Dispersal and Inbreeding Avoidance

Abstract

Using a game-theoretical approach, we investigate the dispersal patterns expected if inbreeding avoidance were the only reason for dispersal. The evolutionary outcome is always complete philopatry by one sex. The rate of dispersal by the other sex depends on patch size and mating system, as well as inbreeding and dispersal costs. If such costs are sex independent, then two stable equilibria coexist (male or female philopatry), with symmetric domains of attraction. Which sex disperses is determined entirely by history, genetic drift, and gene flow. An asymmetry in costs makes one domain of attraction extend at the expense of the other. In such a case, the dispersing sex might also be, paradoxically, the one that incurs the higher dispersal costs. As asymmetry increases, one equilibrium eventually disappears, which may result in a sudden evolutionary shift in the identity of the dispersing sex. Our results underline the necessity to control for phylogenetic relationships (e.g., through the use of independent-comparisons methods) when investigating empirical trends in dispersal. Our model also makes quantitative predictions on the rate of dispersal by the dispersing sex and suggests that inbreeding avoidance may only rarely be the sole reason for dispersal.

Genetics of dispersal

“…Comins, Hamilton & May, 1980;Hastings, 1983;Levin, Cohen & Hastings, 1984) and inbreeding depression (e.g. Motro, 1991;Gandon, 1999;Perrin & Mazalov, 1999). There is now an increasing number of models that explore the evolution of more-complex emigration rules that may depend, for example, on environmental conditions, local density of conspecifics (McPeek & Holt, 1992;Travis, Murrell & Dytham, 1999;Poethke & Hovestadt, 2002;Kun & Scheuring, 2006), and local density of prey/parasites/predators (Travis et al, 2013a;Iritani & Iwasa, 2014).…”

A comparative approach to testing hypotheses for the evolution of sex‐biased dispersal in bean beetles

“…First, costs of inbreeding can select for dispersal as a strategy to avoid mating with kin and its detrimental fitness effects due to the expression of deleterious alleles (Gandon 1999; Perrin and Mazalov 1999; Roze and Rousset 2005). This mechanism of inbreeding avoidance requires only that one sex disperse while the other may remain philopatric; in the absence of sex‐specific costs of inbreeding, dispersal bias in favor of either females or males is equally likely (Perrin and Mazalov 1999). As the negative fitness effects of inbreeding become stronger, so should selection for sex‐biased dispersal as an inbreeding avoidance strategy.…”

“…The inbreeding avoidance and kin competition hypotheses are not mutually exclusive. While inbreeding avoidance, alone, is not expected to select for a particular direction of sex bias in dispersal, it may amplify selection in the direction set by kin competition (Perrin and Mazalov 1999, 2000). …”

“…To our knowledge, quantitative relationships between sex‐biased dispersal and inbreeding or kin competition have not been previously explored in a comparative context. Furthermore, most existing comparative studies do not employ appropriate phylogenetic controls, which is necessary to quantify variation in sex‐biased dispersal across taxa (Perrin and Mazalov 1999; Handley and Perrin 2007). For example, the prevalence of female‐biased dispersal in birds could be more a reflection of shared phylogenetic constraint than of shared selective pressures related to mating system.…”

“…First, we predicted that taxa that suffer greater costs of inbreeding should exhibit greater sex bias in dispersal. Because inbreeding alone does not select for a direction of dispersal bias in the absence of sex‐specific costs (Perrin and Mazalov 1999), we examined the relationship between inbreeding depression and the absolute value of dispersal bias (bias in either direction). Second, we predicted that taxa with stronger kin competition should exhibit greater bias in dispersal.…”