Fine-scale maternal structure and high nuclear connectivity in the French populations of the Geoffroy's Bat (Myotis emarginatus)

The Geoffroy's bat (Myotis emarginatus) is a sedentary species now at risk due to changing habitats. In a recent study, researchers examined the genetic diversity and population structure of 760 individuals from 18 French maternity colonies, utilizing 34 microsatellite markers and mitochondrial D-loop sequences.

By analyzing mitochondrial data, scientists detected subtle regional structure, consistent with female philopatry — the tendency of female bats to stay in their birthplace. This regional structure also revealed a broader phylogeographic split between populations in Western Europe and those in the Greater Middle East, indicating historical isolation between these regions.

Microsatellite analyses, however, demonstrated high nuclear diversity and minimal population structure within France. The gene flow among bats was predominantly male-mediated, with weak isolation by distance and kin clustering. This suggests that bats were able to move freely across the landscape, with limited genetic barriers.

Demographic inference further supported these findings, showing population stability consistent with the genetic results. Interestingly, the patterns of nuclear homogeneity and demographic stability observed in M. emarginatus populations align closely with those found in Rhinolophus ferrumequinum populations sampled at the same French maternity colonies. This suggests that reproductive aggregation, or the clustering of bats in specific maternity sites, can help maintain connectivity even in sedentary species.

Overall, the findings indicate that M. emarginatus functions as a largely connected population across France at the national scale. However, localized maternal lineages around key maternity sites suggest the presence of functional phylopatric units—geographically distinct populations that remain interbred but are adapted to specific local conditions. These findings highlight the importance of protecting these key sites to maintain the genetic diversity and adaptability of the species.

Future research using whole-genome studies could further refine conservation strategies by integrating fine-scale female philopatry with male-mediated connectivity, providing a more comprehensive understanding of the species' population dynamics.