Sexual selection, sexual conflict and the evolution of ageing and life span

Abstract

Summary 1.Classic evolutionary models interpret ageing as a cost of reproduction, but evolutionary research has thus far largely neglected the conceptual links between the evolution of ageing and a key mode of selection on male and female reproductive strategies -sexual selection and sexual conflict. 2. We synthesize ideas and evidence linking sex and ageing, and make the case that a focus on this fascinating problem will ultimately lead to a more complete understanding of both the evolution of ageing and the evolution of sexual strategies. 3. The primary and secondary differentiation of male and female reproductive strategies is expected to produce sex-specific optima for traits that affect longevity and ageing rate, often favouring a 'live fast, die young' strategy in males, relative to females, although numerous exceptions to this pattern are observed and sex-differences in ageing rate, in particular, remain poorly understood. 4. Conversely, environmental factors that influence life expectancy or ageing rate can thereby determine the magnitude or even sign of sexual selection. 5. Sexual conflict is expected to displace the sexes from their sex-specific life-history optima through sexually antagonistic interactions, as well as sex-specific selection on loci expressed in both sexes. 6. Despite the availability of interesting and testable hypotheses linking sexual selection and ageing, relevant empirical studies are remarkably sparse, and the complex relation between sex, mortality rate and ageing remains poorly understood.

Ejaculate economics: an experimental test in a moth

“…This phenomenon may be attributed to the elevated reproductive expenditure [15] or physical stress caused by male rivals via interfering with the mating pairs. However, unlike many other insect orders lepidopteran adults are not aggressive [23].…”

“…Empirical studies reveal that elevated reproductive expenditure is associated with accelerated ageing and reduced lifespan [15]. For example, male investment in reproduction may be made at the expense of longevity and future reproduction [16,17].…”

Reproductive costs in terrestrial male vertebrates: insights from bird studies

“…effort in wild males than females [7]. Also, while it has become an accepted notion that reproduction is costly for males as well [8][9][10], studies dealing with costs of reproduction in males are often rooted in the theory of sexual selection and therefore refer to the cost of producing or maintaining sexual traits on future survival [8] (see [11] for a recent review on the relationship between strength of sexual selection and age-specific survival patterns across vertebrates). Investigating reproductive costs in males specifically through the covariations between life-history traits (also called direct fitness traits sensu Roff [4], i.e.…”

Sexes suffer from suboptimal lifespan because of genetic conflict in a seed beetle

“…Theory maintains that sex-specific selection will optimize the fundamental trade-off between lifespan and reproduction differently for males and females [4][5][6][7], leading to ubiquitous dimorphism in lifespan and ageing rates across the animal kingdom [8][9][10][11], including humans [12]. However, recent advances in evolutionary biology strongly suggest that such optimization can be hard to attain in sexually reproducing organisms owing to genetic conflicts within the genome.…”