On anisogamy and the evolution of ‘sex roles’

What do isogamous organisms teach us about sex and the two sexes?

“…While the authors of this article are in agreement with the notion that typical male and female sex roles derive from the initial sexual asymmetry of anisogamy as originally proposed by Darwin [90] and Bateman [91], we must note that this view has recently been the subject of debate (e.g. [93][94][95] against, [19,20,96,97] for). More generally, we would argue that most phenomena usually considered to be sexual selection and sexual conflict ultimately arise from anisogamy.…”

Causality and sex roles: prejudice against patterns? A reply to Ah-King

“…In our view, however, there appear to be prejudices at play when claiming [1][2][3] that mainstream models of sex roles that assign explanatory power to anisogamy are impossible to reconcile with cases of an allegedly 'unexpected' nature. This requires a wilful misunderstanding of recent theoretical models.…”

“…Ah-King [1] presents three arguments as to why being male or female (by definition, producing small or large gametes) does not underlie other sex differences in reproductive behaviour ('sex roles'). These are: that correlation does not equal causation; there is too much variation among and within species to talk about 'sex roles'; and that 'stochastic demographic' (SD) models by Gowaty and Hubbell [2,3] have more explanatory power than Schä rer et al [4] implied in a recent Opinion piece.…”

“…Although they identify important factors that affect choosiness (and, incidentally, competition for mates), such as mating latency and encounter probability with potential mates, these parameters are deliberately not linked to sex. If the models remain truly non-sex-specific, this implies that sex differences -which these models do not preclude [1] -will arise at random due to extrinsic ecological processes impacting one sex more strongly than the other. So we should find that in 50% of species (or populations) that show detectable sex differences, males are choosier/less competitive/ provide more post-mating parental care than females.…”

The Evolution of Sexually Antagonistic Phenotypes

“…This recent burst of research has not been without controversy, including early disagreements that often centered on defining the scope of the field and how to test its predictions (Chapman et al 2003a;Cordero and Eberhard 2003;Eberhard and Cordero 2003;Pizzari and Snook 2003;Arnqvist 2004;Eberhard 2004a;Schärer et al 2012;Ah-King 2013;Kokko et al 2013), as well as recent critiques evaluating the potential for gender bias in sexual conflict theory and focus (Green and Madjidian 2011;Madjidian and Green 2012;Perry and Rowe 2012a;Dougherty et al 2013). In recent years, a new era has begun as the field has matured, with studies considering implications for topics like aging (Promislow 2003;Bonduriansky et al 2008), population structure (Eldakar et al 2009b;Chang and Sih 2013), kin selection (Rankin 2011;Carazo et al 2014), human health (Badcock and Crespi 2008;Morrow and Connallon 2013), and extinction .…”