The consequences of sexual selection in well-adapted and maladapted populations of bean beetles†

Abstract

Whether sexual selection generally promotes or impedes population persistence remains an open question. Intralocus sexual conflict (IaSC) can render sexual selection in males detrimental to the population by increasing the frequency of alleles with positive effects on male reproductive success but negative effects on female fecundity. Recent modeling based on fitness landscape theory, however, indicates that the relative impact of IaSC may be reduced in maladapted populations and that sexual selection therefore might promote adaptation when it is most needed. Here, we test this prediction using bean beetles that had undergone 80 generations of experimental evolution on two alternative host plants. We isolated and assessed the effect of maladaptation on sex-specific strengths of selection and IaSC by cross-rearing the two experimental evolution regimes on the alternative hosts and estimating within-population genetic (co)variance for fitness in males and females. Two key predictions were upheld: males generally experienced stronger selection compared to females and maladaptation increased selection in females. However, maladaptation consistently decreased male-bias in the strength of selection and IaSC was not reduced in maladapted populations. These findings imply that sexual selection can be disrupted in stressful environmental conditions, thus reducing one of the potential benefits of sexual reproduction in maladapted populations.

Cross-sex genetic correlations for fitness and fitness components: Connecting theoretical predictions to empirical patterns

“…; Connallon and Hall ; but see Holman and Jacomb ; Martinossi‐Allibert et al. ), then should typically increase following environmental change. These consequences of environmental change for can be further modified by environmentally induced changes in the expression of quantitative genetic variation in addition to changes in selection.…”

“…; Han and Dingemanse ; Holman and Jacomb ; Martinossi‐Allibert et al. ; reviewed in Connallon and Hall ). The process of adaptation tends to bring both sexes closer to their optima, while simultaneously increasing sex differences in the orientation of directional selection (see Lande ; Connallon and Clark ; Connallon and Hall ; in the context of our model, adaptation is expected to increase θ and decrease and ).…”

Male-limited secondary sexual trait interacts with environment in determining female fitness

“…; Martinossi‐Allibert et al. ). This suggests that under natural conditions, characterized by environmental fluctuations, the role of sexually antagonistic genetic variation may be less pronounced than has been suggested by studies of populations in stable laboratory conditions (Long et al.…”

Digest: Sexual selection and conflict in a novel environment*

“…In this issue, Martinossi‐Allibert et al. () used an experimental evolution approach to quantify sexual conflict in bean beetles ( Acanthoscelides obtectus ) after an environmental change. First, the researchers created replicated lineages of bean beetles that were adapted to different plant hosts: chickpeas or white beans.…”

“…Martinossi‐Allibert et al. () note that male breeding success depends not only on abiotic conditions, but also the frequencies of other male genotypes (i.e., sexual competitors). They also point out that differences in female mate choice might exist between the two environments.…”