The analyses presented in Sects. 8.4.3.4 and 8.4.3.5 have all been conducted with
the Jaccard-based Podani replacement and richness difference indices. We suggest
readers to repeat the exercise with the corresponding quantitative Ružička-based
indices, with the Sørensen-percentage difference indices, and also with the Baselga
family of indices.
8.5 Functional Diversity, Functional Composition
and Phylogenetic Diversity of Communities
Although we focus in this chapter on taxonomic (species) diversity, we cannot end it
without briefly introducing what has become a popular research field in community
ecology and functional ecology. Functional diversity is, with taxonomic and phylogenetic diversities, one of the three facets of biodiversity at the community level.
Here, we shall restrict ourselves to the principles and applications of two recent
approaches that are widely used nowadays in functional community ecology. The
first approach is a flexible distance-based framework to compute alpha functional
diversity indices from multiple traits (Villéger et al. 2008, Laliberté and Legendre
2010). The second one is part of the unified framework that we mentioned in Sect.
8.4.1 about the partitioning of diversity into alpha, beta and gamma components
(de Bello et al. 2010), and is based on Rao’s quadratic entropy (Botta-Dukát 2005).
8.5.1 Alpha Functional Diversity
Using a distance-based approach, Villéger et al. (2008) proposed to distinguish three
independent components in the functional diversity of a given community: functional richness (FRic) represents the amount of functional space filled by a community, i.e. the volume of the minimum convex hull that includes all species present in
the multidimensional space of functional traits; functional evenness (FEve) measures
the regularity of the abundance distribution of the species along the minimum
spanning tree that links the species points in multidimensional functional space;
functional divergence (FDiv) relates to how species abundances are distributed
within the functional trait space. FEve and FDiv are constrained between 0 and
1. The functional trait space may be either the raw species trait matrix if all traits are
quantitative and continuous, or the space obtained from a PCoA of the Gower
dissimilarity matrix computed on the mixed trait matrix.
Another distance-based multi-trait diversity index, called functional dispersion
(FDis), has been added to the framework by Laliberté and Legendre (2010). It is the
mean distance of individual species to the centroid of all species in the
404
8 Community Diversity
the Jaccard-based Podani replacement and richness difference indices. We suggest
readers to repeat the exercise with the corresponding quantitative Ružička-based
indices, with the Sørensen-percentage difference indices, and also with the Baselga
family of indices.
8.5 Functional Diversity, Functional Composition
and Phylogenetic Diversity of Communities
Although we focus in this chapter on taxonomic (species) diversity, we cannot end it
without briefly introducing what has become a popular research field in community
ecology and functional ecology. Functional diversity is, with taxonomic and phylogenetic diversities, one of the three facets of biodiversity at the community level.
Here, we shall restrict ourselves to the principles and applications of two recent
approaches that are widely used nowadays in functional community ecology. The
first approach is a flexible distance-based framework to compute alpha functional
diversity indices from multiple traits (Villéger et al. 2008, Laliberté and Legendre
2010). The second one is part of the unified framework that we mentioned in Sect.
8.4.1 about the partitioning of diversity into alpha, beta and gamma components
(de Bello et al. 2010), and is based on Rao’s quadratic entropy (Botta-Dukát 2005).
8.5.1 Alpha Functional Diversity
Using a distance-based approach, Villéger et al. (2008) proposed to distinguish three
independent components in the functional diversity of a given community: functional richness (FRic) represents the amount of functional space filled by a community, i.e. the volume of the minimum convex hull that includes all species present in
the multidimensional space of functional traits; functional evenness (FEve) measures
the regularity of the abundance distribution of the species along the minimum
spanning tree that links the species points in multidimensional functional space;
functional divergence (FDiv) relates to how species abundances are distributed
within the functional trait space. FEve and FDiv are constrained between 0 and
1. The functional trait space may be either the raw species trait matrix if all traits are
quantitative and continuous, or the space obtained from a PCoA of the Gower
dissimilarity matrix computed on the mixed trait matrix.
Another distance-based multi-trait diversity index, called functional dispersion
(FDis), has been added to the framework by Laliberté and Legendre (2010). It is the
mean distance of individual species to the centroid of all species in the
404
8 Community Diversity