Chapter 22 : Microbial Endemism and Biogeography

Conceptual figure showing alternative biogeography and body size models. Finlay (2002) has proposed that an ubiquity and biodiversity transition occurs at a body length of 1 to 10 mm, which suggests that many protozoa and nearly all prokaryotes are cosmopolitan (solid line). Alternatively, the apparent ubiquity and biodiversity transition may represent the size at which the morphospecies concept decays, and future molecular studies may show that most microbial species have distinct biogeographies, as do larger organisms (dotted line). It is likely that the percentage of microbes with distinct biogeographical patterns lies somewhere between the two extreme models (question mark).

Conceptual figure showing the enormous effect of biogeography and body size models on biodiversity estimates. According to Finlay's model (2002) , most of the species diversity on this planet would be in the size range of small insects (solid line). Alternatively, extrapolation of the body size and species diversity relationship ( May, 1988 ) to include microbes would yield a vastly greater number of prokaryotic species (dotted line). In reality microbial diversity may lie between the two extremes (question mark).