Diversity Defined

摘要

Large life on Earth shows striking gradients of diversity: from the poles to the tropics and from low to high altitude. Whether such large-scale gradients also apply to microorganisms, however, has been controversial. Stomp et al. took advantage of a comprehensive data set collected by the U.S. Environmental Protection Agency in 1973-1975. A range of physicochemical data and phytoplankton wa: sampled from 540 lakes, three times each year. The data were put through regression analysis to identify the most important local environmental variables affecting species richness, as well as a structural equation model to test for links between biodiversity, environmental variables, and geographical location. Although lake area and depth strongly influenced phytoplankton diversity, there was an overall signal of decreasing diversity as latitude and altitude increased, which reflected the overall topography of the United States. This work, when considered alongside other species richness analyses of microorganisms, suggests that very small organisms are subject to similar constraints governing large-scale distribution as the very large. - CA