Genetic vulnerability of a remnant ant population

Ants are ecologically important species in many environments forming a big proportion of the total animal biomass. However, their special features such as sociality and complementary sex-determination system have received little attention in conservation discussions. We examined the social and genetic structure of the hairy wood ant Formica lugubris in Ireland to evaluate factors relevant to the vulnerability of small, isolated wood ant populations. We also clarified the conservation status of the species in Ireland. Our results showed that the populations are mainly monogynous (one queen per nest). Consequently the effective population size is very low (<100 individuals) in Ireland. We found extremely little genetic variation, signs of inbreeding and inbreeding depression, which can be a consequence of the small effective population size and of the restricted gene flow due to strong isolation of populations. Putatively high genetic diversity at the sex-determining locus can reflect a larger population in the past. The study shows that even though the population may seem stable because of the long life span of queen ants, sociality can impact species conservation by keeping the effective population size small. According to our results, the hairy wood ant can be considered native to Ireland. Hence it needs urgent protection and the genetic issues need to be considered in the future management strategies.