No Intra-Locus Sexual Conflict over Reproductive Fitness or Ageing in Field Crickets

Felix Zajitschek,Michael D Jennions,John Hunt,Susanne R.K Zajitschek,Robert Brooks

doi:10.1371/journal.pone.0000155

Felix Zajitschek, Michael D Jennions + Show 3 more

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https://doi.org/10.1371/journal.pone.0000155

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Abstract

Differences in the ways in which males and females maximize evolutionary fitness can lead to intra-locus sexual conflict in which genes delivering fitness benefits to one sex are costly when expressed in the other. Trade-offs between current reproductive effort and future reproduction and survival are fundamental to the evolutionary biology of ageing. This leads to the prediction that sex differences in the optimization of age-dependent reproductive effort may generate intra-locus sexual conflict over ageing rates. Here we test for intra-locus sexual conflict over age-dependent reproductive effort and longevity in the black field cricket, Teleogryllus commodus. Using a half-sib breeding design, we show that the most important components of male and female reproductive effort (male calling effort and the number of eggs laid by females) were positively genetically correlated, especially in early adulthood. However, the genetic relationships between longevity and reproductive effort were different for males and females, leading to low genetic covariation between male and female longevity. The apparent absence of intra-locus sexual conflict over ageing suggests that male and female longevity can evolve largely independently of one another.

Highlights

There is a growing appreciation that the conflict of evolutionary interests between males and females is a powerful and nearubiquitous evolutionary force [1,2,3]
This intra-locus sexual conflict [2] is mediated by the strength of the genetic correlation between the traits expressed in male and female, and constrains the evolution of sexual dimorphism [5,6]
Males showed a positive genetic correlation between early and late reproductive effort (Table 2, rA = 0.6260.22 s.e.), and both mean (Fig 2) and total calling effort were positively genetically correlated with male longevity (Table 2, mean calling effort – male longevity: rA = 0.4260.33 s.e., total calling effort – male longevity: rA = 0.5260.29 s.e.)

Summary

Introduction

There is a growing appreciation that the conflict of evolutionary interests between males and females is a powerful and nearubiquitous evolutionary force [1,2,3]. When selection favours different optimal trait values in males and females (i.e. selection is sex-specific), there is conflicting selection on the same body of genetic variation, depending on whether the genes are expressed in a male or a female. In polygenic traits, this intra-locus sexual conflict [2] is mediated by the strength of the genetic correlation between the traits expressed in male and female (i.e., the inter-sexual genetic correlation), and constrains the evolution of sexual dimorphism [5,6]

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Results

Conclusion