DOI: 10.5061/dryad.sxksn033s
title: Diversity change in forest plots of Blue Mountains, Jamaica

description: 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.
description: This is an example dataset for a mathematical paper, using data
 that was originally collected from an published empirical paper (Tanner
 and Bellingham 2006).  Tanner, E. V. J., and P. J.
 Bellingham. 2006. Less diverse forest is more resistant to hurricane
 disturbance: evidence from montane rain forests in Jamaica. Journal of
 Ecology 94:1003-1010. From the text of the current
 manuscript: We illustrate how our approach can be used
 to measure the causes of diversity change in nature using data from a
 montane tropical forest during recovery from hurricane damage. Example
 analyses are provided in (appendix S3). Tanner (1977) sampled forests in
 four sites within 25–175 m of each other that differed in topography and
 soil nutrient availability on and near the main ridge of the Blue
 Mountains of Jamaica (18°05′ N, 76°39′ W; 1580–1600 m). The Mor ridge site
 (hereafter Mor) has low soil nutrient availability, with low alpha
 diversity and several habitat specialists (Tanner 1977). The three other
 sites are more fertile, include many habitat generalists, and have higher
 alpha diversity: Col forest, Wet Slope forest, and Mull Ridge forest
 (hereafter Col, Slope and Mull, respectively; Tanner and Bellingham 2006).
 At each site all tree individuals ≥3 cm in diameter at 1.3 m height (dbh)
 were identified, tagged, and measured during an initial survey in
 1974. These sites were re-censused in 1984, then hit by
 Hurricane Gilbert in 1988, considered the most powerful hurricane in the
 Caribbean in the 20th century, and then re-censused in 1994 (Tanner and
 Bellingham 2006). The hurricane caused increased tree mortality, both
 immediately and over several years as a result of stem damage (Bellingham
 et al. 1992, Tanner et al. 2014), and widespread defoliation, increasing
 the light available in the forest floor for approximately three years
 (Bellingham et al. 1996). As a result, alpha diversity increased in some
 sites, which Tanner and Bellingham (2006) hypothesized was due to the
 recruitment of light-demanding species, but they did not quantify the
 contributions of these to overall species diversity.