Historical Demography and Patterns of Connectivity Among Three Groups of Mandrills (Mandrillus sphinx) in Lopé National Park, Gabon

Citation

Weber A, Guibinga Mickala A, Lehmann D, Ntie S, Abernethy K, Mickala P & Anthony N (2026) Historical Demography and Patterns of Connectivity Among Three Groups of Mandrills (Mandrillus sphinx) in Lopé National Park, Gabon. International Journal of Primatology. https://doi.org/10.1007/s10764-026-00555-0

Abstract
Population size, demographic history, and dispersal all strongly influence genetic diversity. Species that lack diversity due to isolation, historical declines, or low effective population size may have reduced adaptive potential, so understanding population dynamics is important in protecting threatened primates. We assess demographic history and population connectivity of three groups of wild mandrills (Mandrillus sphinx) in Lopé National Park, Gabon, using microsatellite genotypes (n = 368) from noninvasively collected fecal samples. Specifically, we calculate multiple estimators of genetic divergence between the groups (Fst, G”st, Jost’s D), test for population structure using a Bayesian approach, estimate census and effective population size of the three groups combined, and use a coalescent model to assess the likelihood of a historical population bottleneck associated with past environmental change. We found no significant evidence of genetic divergence between the three groups, and three individuals were sampled in multiple groups, suggesting dispersal. We estimated a total census population size of 1,178–1,475 individuals (95% confidence interval [CI]) and effective population sizes of 156–234 or 322–631 (95% CI), depending on estimation method. Finally, we find no evidence of a genetic bottleneck occurring within the last ~20,000 years. The three mandrill groups therefore represent a diverse population that has experienced regular migrant exchange. Despite range-wide species-level declines, the Lopé mandrills appear to have maintained a steady population size. These results illustrate a positive outlook for mandrills where they are currently protected, although continued monitoring is essential for this species in the face of ongoing threats.

Keywords
Mandrill; Noninvasive genetics; Census size; Effective population size; Population structure; Demographic history