Condition-dependence, genotype-by-environment interactions and the lek paradox

Abstract

The lek paradox states that maintaining genetic variation necessary for 'indirect benefit' models of female choice is difficult, and two interrelated solutions have been proposed. 'Genic capture' assumes condition-dependence of sexual traits, while genotype-by-environment interactions (GEIs) offer an additional way to maintain diversity. However, condition-dependence, particularly with GEIs, implies that environmental variation can blur the relationship between male displays and offspring fitness. These issues have been treated separately in the past. Here we combine them in a population genetic model, and show that predictions change not only in magnitude but also in direction when the timing of dispersal between environments relative to the life cycle is changed. GEIs can dramatically improve the evolution of costly female preferences, but also hamper it if much dispersal occurs between the life history stage where condition is determined and mating. This situation also arises if selection or mutation rates are too high. In general, our results highlight that when evaluating any mechanism promoted as a potential resolution of the lek paradox, it is not sufficient to focus on its effects on genetic variation. It also has to be assessed to what extent the proposed mechanism blurs the association between male attractiveness and offspring fitness; the net balance of these two effects can be positive or negative, and often strongly context-dependent.

Short-term change in male sexually selected traits and female mate preference in the guppy Poecilia reticulata

“…On the contrary, the intensity of female preference for bright male image was weak in July when conspicuous males were abundant. Some theoretical studies predict that there is plasticity in female mate preference, and females prefer rare male phenotypes (Kokko and Rankin 2006;Kokko and Heubel 2008). Results of this study seem to be consistent with these predictions.…”

“…However, some recent theoretical studies predict the plasticity in female preferences (Kokko and Rankin 2006;Kokko and Heubel 2008). If female preferences consistently favor some males having exaggerated ornaments over others, male ornaments will be exaggerated with a greater degree that are exposed to high predation risks or require more resources for production and maintenance of the traits.…”

Genotype × environment interaction is weaker in genitalia than in mating signals and body traits in Enchenopa treehoppers (Hemiptera: Membracidae)

“…Whilst G 9 E may contribute to the maintenance of genetic variation under selection (thus solving the ''lek paradox''), it also presents the problem that parent phenotypes may be poor predictors of offspring phenotypes and genotypes. This may weaken selection favouring mate choice on the basis of traits expressing G 9 E (Greenfield and Rodríguez 2004;Mills et al 2007;Bussière et al 2008;Kokko and Heubel 2008;Ingleby et al 2010). In light of this problem, our finding of relatively high heritabiliy and relatively weak G 9 E in genitalia suggests that the dynamics of sexual selection may be more stable for genitalia than for other types of sexual trait.…”

Mate choice for major histocompatibility complex genetic divergence as a bet-hedging strategy in the Atlantic salmon ( Salmo salar )

“…Under fluctuating environmental selection pressures, parental mating decisions should be to assure diversity within offspring, but will result in some proportion of offspring being maladapted to the future pathogen community (i.e. genetic bet-hedging; [63,64]). At the genomic level, it has been previously suggested that both natural and sexual selection may be driving the evolution of intermediate levels of diversity as a result of trade-offs between inbreeding Bet-hedging for MHC diversity M. L. Evans et al 383 and outbreeding depression [22,65 -67].…”