Immune gene variability influences roe deer natal dispersal
Abstract
Dispersal is a key life-history trait governing the response of individuals, populations and species to changing environmental
conditions. In the context of global change, it is therefore essential to better understand the respective role of
condition-, phenotype- and genetic-dependent drivers of dispersal behaviour. Although the importance of immune function
and pathogen infestation in determining patterns of dispersal is increasingly recognised, no study to our knowledge
has yet investigated the influence of immune gene variability on dispersal behaviour. Here, we filled this knowledge gap
by assessing whether individual heterozygosity at five immune gene loci (one from the Major histocompatibility complex
and four from encoding Toll-like receptors) influences roe deer natal dispersal. We found that dispersal propensity was
affected by immune gene diversity, suggesting potential pathogen-mediated selection through over-dominance. However,
the direction of this effect differed between high and low quality individuals, suggesting that dispersal propensity is driven
by two different mechanisms. In support of the condition-dependent dispersal hypothesis, dispersal propensity increased
with increasing body mass and, among high quality individuals only (standardized body mass 18 kg), with increasing
immune gene diversity. However, among poor quality individuals, we observed the opposite pattern such that dispersal
propensity was higher for individuals with lower immune gene diversity. We suggest that these poor quality individuals
expressed an emergency dispersal tactic in an attempt to escape a heavily infested environment associated with poor fitness
prospects. Our results have potentially important consequences in terms of population genetics and demography, as well
as host–pathogen evolution.