Preprint maps fine-scale maternal structure and high nuclear connectivity in French Geoffroy's bat populations

Researchers have characterised the genetic diversity and population structure of the Geoffroy's bat (Myotis emarginatus) across 18 maternity colonies in France, using a combined approach of 34 microsatellite markers and mitochondrial D-loop sequencing in 760 individuals. The preprint, posted to bioRxiv, reports a clear divergence between the signals provided by the two marker types.

Mitochondrial data — which track maternal lineages — revealed subtle but detectable regional structure, consistent with female philopatry: females tend to return to their birth colony to breed, carrying their maternal haplotype with them. A broader phylogeographic split was also detected between Western European and Greater Middle Eastern populations, suggesting historical isolation, likely during Pleistocene glacial periods.

By contrast, microsatellite data — which capture nuclear, biparentally inherited variation — showed high diversity and minimal structure across the sampled colonies. The authors interpret this as evidence of extensive male-mediated gene flow, with males dispersing widely between colonies and thereby homogenising nuclear diversity even as maternal lineages remain locally differentiated.

The Geoffroy's bat is classed as increasingly threatened by habitat alteration across much of its European range. The population genetic portrait provided by this study may assist conservation planning by identifying which colonies maintain distinct maternal lineages and how nuclear connectivity might buffer against local extinctions. As a preprint, the findings have not yet been peer reviewed.