232 Endemism Table Vertebrate and higher plant endemism in the world’s 17 megadiversity countries Country Area (km2 Â 103) Mammals Birds Reptiles Amphibians Plants Brazil 8512.0 1916.6 Colombia 1141.7 Mexico 1972.5 Australia 7686.8 140 (3) 210 (1) 77 (8) 77 (7) 116 (5) 44 (12) 46 (11) 57 (9) 21 4191 (3) 397 (1) 4142 (5) 125 (6) 355 (2) 103 (8) 99 (9) 183 (4) 52 (12) 109 (7) 85 (10) 37 172 (5) 150 (6) 97 (11) 368 (2) 616 (1) 274 (3) 133 (7) 131 (8) 187 (4) 98 (10) 79 294 (2) 100 (11) 367 (1) 169 (6) 169 (5) 176 (3) 175 (4) 44 ca 17,500 Indonesia 131 (4)a 201 (2) 28 101 (6) 11 27 27 28 71 (11) 45 11 23 Madagascar China Philippines 587.0 9561.0 300.8 India 3287.8 Peru 1285.2 PNG Papua New Guinea 475.4 Ecuador 283.6 United States 9372.1 Venezuela Malaysia South Africa Democratic Republic of Congo 912.1 329.7 1221.0 2344.0 a 114 (9) 90 57 68 76 33 110 (10) 489 (12) 134 (8) 138 (7) 126 (9) 76 57 36 53 ca 16,000 ca 16,000 ca 12,500 14,458 ca 9200 ca 10,000 ca 5000 ca 7500 5356 ca 13,000 ca 4500 4036 ca 6000 ca 7250 16,500 3200 Figures in parentheses are rankings for the number of endemic species among the top 12 countries isolates in marginal habitats Therefore, historical processes, contemporary ecological factors, and inherent biological properties of lineages are involved In many cases, historical factors may be overriding, resulting in a poor relationship between measures of endemism and explanatory variables reflecting the contemporary environment Establishing correlates is a useful step in explaining patterns and causes of endemism Most pertinent studies have addressed the following question: When compared to more widespread taxa, are endemics, however defined, a random subset of the biota with regard to abiotic and biotic factors? Developing these profiles, however, has been complicated by different definitions of endemism, multiple interactions between different traits, and a failure to consider phylogenetic relatedness This section provides a brief review of the abiotic and biotic interspecific correlates of narrow range size, and concludes with an assessment of the role of endemism in speciation species) and geographical vicariants often have narrow range sizes However, there are also many cases where patterns of endemism and diversity are largely noncoincident Examples include plants in the Neotropics, birds in the Andes, dragonflies and terrestrial vertebrates in southern Africa, and the biotas of many oceanic islands and deserts Area As a generalization, proportionate and absolute measures of endemism increase with increasing area (see Figure 1), irrespective of the taxonomic level However, the relationship between number of endemic species (counts) and area is not as tight as that for the more widely studied species–area relationship This results from the lack of congruence between endemism and richness in many areas (e.g., arid lands and oceanic islands) Abiotic Environmental Factors Regional Species Richness There is often a positive relationship between the incidence of endemism and regional-scale richness This results from the importance of high habitat-related and geographical compositional turnover (beta and gamma diversity, respectively) in producing regional richness Habitat specialists (or stenotopic Levels of endemism may vary in a predictable way along gradients of rainfall, temperature, productivity, and habitat heterogeneity Models that accurately predict levels of endemism on the basis of easily measurable environmental variables have been used for the rapid identification of endemic-rich areas