Patterns in the diversity of the world’s land vertebrate genera Michael L. Rosenzweig 1,2 , Vanessa Buzzard 1 , John Donoghue II 1 , Gavin Lehr 2 , Natasha Mazumdar 3 , Haley M. Rasmussen 4 , Irena Simova 5 , Scott Trageser 1 , Heather Wernett 1 and Jingzi Xu 6 1 Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona, USA, 2 College of Science, University of Arizona, Tucson, Arizona, USA, 3 College of Fine Arts, University of Arizona, Tucson, Arizona, USA, 4 College of Education, University of Arizona, Tucson, Arizona, USA, 5 Center for Theoretical Study, Prague, Czech Republic and 6 Department of Environmental Sciences, East China Normal University, Shanghai, China ABSTRACT Background: The number of species of terrestrial vertebrate in one of the world’s great zoological regions fits a linear combination of area (A) and one climatic variable – either annual actual evapotranspiration (AE) or mean annual temperature (T) – with an R 2 of 0.97. The same is true of species diversity in the four separate classes of terrestrial vertebrate; their R 2 -values range from 0.90 to 0.95. Goals: Determine whether the number of genera, G, fits the same or a similar pattern. Measure the relationship between G and S (the number of species). Estimate the effect of total breakdown of biogeographical barriers on G. Data: The global terrestrial vertebrate data sets of the World Wildlife Fund. We used 755 of their 825 ecoregions and all 24,992 species in those 755 ecoregions. The WWF ecoregion data sets have names, locations, ID numbers, areas, and 102 climatic variables. Results: The patterns for area, temperature, AE, and genera closely follow the patterns for species. Area, by itself, significantly fit the number of genera in the zoological regions. But a linear combination of log A and log AE significantly improved that fit. It closely and sig- nificantly fit log G (R 2 = 0.972). The same was true of a linear combination of log A and T (R 2 = 0.964). Each of the separate classes of vertebrate exhibited the same patterns as total G, although their R 2 -values were slightly less. Neither climate variable was significant by itself in any case. G also fit the number of species very closely (R 2 = 0.99). The fit is a power function with a coefficient of 0.77, so that there are more species per genus in provinces with high than low diversity. The Neotropics (most diverse) have 5.22 species per genus; Hawaii (least diverse) has 1.74 species per genus. The advent of the Homogocene (complete homogenization of the world’s zoological regions) would cause the extinction of 49% of her terrestrial vertebrate genera, leaving sustainable only 2239 of the 4416 now sustainable. In addition, loss of natural terrestrial area would further reduce sustainable G. For example, loss of 80% of the area (the Correspondence: M.L. Rosenzweig, Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721-0088, USA. e-mail: scarab@u.arizona.edu Consult the copyright statement on the inside front cover for non-commercial copying policies. Evolutionary Ecology Research, 2013, 15: 869–882 © 2013 Miohael L. Rosenzweig