Genetic variability and population size covary positively across nine badgers ( Meles meles ) populations in France

How population size is related to genetic diversity is a long-standing debate in evolutionary ecology and conservation biology. Despite being theoretically expected, the positive relationships between these demographic and genetic components of the species’ ecology are not always found at both the inter- and the intra-specific levels. Numerous factors have been proposed to explain such a discrepancy including demographic, genetic, ecological, and methodological processes. Here, we investigated the link between the genetic diversity and the population size at the intra-specific level within nine badger ( Meles meles ) populations of similar area size, using both robust estimates of population size and genetic diversity indices obtained from neutral microsatellite loci. This allowed us to circumvent the main confounding factors likely hiding the positive relationship between population size and genetic diversity. As expected, we found that the larger the population size, the higher the genetic diversity, independent of the genetic diversity index used. The main implication of this result resides in the fact that low population size is associated with lowered genetic diversity, likely decreasing the adaptive potential of small populations and putting them at risk of an extinction vortex. It calls also for a joint demo-genetic study of badger populations, and more largely in carnivore populations, especially in a situation of rising over-exploitation such as the one suffered by the badger in the context of the bovine tuberculosis outbreak in Europe.