in species richness?". Species richness ultimately depends on whatever proximate factors are found to affect processes of speciation, extinction, immigration, and emigration. While some ecologists continue to search for the ultimate primary mechanism that causes the latitudinal richness gradient, many ecologists suggest instead this ecological pattern is likely to be generated by several contributory mechanisms (Gaston and Blackburn 2000, Willig et al. 2003, Rahbek et al. 2007). For now, the debate over the cause of the latitudinal diversity gradient will continue until a groundbreaking study provides conclusive evidence, or there is general consensus that multiple factors contribute to the pattern. See also Asynchrony of Seasons Hypothesis Biodiversity Biomass (ecology) Biomes Effective evolutionary time Evolution Extinction Latitude Primary production Speciation Species richness Tropics Lists of organisms by population References References Bibliography Brown, J. H., and M. V. Lomolino. 1998. Biogeography. Sinauer Associates, Sunderland. Clarke, A., and J. A. Crame. 2003. The importance of historical processes in global patterns of diversity. Pages 130-151 in T. M. Blackburn and K. J. Gaston, editors. Macroecology Concepts and Consequences. Blackwell Scientific, Oxford. Gaston, K. J., and T. M. Blackburn. 2000. Pattern and processes in macroecology. Blackwell Scientific, Oxford. Rosenzweig, M. L. 2003. How to reject the area hypothesis of latitudinal gradients. Pages 87–106 in T. M. Blackburn and K. J. Gaston, editors. Macroecology: Concepts and Consequences. Blackwell Publishing, Oxford. Biodiversity Ecology