Population structure and gene flow among culvert roosts of the trawling bat, the large-footed Myotis Myotis macropus

With rates of urbanisation increasing globally, there is a pressing need to understand the population structure and genetic vulnerability of wildlife populations within urban environments. The large-footed myotis (Myotis macropus) is a trawling bat found roosting and breeding in concrete culverts under roads. Little is known about levels of gene flow among roosting colonies in an urban environment, and this vital to assessing impacts of roost disturbance and exclusions caused by road upgrades.

We used single nucleotide polymorphisms to study gene flow within and between culvert roosts, in peri-urban and urban landscapes. We found genetic differentiation between all roosts. Gene flow was moderate between peri-urban roosts and restricted between urban roosts. Moderate levels of relatedness between peri-urban roosts indicates M. macropus roosting in culverts are part of a larger, outward breeding population. Comparatively, the urban roosts in our study had more related pairs than the peri-urban roosts, indicating reduced gene flow in urban culvert roosts.

We found evidence of female philopatry with pairs of related females within roosts. Our results suggest M. macropus has a harem social structure and a promiscuous breeding system due to limited shared paternal ancestry. Female dispersal distances are less than 30 km and female biased gene flow is locally restricted. These findings suggest that disturbance to, or removal of, a culvert roost has the potential to be a significant impact to an urban population of M. macropus.