This project is integrating field and genetic techniques to improve our understanding of the ecological and evolutionary processes driving population structure and persistence in the crocodiles of Central Africa. Combining information from independent genetic markers with radio telemetry data on crocodile movement and habitat use will allow us to differentiate between the effects of historic landscape features (e.g. river hydrology, mountain ranges) and contemporary, human-driven land cover change on the distribution and current status of slender-snouted crocodiles. In the face of rapid environmental change, research focusing on biodiversity can no longer afford to be narrow in scope. This study transcends this challenge by examining the conservation-relevant ecology and evolution of crocodiles at multiple spatial and temporal scales.
This project will contribute significantly to our understanding of the evolution of biodiversity in Central Africa. An increased understanding of the evolution of wild crocodilian populations will both facilitate management efforts and provide a unique realization of the interaction between historic landscape features (which were forming when modern crocodiles appear in the fossil record), relatively recent climatic cycles, and modern anthropogenic threats like overharvesting and habitat loss. Slender-snouted crocodiles are the least known crocodilian in the world and this study will finally enable management programs for it. This study is contributing significantly and immediately to the conservation of wildlife in Central Africa through capacity-building with local Gabonese students and facilitation of the development of new protected areas and management strategies for highly threatened crocodiles in Gabon.
Understanding how species respond to dynamic geologic, climatic and ecological processes is critical for continent-scale conservation planning. Evolutionary conservation offers a framework to consider evolutionary processes in conservation by prioritizing management action at and below the species level. Unfortunately, implementing evolutionary conservation is often hindered by insufficient knowledge of both species-specific and regional evolutionary processes, particularly where those species exist only in challenging geopolitical settings. Two such species are the slender-snouted crocodile (Mecistops cataphractus) – the least known crocodilian in the world – and the African dwarf crocodile (Osteolaemus tetraspis). To overcome this knowledge deficiency and plan for future species management, we investigated the interaction of regional abiotic processes and species ecology in shaping the phylogeographic histories of these sympatrically distributed African crocodiles using a comparative phylogeographic framework. Using a total evidence phylogenetic approach we uncovered previously undescribed Mecistops species isolated in the Upper Guinea and Congo biogeographic zones. The timing of lineage divergence for these taxa was congruent with Osteolaemus and African Crocodylus lineages and identified the Cameroon Volcanic Line as a significant biogeographic barrier. Within the Congolian biogeographic zone, we uncovered similar patterns of spatial genetic structure between Mecistops and Osteolaemus, with evidence for historically widespread and well-connected populations in both species. Varying degrees of genetic isolation between the Congo, Ogooué and coastal basins underscored the importance of interpreting regional biogeographic processes in light of ecological factors like associations with forest cover and species-specific habitat utilization. Finally, we demonstrated that both species underwent significant demographic declines related to major climatic events since the late Pleistocene from which they were unable to recover genetic diversity. This multi-scale research considerably expanded our understanding of the processes structuring crocodilian diversity across western Africa. The observed congruence of speciation pattern, spatial genetic structure, and demographic histories between these sympatric crocodilians supports the importance of regional processes like geographic vicariance and climate change despite divergent ecological profiles. In addition, these results highlight the critical role that systematics and phylogeography play in biodiversity conservation of West and Central African fauna, and draws attention to conservation concerns for two of the world’s least studied crocodilians.
