Biogeographic Affinity Helps Explain Productivity-Richness Relationships at Regional and Local Scales

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.

Range size, taxon age and hotspots of neoendemism in the California flora

“…These earlier analyses found that increased diversity was associated with increased precipitation, topographic heterogeneity and decreased temperature seasonality. Harrison & Grace (2007) have also shown relationships between species richness and productivity based on plant diversity of serpentine-containing regions of the state. At this point, we do not know whether the differences between our study and these previous analyses are attributed to the scale of analysis, the distributional datasets or the analysis of the entire flora versus our focus on the state endemics.…”

Forest productivity and tree diversity relationships depend on ecological context within mid-Atlantic and Appalachian forests (USA)

“…The mechanisms influencing broad-scale patterns of species diversity (Rosenzweig, 1995;Wang et al, 2009;Clark, 2010), productivity of ecosystems (Huston and Wolverton, 2009), and the relationship between diversity and productivity form the basis of much ecological theory (Grime, 1973;Huston, 1994;Waide et al, 1999;Mittelbach et al, 2001;Harrison and Grace, 2007;Hillebrand and Cardinal, 2010). Understanding the factors that influence relationships between ecosystem productivity and species diversity may provide important insights into the management of ecosystems for carbon retention and the protection of hotspots of biological diversity (Huston, 1994;Mittelbach et al, 2001).…”

Determinants of Northerly Range Limits along the Himalayan Bird Diversity Gradient

“…In these latter hypotheses, emphasis has been placed on how climatic tolerances set range limits (Wiens and Graham 2005;Wiens et al 2010). Aspects of climate that might limit ranges include temperature (Root 1988), freezing per se (Wiens and Donoghue 2004), precipitation (Harrison and Grace 2007), and variability in temperature (Wiens et al 2006). Ecological competition may also contribute to range limits in these nonequilibrium models (Wiens et al 2010; i.e., species well adapted to a particular climatic regime indefinitely outcompete species adapted to a different regime, but numbers can increase through within-regime diversification).…”

“…For example, because of an inability to deal with freezing, entire tropical clades may be restricted to the tropics (Wiens et al 2006), or because of the inability to deal with water stress, few clades contain species that make the transition to deserts (Harrison and Grace 2007). These hypotheses therefore depend on so-called niche conservatism, which we define, following Wiens et al (2010), as the retention of ecological traits over time.…”