Coming of age in your local mating market: Just a numbers game?

Abstract

In their study of age-assortative mating, Woodman and colleagues thoroughly and concisely detail its behavioural determinants using datasets, astonishing in themselves, amassed from their decades-long studies of mute swans (Cygnus olor) and great tits (Parus major), species that are respectively longerand shorter-lived and occupying different segments of the slow/fast life-history continuum. Here, they show that positive age-assortative mating occurs through active, age-based mate selection in mute swans which play the long game, whereas in the shorter-lived great tit this is principally a passive byproduct of demographic processes. That great tits have relatively lower interannual survivorship means that newly recruited, young birds occupy a larger proportion of the breeding population in any given year than occurs in mute swans. The adaptive significance of age-assortative mating is yet to be determined, but the current study provides an exciting possibility for the role of selection on assortative mating generally in either promoting or constraining active mate selection and sexual dimorphism within and across the tree of life.

The ecology of ageing in wild societies: linking age structure and social behaviour in natural populations

“…Further, as well as influencing populationlevel breeding behaviour through individual age-specificity, population age structure might mediate mate choice by determining which individuals of a given age mate together if the age distribution is skewed towards specific age-cohorts. For example, recent work demonstrates that in species with high mortality rates, a large proportion of the population exists in a single age-cohort, and thus fluctuations in age structure largely determine variation in levels of age-assortative mating [93,188].…”