 favoured exaggerated or multimodal signalling [42,43]. However, these proposed effects do 235 not appear to fully explain the inter-species differences observed in female red skin colour 236 functions, as species with similar socio-ecology express traits that may be involved in either 237 ovulatory signalling or concealing (e.g.…”