Extinction and the loss of functional diversity

Abstract

Although it is widely thought to in uence ecosystem processes, there is little consensus on an appropriate measure of functional diversity. The two major perspectives, to date, are to assume that every species is functionally unique, or to assume that some species are functionally identical, such that functional groups exist. Using a continuous measure of functional diversity (FD) derived from the quantitative functional traits of species, we show that the loss of functional diversity from six natural assemblages was rapid compared with rates of loss from comparable simulated assemblages. Loss of FD occurred faster than loss of functional-group diversity in four of the six natural assemblages. Patterns of functional-group diversity loss depended on the number of functional groups and the number of species in an assemblage. Extinctions that occurred rst for species with particular traits (e.g. low leaf nitrogen concentration, deep roots and large body size) caused greater loss of FD than expected by chance in four of the six natural assemblages. In two real assemblages, these trait-dependent extinctions had more severe effects on FD than our simulated worst-case extinction scenario. These data suggest that conserving a large proportion of the functional traits of species requires conserving a large proportion of all species.

Global priorities for conservation across multiple dimensions of mammalian diversity

“…Table 2. Percentage of global total of species richness, phylogenetic diversity (14), trait diversity (20), and number of threatened species that are retained within the top 17% of the important regions for each dimension (taxonomic, phylogenetic, and functional) and across all three dimensions (overlap priorities) from the zonation prioritization analyses and in currently protected areas % of the global total all these aspects of biodiversity. The small fraction of areas (4.6%) where there was overlap across the dimensions should receive special conservation attention.…”

“…First, we calculated the Kendall rank correlation to evaluate how the conservation priority values of the cells for the prioritization based on each dimension (taxonomic/phylogenetic/trait) related to each other and to species richness and to the number of threatened species. Then, to evaluate how much the spatial priorities of each dimension captured the existing taxonomic, functional, and phylogenetic diversity of terrestrial mammals, we calculated the global amount of species richness, the number of threatened mammals, phylogenetic diversity (the PD index) (14), and functional diversity (the FD index) (20). Last, we assessed how much of the global total of each index was captured proportionally by the conservation solution for each dimension and by the overlapping areas among all dimensions.…”

“…However, the relationships among these dimensions across the globe are poorly understood and vary depending on the metric used and the scale of the analysis (15,23). Some studies have shown a high correlation among taxonomic, phylogenetic, and trait diversity of global mammals (23,24), especially when using diversity indices affected by species richness, i.e., phylogenetic diversity (14) and functional diversity (20). For example, species richness was an effective surrogate for the functional and phylogenetic dimensions of local rodent assemblages in Manu (25).…”

“…Evolutionary history captures the uniqueness of linages through deep time (16) and can influence species' susceptibility to extinction, because extinction risk is phylogenetically nonrandom (17)(18)(19). The trait dimension reflects ecological, morphological, and physiological strategies of species (20). Therefore losses in all three dimensions could have large consequences for biodiversity and ecosystem function (13).…”

Understanding global patterns of mammalian functional and phylogenetic diversity

“…The inadequacy of species richness in representing the differences in evolutionary history, how communities function, and how the network of interactions within communities are organized has led to the development of alternative measures, mainly phylogenetic diversity (PD) and functional diversity (FD) [4][5][6][7]. The rationale behind the use of these alternative diversity measures is to better identify the underlying processes determining species richness and ecosystem functioning [8,9].…”