The influence of persistent individual differences and age at maturity on effective population size

Abstract

Ratios of effective populations size, N e , to census population size, N, are used as a measure of genetic drift in populations. Several life-history parameters have been shown to affect these ratios, including mating system and age at sexual maturation. Using a stochastic matrix model, we examine how different levels of persistent individual differences in mating success among males may affect N e /N, and how this relates to generation time. Individual differences of this type are shown to cause a lower N e /N ratio than would be expected when mating is independent among seasons. Examining the way in which age at maturity affects N e /N, we find that both the direction and magnitude of the effect depends on the survival rate of juveniles in the population. In particular, when maturation is delayed, lowered juvenile survival causes higher levels of genetic drift. In addition, predicted shifts in N e /N with changing age at maturity are shown to be dependent on which of the commonly used definitions of census population size, N, is employed. Our results demonstrate that patterns of mating success, as well as juvenile survival probabilities, have substantial effects on rates of genetic drift.

Life-history traits and effective population size in species with overlapping generations revisited: the importance of adult mortality

“…Second, every year of delayed maturity increases generation length by 1 year (equation (8)) but by itself has no effect on the other parameters. Because N e is proportional to T (equation (1)), increasing age at maturity increases both N e and N e /N, as others have reported (Nunney, 1993;Waite and Parker, 1996;Lee et al, 2011). It is easy to show that the N e /N ratio can considerably exceed 1 when the age at maturity is substantially 41 (Figure 6, bottom; see also Waples et al 2013).…”

“…Constraints on litter size that can result in ϕ x o 1 also lead to only small increases in N e . On the other hand, if some individuals consistently are either good or bad at producing offspring across their lifetime, this will increase lifetime variance in reproductive success and reduce N e (Lee et al, 2011). This is difficult to track in natural populations but for some species it could significantly reduce the N e /N ratio.…”

Alternative splicing and the evolution of phenotypic novelty

“…Although compendia of effective population size data have developed substantially [93,94], there is still minimal overlap with the set of species for which comparative alternative splicing levels have been estimated. Taking adult body weight [95], average age at sexual maturity [96] and generation time [97] as proxies of effective population size [89] as well as 'effective information' (a value derived from principles of information theory as 'the minimal amount of genomic information needed to construct an organism') [98], the correlation of alternative splicing and cell-type number remains significant [62] (table 1 and electronic supplementary material, table S1). …”

Simple life-history traits explain key effective population size ratios across diverse taxa

“…Although elegantly simple in concept, N e is difficult to estimate in nature, particularly for iteroparous species that can reproduce in more than one season [2,3]. A number of studies have evaluated life-history factors that influence the ratio of N e to census size (N), with the goal of identifying rules-of-thumb that could be applied to species for which detailed demographic information is not available (nicely reviewed by Lee et al [4]). However, these theoretical analyses have generally made simplifying assumptions (e.g.…”