Co-limitation towards lower latitudes shapes global forest diversity gradients

The latitudinal diversity gradient (LDG) is one of the most recognized global patterns of species richness exhibited across a wide range of taxa. Numerous hypotheses have been proposed in the past two centuries to explain LDG, but rigorous tests of the drivers of LDGs have been limited by a lack of high-quality global species richness data. Here we produce a high-resolution (0.025° × 0.025°) map of local tree species richness using a global forest inventory database with individual tree information and local biophysical characteristics from ~1.3 million sample plots. We then quantify drivers of local tree species richness patterns across latitudes. Generally, annual mean temperature was a dominant predictor of tree species richness, which is most consistent with the metabolic theory of biodiversity (MTB). However, MTB underestimated LDG in the tropics, where high species richness was also moderated by topographic, soil and anthropogenic factors operating at local scales. Given that local landscape variables operate synergistically with bioclimatic factors in shaping the global LDG pattern, we suggest that MTB be extended to account for co-limitation by subordinate drivers

Assessing the spatiotemporal dynamics of endangered mammals through local ecological knowledge combined with direct evidence : the case of pangolins in Benin (West Africa)

Although pangolins are considered to be one of the most trafficked wild mammals in the world, their conservation status remains uncertain through most of their ranges, and notably in western Africa. Using local ecological knowledge in combination with direct occurrence evidence, we assessed the distribution and abundance of the white-bellied pangolin (Phataginus tricuspis) and the giant pangolin (Smutsia gigantea) in Benin over the last two decades (1998-2018). We organised focus groups with local hunters in 312 villages within sampling units of 25 km × 25 km covering the whole country. Participatory maps of past and current geographic ranges of pangolins combined with direct evidence (96 collected scales) suggested that the white-bellied pangolin had a wide distribution and reached higher latitudes than previously known, whereas the giant pangolin could be restricted to a single forest and has been absent from the northern part of the country over at least the last two decades. Local hunters perceived a significant decline of the white-bellied pangolin (range contraction = 31% in 20 years) and almost unanimously an extirpation of the giant pangolin (93%), the latter being restricted to the Alibori forest reserve (northern Benin). Protected areas were identified as the main potential occurrence zones for pangolins: 77 and 100% of the potential geographic ranges of the white-bellied and the giant pangolins, respectively, overlapped partially or totally with the protected area network of Benin. Using a generalized linear model, we showed that the probability of reporting recent observations of the white-bellied pangolin was significantly higher for villages near protected areas and distant from main roads. The forests perceived as having sustainable populations of white-bellied pangolins were the Lama Forest reserve (southern Benin) and the complex comprising Monts Kouffé - Wari Maro - Ouémé supérieur (central Benin), a view that was supported by the great number of direct occurrence evidence collected in those areas. Overall, our study highlights an important geographic range contraction of the white-bellied pangolin and a possible entire extirpation of the giant pangolin over the last two decades in Benin