The extent of undiscovered species in Southeast Asia

Southeast Asia has the highest rate of deforestation among all tropical regions in the world. Depending on the number of undiscovered species not yet known to science, a sizeable proportion of species may have gone extinct or will go extinct in the future without record. We compiled species datasets for eight taxa, each consisting of a list of native species and their description dates. Birds, legumes, mosquitoes, and mosses showed recent declines in species discovery rate. For these taxa, we estimated the total species richness by applying generalized linear models derived from theory. The number of undiscovered species in each taxon was calculated and the extent of undiscovered species among the taxa compared. Among these taxa that displayed a species discovery decline, the legumes had the highest extent of undiscovered species while the birds had the most complete species inventory. Although quantitative estimates of the number of undiscovered species for amphibians, freshwater fish, hawkmoths, and mammals could not be derived, the extent of undiscovered species is likely to be high as their recent discovery rates showed a continued increase. If these taxa are more or less representative of other Southeast Asian taxa, many species are likely to go extinct before ever being discovered by science under the current rates of habitat loss. We therefore urge the intensification of taxonomic and species discovery research in the taxa in which the extent of undiscovered species is relatively high, i.e., amphibians, freshwater fish, hawkmoths, mammals, and legumes.