Analysis of the diversity and distributional patterns of coleopteran families on a global scale

Invertebrates make up the majority of all living species on earth. Nevertheless, our understanding of the global distribution of terrestrial biodiversity and regional patterns therein has thus far been almost entirely based on vertebrate and vascular plant patterns. Here we try to provide some information on the global biogeography of the largest invertebrate order, the beetles (Coleoptera). We compile and analyse a database of beetle distributions, containing presence-absence data for 177 coleopteran families across 827 ecoregions. We map family richness and weighted endemism and find the highest values in the Neotropics and Southeast Asia, but also in the temperate northern hemisphere. Important centres of beetle family endemism include the western and southern parts of North America, Central America, temperate South America, Europe, South, Southeast and East Asia, and eastern Australia. A series of UPGMA cluster analyses were used to produce two global regionalisation maps. As analyses on the complete dataset failed to produce contiguous clusters, two sub-datasets were considered. The first one excluded widespread families and family-poor ecoregions, and the second was restricted to endemic-rich ecoregions. The clusters resulting from the first analysis are partly similar to vertebrate- and plant-based regionalisation schemes, with easily discernible and extensive Holarctic and Holotropical regions, but also include numerous smaller regions, Caledonian, southern African), with Australia split between a tropical and a temperate/subtropical part. New Zealand is not analysed in this reduced dataset, but clusters with New Caledonia in the endemic-rich analysis, where further interesting subdivisions emerge (mainly in East Asia and western North America). We discuss these patterns in the light of coleopteran dispersal and the habitat requirements predominant across the coleopteran phylogeny, while considering the age of beetle families.