Abstract
Reports regarding the current state of biodiversity worldwide tell grim tales of anthropogenic environmental effects causing rapid decline in species abundances across the globe and extinction rates on par with those of our planet’s most devastating extinction events. Despite this, only a fraction of the Earth’s species have been discovered and formally described (“The Linnean Shortfall”), and knowledge is lacking regarding the distributional patterns of the species we do know about (“The Wallacean Shortfall”). Here, the Staphylinid beetle diversity patterns of the Afrotropics across the continent are explored and compared along the elevational gradients of selected mountains. Taxonomic Hill alpha and beta diversity is measured, and Redundancy Analysis (RDA) and Non-Metric Multidimensional Scaling (NMDS) are conducted on samples collected from Mt. Cameroon in West Africa and the Pare Mountains of the Eastern Arc in East Africa. The data from the younger, higher and less disturbed Mt. Cameroon suggest a monotonic decrease in alpha diversity with increasing elevation. The difference in elevation between sites is found to be the largest determinant of diversity, whereas distance between sites is less important. The Pare mountains are older, lower and highly fragmented. This is reflected in a lack of clear correlation between elevation and diversity, higher dissimilarity between samples from different slopes, as well as a much higher impact of distance between sites on beta diversity. The phylogenetic relationships within the genus Megarthrus are explored by Maximum Likelihood analyses of a dataset based on sequences of 10 nuclear single copy protein-coding genes, obtained with multiplex PCR followed by sequencing on the Oxford Nanopore MinION platform. Fourty-seven species of Proteininae, sampled globally, are included, and the phylogeny recovers all the 23 included species of Afrotropical Megarthrus as one shallow clade, suggesting single dispersal of the genus into Africa, followed by profuse diversification. Within the Afrotropical clade, there are several regional subclades, restricted to the Ethiopian highlands, and more widely distributed subclades composed of very closely related species occurring across the Afrotropical region. These results imply that Megarthrus might be better disperses than previously assumed. The genus Metopsia (represented by four species) is nested within Megarthrus, rendering the latter paraphyletic. Finally, one new species of Megarthrus from Mt. Cameroon is described, and M. kamerunensis Bernhauer, 1942 is redescribed.