Regionalization of mammal assemblages in central African forests: determinants, sampling gaps, ongoing threats and conservation priorities

Aim: Central Africa shelters a diverse and iconic megafauna which is jeopardized by climate and land-uses changes and increased hunting-induced defaunation. Though being crucial for coordinating regional conservation actions, how species assemblages are spatially structured is still barely known. This study aims to fill this knowledge gap for mammals across central African forests.
Location: Tropical moist forests from Nigeria to the Albertine Rift
Methods: An extensive compilation of forest-dwelling mammal species lists was made from wildlife and bushmeat-related surveys across central Africa. To identify and delimit zoogeographic districts, separately for three orders well sampled, carnivores, primates and artiodactyls, a beta-diversity approach was implemented, enabling to cluster surveys with similar species composition despite various sampling methods and efforts. Random forest classification models were then used to identify the environmental determinants of the district’s distribution and to produce a continuous zoogeographic map needed to assess the conservation status of each district and their ongoing threats.
Results: While carnivores do not present a clear spatial structure within central African forests, our findings highlight the structuring role of rivers on both primate and artiodactyl assemblages’ distribution. We retained eight and six spatially congruent districts for primates and artiodactyls, respectively. These districts were shaped by the Ubangi/Congo River system, and the Cross and Sanaga Rivers, with a secondary role of insularity and precipitation identified for primates. Highly threatened districts were highlighted, especially in Nigeria and in the Democratic Republic of Congo, the latter including vast areas that are understudied and poorly represented in the protected area network.
Main conclusions: Beyond refining our understanding of the diversity and uniqueness of mammalian assemblages across central African forests, our map of zoogeographic districts has far-reaching implications for the conservation of highly threatened taxa, allowing to target species and areas of interest for further conservation and rewilding efforts.