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Biogeographic Affinity Helps Explain Productivity‐Richness Relationships at Regional and Local Scales
Susan Harrison and James B. Grace
The American Naturalist
Vol. 170, No. S2, Merging Evolutionary and Ecological Approaches to Understanding Geographic Gradients in Species RichnessA Symposium Organized by Susan Harrison (August 2007), pp. S5-S15
Stable URL: http://www.jstor.org/stable/10.1086/519010
Page Count: 11
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Abstract: The unresolved question of what causes the observed positive relationship between large‐scale productivity and species richness has long interested ecologists and evolutionists. Here we examine a potential explanation that we call the biogeographic affinity hypothesis, which proposes that the productivity‐richness relationship is a function of species’ climatic tolerances that in turn are shaped by the earth’s climatic history combined with evolutionary niche conservatism. Using botanical data from regions and sites across California, we find support for a key prediction of this hypothesis, namely, that the productivity–species richness relationship differs strongly and predictably among groups of higher taxa on the basis of their biogeographic affinities (i.e., between families or genera primarily associated with north‐temperate, semiarid, or desert zones). We also show that a consideration of biogeographic affinity can yield new insights on how productivity‐richness patterns at large geographic scales filter down to affect patterns of species richness and composition within local communities.
© 2007 by The University of Chicago.