Reconciling the concepts and measures of diversity, rarity and originality in ecology and evolution

Abstract

The concept of biological diversity, or biodiversity, is at the core of evolutionary and ecological studies. Many indices of biodiversity have been developed in the last four decades, with species being one of the central units of these indices. However, evolutionary and ecological studies need a precise description of species' characteristics to best quantify inter‐species diversity, as species are not equivalent and exchangeable. One of the first concepts characterizing species in biodiversity studies was abundance‐based rarity. Abundance‐based rarity was then complemented by trait‐ and phylo‐based rarity, called species' trait‐based and phylogenetic originalities, respectively. Originality, which is a property of an individual species, represents a species' contribution to the overall diversity of a reference set of species. Originality can also be defined as the rarity of a species' characteristics such as the state of a functional trait, which is often assumed to be represented by the position of the species on a phylogenetic tree. We review and compare various approaches for measuring originality, rarity and diversity and demonstrate that (i) even if attempts to bridge these concepts do exist, only a few ecological and evolutionary studies have tried to combine them all in the past two decades; (ii) phylo‐ and trait‐based diversity indices can be written as a function of species rarity and originality measures in several ways; and (iii) there is a need for the joint use of these three types of indices to understand community assembly processes and species' roles in ecosystem functioning in order to protect biodiversity efficiently.

Functionally unique, specialised, and endangered (FUSE) species: towards integrated metrics for the conservation prioritisation toolbox

“…Species' FSp was computed as the Euclidean distance of each species to the barycentre of the multidimensional trait space (Mouillot et al 2013). We did not investigate the functional distinctiveness (Fdist) in Pimiento et al (2020), but we include here as this metric is commonly used in other studies and is a general descriptor of a species' mean dissimilarity to all others in the community (Grenie et al 2018;Kondratyeva et al 2019;Violle et al 2017). Note that computing FUn and Fdist does not require the Euclidean trait space; rather, they can be directly calculated based on the Gower's distance matrix (Kondratyeva et al 2019).…”

“…Building on this framework, species' extinction risk has been combined with evolutionary distinctiveness to identify 'evolutionarily distinct and globally endangered' (EDGE) species (Isaac et al 2007). There have also been recent efforts to integrate information on species' functional distinctiveness and rarity, as indicated by range size (Grenie et al 2018;Kondratyeva et al 2019;Violle et al 2017), and to incorporate functional diversity into spatial conservation planning (Pollock et al 2017). However, there have been limited efforts to combine functional contributions to the more encompassing assessments of risk provided by the IUCN (but see Hidasi-Neto et al 2015).…”

adiv: An r package to analyse biodiversity in ecology

“…Hill, 1973) and recent approaches that measure trait‐based and phylogenetic diversity (e.g. Chao, Chiu, & Jost, 2010; Faith, 1992; Kondratyeva, Grandcolas, & Pavoine, 2019; Pavoine, Baguette, & Bonsall, 2010; Pavoine, Love, & Bonsall, 2009; Pavoine & Ricotta, 2019). In addition, all approaches can be easily applied to other aspects of diversity.…”

On islands, evolutionary but not functional originality is rare

“…Originality can refer to evolutionary history or to functional traits (e.g. Kondratyeva, Grandcolas & Pavoine, 2019;Pavoine, Ollier, & Dufour, 2005;Pavoine et al, 2017;Redding, Mazel, & Mooers, 2014 ;Mouillot, Culioli, Pelletier, & Tomasini, 2008 ;Violle et al, 2017). Originality has been poorly investigated in community ecology or biogeography (but see Mouillot, Graham, Villéger, Mason, & Bellwood, 2013) but its value for biodiversity conservation is well supported.…”

“…Originality has been poorly investigated in community ecology or biogeography (but see Mouillot, Graham, Villéger, Mason, & Bellwood, 2013) but its value for biodiversity conservation is well supported. Indeed, in addition to capture significant amount of phylogenetic or functional diversity Faith, 1992;Kondratyeva et al 2019), evolutionary and functionally original species may insure key ecosystem processes and provide services to humanity. Functional and evolutionary originality may sometimes be decoupled (Faith, 1992;Pollock, Thuiller, & Jetz, 2017) and should be differentiated due to the distinct benefits they may provide.…”