Abstracts (first author)
Sex-biased dispersal, inbreeding and fitness in a social insect
Sex-biased dispersal may act as inbreeding avoidance strategy, yet data on natal dispersal and its effectiveness in reducing inbreeding in the wild are scarce. Perennial ant colonies offer a unique system to investigate the relationship between natal dispersal and inbreeding avoidance, as the dispersal and mating behavior of a queen during the short period of a mating flight will determine the genetic diversity among her offspring, for the entire life span of the incipient colony. We used pedigree information on parents of incipient and established colonies of the ant Formica exsecta, in order to examine the relationship between inbreeding, fitness, mating behavior, sex ratios, and patterns of natal dispersal. Dispersal was male-biased with male dispersal distances (ca. 150m) twice the length of those of queens (ca 60m), yet inbreeding was rife in the population. Neither multiple mating nor increasing dispersal distance by the queen reduced inbreeding among the offspring of her future colony. Queen homozygosity did not affect dispersal, but more homozygous queens had lower colony founding success, and were more incestuously mated themselves which may accentuate the negative effects of inbreeding. Inbreeding also affected resource allocation to the sexes, with inbred colonies producing smaller males, but not queens. We present first true estimates of natal dispersal distance in social insects. Our results emphasize that inbreeding may persist in absence of sib-mating, in species with supposedly population-wide panmictic mating behavior and sex-biased dispersal.