Dissimilarity measurements and the size structure of ecological communities

Abstract

Summary1. Measurements of community resemblance in ecology are often based on species composition, and the starting point for calculations is usually a site-by-species data table. However, resemblance measurements may not be sufficiently accurate when communities are described using species composition only. Characteristics such as the size of their constituting organisms are also important to understand community organization. 2. Here, we provide a framework that generalizes conventional resemblance measurements by incorporating the size structure of the compared communities. We first introduce the concept of cumulative abundance profile, which generalizes traditional species abundance values, and describe how to calculate it. We then explain our approach to compare cumulative abundance profiles in community resemblance measurements and use a small simulation study to determine which resemblance coefficients appropriately deal with compositional and structural differences. After that, we present an illustrative example where we study the structural and compositional variation between and within six Douglas-fir forest plots in British Columbia, Canada. 3. According to our investigations, the generalizations we suggest for the percentage difference (alias Bray-Curtis dissimilarity) and the Ru zi cka coefficients are appropriate to measure community resemblance in terms of size structure, species composition or both. 4. Our framework allows community resemblance to be measured in terms of either size structure or species composition, or both. A broad range of applications is expected. In the case of terrestrial plant communities, potential applications include analyses of community dynamics and classification of vegetation.

Palaeoenvironmental drivers of vertebrate community composition in the Belly River Group (Campanian) of Alberta, Canada, with implications for dinosaur biogeography

“…Rarefied data were further Wisconsin double standardized after conversion to relative abundances, again through use of the functions contained in the ‘vegan’ package [65]. The standardized relative abundance dataset was converted to the percentage-difference dissimilarity index (also referred to as Bray-Curtis) [66]. R- vs. Q-mode cluster analyses were generated for the resultant dissimilarity dataset, with UPGMA linkage, using the ‘tabasco’ function of the ‘vegan’ R package [65].…”

When rare species are not important: linking plot-based vegetation classifications and landscape-scale mapping in Australian savanna vegetation

“…Variety of life-forms and species heights are important functional characteristics of an ecosystem (Sattler and Williams 1999, Lindenmayer and Franklin 2002, De Cáceres et al 2013) as well as being key components in differentiating landscape scale plant communities (Küchler and Zonneveld 1988). For identifying landscape-scale communities, we found using actual height of the vegetation layer was necessary as it grouped sites by canopy and sub-canopy layers and was substantially better than any of the other measures in predicting species foliage cover.…”

Cross-Shore Environmental Gradients in the Western Mediterranean Coast and Their Influence on Nearshore Phytoplankton Communities

“…Similarities within phytoplankton communities along the cross-shore transects were evaluated from a taxonomic approach (lists of species or groups and abundance) using the Bray-Curtis dissimilarity index that appropriately emphasize changes in the composition or relative abundances of the identities (Legendre and Gallagher, 2001;Clarke et al, 2006;De Cáceres et al, 2013). A taxonomic resemblance matrix was calculated based on the standardized square root transformed abundance data.…”