Targeted vertebrate surveys enhance the faunal importance and improve explanatory models within the Eastern Arc Mountains of Kenya and Tanzania

Aim Detailed knowledge of species distributions, endemism patterns and threats is critical to site prioritization and conservation planning. However, data from biodiversity inventories are still limited, especially for tropical forests, and even well recognized hotspots remain understudied. We provide an example of how updated knowledge on species occurrence from strategically directed biodiversity surveys can change knowledge on perceived biodiversity importance, and facilitate understanding diversity patterns and the delivery of conservation recommendations. Location Eastern Arc Mountains (EAM), Kenya and Tanzania. Methods We surveyed amphibians, reptiles, birds and mammals during 2005– 2009, targeting mountain blocks that had been poorly surveyed or unsurveyed by the early Noughties. We combined new and old data to produce a database of species presence by mountain block spanning four decades of research. Species richness is regressed against survey effort, funding, ecological and human disturbance factors to analyse the best predictors of vertebrate richness across mountain blocks. Similarity among species assemblages among blocks is analysed using dissimilarity analysis. Results New surveys raised the number of endemic and regional endemic vertebrates by 24% (from 170 to 211 species), including 27 new species of which 23 are amphibians and reptiles. Vertebrate richness is best explained by forest area, but rainfall is also important, especially for amphibians and reptiles. Forest elevational range is important for mammals and for block-endemic birds. Funding explains 19% of the variation in total species richness, while survey effort generally explains < 10% of variance. Cluster analysis shows that species assemblages are partitioned by geographical proximity among mountain blocks. Main conclusions The biological value of the EAM has been underestimated, and strategic surveys are important even in well-recognized hotspots. The exceptional and global importance of these mountains for endemic vertebrates is highlighted, supporting the development of a network of Nature Reserves and the proposed inclusion within UNESCO’s natural World Heritage Sites.