Data from: Genetic and phenotypic responses to habitat fragmentation in a European harvester ant

Habitat fragmentation threatens wildlife populations and may cause reduced
genetic variation, fitness, and even local extinction, but effects differ
across species. Here, we addressed effects of habitat fragmentation using
the harvester ant Messor structor, a habitat specialist in
natural xerothermic grassland, in 54 habitat islands of a fragmented 200
km² area in Austria analysing microsatellites, mitochondrial DNA,
infection with the endocellular bacterium Wolbachia, and morphology. We
found (a) pronounced genetic diversity and two mitochondrial lineages that
we infer to originate from separate glacial refugia.
(b) Wolbachia infection rates were high, but the two strains
detected, correlating with the mitochondrial lineages, do not seem to have
induced a reproductive barrier. (c) Habitat islands with fewer ant nests
had less allelic richness, and the ones with less allelic richness had
reduced heterozygosity, as measured by mean locus heterozygosity; this
indicated inbreeding. (d) Fluctuating asymmetry of workers, known to be
low in fit individuals, positively correlated with heterozygosity, as
measured by the interallelic distance of heterozygous loci; high levels of
this distance probably are due to the mixing of lineages, and facing such
a potential outbreeding depression, vulnerability for inbreeding may
increase. (e) Gyne mesosoma size in less connected habitat was smaller
than that of gynes in better connected habitat, indicating reduced flight
ability. Our work highlights the use of multiple approaches to evaluate
species responses to habitat fragmentation, showcasing the importance of
historical colonization and current habitat connectivity to the
maintenance of genetic and phenotypic diversity.