Partitioning the turnover and nestedness components of beta diversity

TLDR

Beta diversity reflects variation in species composition across assemblages and can be decomposed into spatial species turnover and nestedness, arising from species replacement and loss, respectively. This paper provides a unified framework and proposes two families of beta‑diversity measures to assess and separate spatial turnover and nestedness in both pairwise and multiple‑site contexts. Each family includes a comprehensive beta‑diversity metric that is additively decomposed into pure turnover and nestedness components, and the approach is illustrated with a case study of European longhorn beetles. The additive partitioning demonstrates that distinguishing turnover from nestedness is essential for interpreting the causal processes of biodiversity and for addressing key biogeographic, ecological, and conservation questions.

Abstract

ABSTRACT Aim Beta diversity (variation of the species composition of assemblages) may reflect two different phenomena, spatial species turnover and nestedness of assemblages, which result from two antithetic processes, namely species replacement and species loss, respectively. The aim of this paper is to provide a unified framework for the assessment of beta diversity, disentangling the contribution of spatial turnover and nestedness to beta‐diversity patterns. Innovation I derive an additive partitioning of beta diversity that provides the two separate components of spatial turnover and nestedness underlying the total amount of beta diversity. I propose two families of measures of beta diversity for pairwise and multiple‐site situations. Each family comprises one measure accounting for all aspects of beta diversity, which is additively decomposed into two measures accounting for the pure spatial turnover and nestedness components, respectively. Finally, I provide a case study using European longhorn beetles to exemplify the relevance of disentangling spatial turnover and nestedness patterns. Main conclusion Assigning the different beta‐diversity patterns to their respective biological phenomena is essential for analysing the causality of the processes underlying biodiversity. Thus, the differentiation of the spatial turnover and nestedness components of beta diversity is crucial for our understanding of central biogeographic, ecological and conservation issues.