Social organisation and population structure in the brown long-eared bat, Plecotus auritus
Previous ringing studies of the brown long-eared bat (Plecotus auritus) in Britain suggest adults of both sexes are associated with the same summer colonies for many years, with at least some natal roost philopatry in both sexes. Detected movements among colonies are negligible. The aim of this study was to use molecular genetic markers to determine the levels of genetic relatedness within a colony, the levels of gene flow among colonies and the mating system. Six polymorphic microsatellite loci were isolated from a P. auritus genomic DNA library, and used to screen 666 P. auritus individuals from 26 colonies in north east Scotland. Paternity exclusions established that approximately a third of allocated paternities involved males from the same summer colony, although many females mate with males from roosts within 5 to 10 km. No skew in male reproductive success was identified, probably due to the inability of males to defend females throughout their oestrus. Mean levels of relatedness among all colony members was low, due mainly to extra-colony mating and low reproductive skew. Genetic differentiation among roosts was also low; but significant, and genetic isolation by distance was identified across the study area. Two highly divergent mtDNA lineages were identified within the population, which diverged by 1.9% at the 12S rRNA gene, suggesting a historically large population. The observed distribution of mtDNA haplotypes in the population may reflect past fission and fusion events in P. auritus colonies. Results from nuclear DNA markers support the occurrence of natal philopatry in both sexes, and suggest that P. auritus summer colonies should be regarded as separate sub-populations. However, each colony is reliant on others close by for mating, and genes move throughout the population via a stepping stone model. This species is therefore vulnerable to colony destruction and habitat fragmentation.