Predictions of Mammal Diversity on Four Land Masses

Abstract

Knowledge about the number of living species is fundamental to the practice of conservation biology, but we are far from knowing the number of species even for relatively well‐known groups such as mammals. We analyzed a database that contained information on the year of description, distribution, size class, and taxonomic order of each known mammalian species. Our goal was to predict the size class, order, and number of mammalian species on each of four land masses—America, Eurasia, Africa, Oceania. We constructed cumulative functions of species described versus year of description, and we fitted a logarithmic model to calculate instantaneous rates of species description in 1992 and 2032 and to estimate the number of species to be described in each group in the 40‐year interval. Africa and Eurasia had the highest absolute number of species today and the greatest number of species expected to be described in species‐rich orders (except for Rodentia, in which the highest number of known and expected species was in the American land mass). Per unit area, Oceania had the highest number of known species and the greatest number of species expected to be described. Our estimates, based on the historical patterns of species accumulation, place the total number of mammalian species in the year 2032 at 4875, which is 247 more than in 1992. The majority of the new species will be small (<100 g) and will be in the orders Insectivora, Chiroptera, and Rodentia. Our analyses will help identify particular groups and land masses for which field surveys, conservation efforts, and taxonomic study deserve particular attention.