Non‐neutral patterns of species abundance in grassland communities

Abstract

Although the distribution of plant species abundance in a Minnesota grassland was consistent with neutral theory, niche but not neutral mechanisms were supported by the ability of species traits to predict species abundances in three experimental grassland communities. In particular, data from 27 species grown in monoculture showed that species differed in a trait, R*, which is the level to which each species reduced the concentration of soil nitrate, the limiting soil nutrient and which is predicted to be inversely associated with competitive ability for nitrogen (N). In these N-limited habitats, species abundance ranks correlated with their predicted competitive ranks: low R* species, on average dominated. These correlations were significantly different than expected for neutral theory, which assumes the exchangeability of species traits. Additionally, we found that changes in relative abundance after environmental change (N-addition or disturbance) were not neutral but also were significantly associated with R*.

Competition–defense tradeoffs and the maintenance of plant diversity

“…If the resource and consumer manipulations used in our metaanalysis studies are viewed as discrete points along the continuous gradients used in such models, then increasing resource availability would benefit poor competitors, and reducing consumer pressure would benefit species vulnerable to predation. Indeed, there is strong empirical support that species' responses to the experimental manipulations conform to our expectations about resource and consumer limitation (17)(18)(19). For example, competitive ability of 27 grassland species was negatively correlated with their increase in abundance along a fertilization gradient (18).…”

“…Indeed, there is strong empirical support that species' responses to the experimental manipulations conform to our expectations about resource and consumer limitation (17)(18)(19). For example, competitive ability of 27 grassland species was negatively correlated with their increase in abundance along a fertilization gradient (18).…”

A stochastic biodiversity model with overlapping niche structure

“…We show that neutral patterns in niche-structured communities are more likely when niches are, on average, sufficiently broad and overlapping. One corollary of this is that in tropical forests, coral reefs, and other systems (Volkov et al 2007;Muneepeerakul et al 2008;Latimer et al 2005;Harpole and Tilman 2006) for which neutral predictions are upheld, our model suggests that the majority of species may be broad-niche generalists. The converse of this is that non-neutral patterns of biodiversity (e.g., Fuller et al 2005) could imply a preponderance of narrow-niche specialists (i.e., a small h max ), or else a trade-off mechanism that allows narrow-niche specialists to maintain demographic equivalence with broad-niche generalists.…”

Neutral Theory Overestimates Extinction Times in Nonhuman Primates

“…Although species are not ecologically neutral, some empirical data support the predictions of neutral theory (Hubbell 2001). However, other studies have shown little agreement between empirical data and neutral simulations (Fargione et al 2003;Jabot and Chave 2009;Karst et al 2005;Ricklefs and Renner 2012;Stanley Harpole and Tilman 2006). The majority of studies focus on the ecological implications that arise when field data of current distribution and species abundance differ from predicted ones (Siepielski et al 2010;Volkov et al 2005).…”