Diversity change in forest plots of Blue Mountains, Jamaica

Beta diversity describes the differences in species composition among
communities. Changes in beta diversity over time are thought to be due to
selection based on species’ niche characteristics. For example, theory
predicts that selection that favours habitat specialists will increase
beta diversity. In practice, ecologists struggle to predict how beta
diversity changes. To remedy this problem, we propose a novel solution
that formally measures selection’s effects on beta diversity. Using the
Price equation, we show how change in beta diversity over time can be
partitioned into fundamental mechanisms including selection among species,
variable selection among communities, drift, and immigration. A key
finding of our approach is that a species’ short-term impact on beta
diversity cannot be predicted using information on its long-term
environmental requirements (i.e. its niche). We illustrate how our
approach can be used to partition causes of diversity change in a montane
tropical forest before and after an intense hurricane. Previous work in
this system highlighted the resistance of habitat specialists and the
recruitment of light-demanding species but was unable to quantify the
importance of these effects on beta diversity. Using our approach, we show
that changes in beta diversity were consistent with ecological drift. We
use these results to highlight the opportunities presented by a synthesis
of beta diversity and formal models of selection.