Establishing a protected area can restore honeybee population size and genetic diversity

Monitoring population genetic diversity is a fundamental component of biodiversity conservation practices. Because of its intimate links with population demographic size and adaptive potential, diachronic analyses of genetic diversity can allow, in principle, to assess the putative impacts of both anthropogenic disturbance and conservation initiatives. Yet, while the genetic imprints of anthropogenic disturbances have been extensively investigated, much less use has been made of population genetic data to address the effect of conservation efforts. Here, using diachronic samples of wild honeybee Apis mellifera populations in southern Italy, we explore the use of population genetic data to address the genetic and demographic consequences of the establishment of a national park. We found a substantial difference in the demographic trend among the two diachronic samples. While the honeybee population was declining at the time of the national park establishment, estimates of the effective population size after thirty years indicated a 12-fold demographic expansion. Within the same time-frame, we observed a substantial increase of population genetic diversity parameters within the study area. Allelic richness increased from 3.38 to 4.69, the expected heterozygosity increased from 0.35, to 0.42, and the Fst between the two temporal samples was 0.05 (P < 0.01). Overall, these data support the beneficial effects of area-based conservation efforts on honeybee populations. Importantly, results from this study highlight the significance of genetic investigation on diachronic samples to reveal hidden demographic trends of natural populations, to meet conservation commitments and to assess their efficacy over time.