Examining diversity of terrestrial mammal communities across forest reserves in Sabah, Borneo

Tropical forest reserves have conservation value for terrestrial mammals and are threatened by anthropogenic pressures, especially conversion to other land-use types. To assess mammalian biodiversity of forest reserves in Sabah, Borneo, we used camera trapping data to estimate species richness, beta diversity, phylogenetic and functional diversity in nine forest reserves with different management classifications and backgrounds. Multiregional multispecies occupancy models (MSOM) were used to differentiate species occupancy in the reserves, and the estimates were transformed into biodiversity metrics. We found a significant difference in mammal composition within each forest reserve, with various functional and phylogenetic clustering or dispersion levels indicated by the standard effect of mean pairwise distances (SES MPD). Redundancy analysis (RDA) was used for both the observed data and MSOM estimates, modeling numerous environmental covariates and the forest reserves as random effects, finding that the forest reserve random effects were mainly responsible for structuring the mammal communities. Deramakot Forest Reserve was found to have overall high species richness, phylogenetic and functional diversity compared to other reserves. This reserve has been particularly successful at sustainable forest management and long-term forest certification, highlighting long-term conservation gains of sustainability programs for terrestrial mammalian diversity. Conversely, several reserves showed lower diversity scores overall than IUCN presumed extant species lists, highlighting local defaunation while still retaining high profile (critically endangered, endangered, and vulnerable) species. This study highlights the fragility of terrestrial mammal assemblages in forest reserves across the state and the need for mitigation, refaunation, and an integrated approach to forest management and biodiversity conservation to allow for comprehensive sustainable management programs to ensure long-term conservation.