![]() That reaches an asymptote when all species (and branch segments) are represented (Fig. Thus, just like species richness, PD increases monotonically with increasing sampling effort That is, the addition of individuals or sets of individuals to a communityĬan increase PD but never decrease it. , has the property of concavity (Lande 1996). 2010, and chapter “ Phylogenetic Diversity Measures and Their Decomposition: A Framework Based on Hill Numbers”) have been developed, for example. 2009), ecological resemblance (Ferrier et al. By this means, phylogenetically weighted measures of endemism (Faith et al. By substituting branch segments (intervals between nodes on a phylogenetic tree) for species, and including a weighting for the length of that segment, it is possible to modify many of the classic measures of Species Diversity The common feature of this class of measures is the summation of branch length , but rather a general class of measures dealing with various aspects of alpha and beta-diversity Has come to be not just a single measure equating to a phylogenetically weighted form of richness Since the original formulation by Faith ( 1992), PD Further, the tree itself might not portray evolutionary relationships but instead be, for example, a cluster dendrogram portraying functional relationships among taxa (Petchey and Gaston 2002). , Operational Taxonomic Units, Evolutionarily Significant Units, individual organisms or unique haplotypes. Thus, the tips do not, by necessity, need to represent species but could be higher taxa PD is a particularly flexible measure because it can be applied to any set of relationships among entities that can be reasonably portrayed as a tree. The PD of a set of taxa, represented as the tips of a phylogenetic tree, is the sum of the branch length ) is a simple, intuitive and effective measure of biodiversity Future prospects for PD rarefaction include the recognition of evolutionary hotspots (independent of species richness), the basis for ecological theory such as phylogeny-area relationships, and the prediction of unseen biodiversity. The application of rarefaction of PD to sample standardisation and measurement of phylogenetic evenness, phylogenetic beta-diversity and phylogenetic dispersion is demonstrated. This extension, termed ∆PD, is simply the initial slope of the rarefaction curve and is related to entropy measures such as PIE (Probability of Interspecific Encounter) and Gini-Simpson entropy. However, the solution can be simply extended to create measures of phylogenetic evenness, phylogenetic beta-diversity and phylogenetic dispersion, derived from individual-based, sample-based and species-based curves respectively. Rarefaction is commonly applied as a standardisation for diversity values derived from differing numbers of sampling units. The formulation for the exact analytical solution for the rarefaction of PD is given in an expanded form to demonstrate congruence with the classic formulation for the rarefaction of species richness. sites), or even species (or equivalent), giving individual-based, sample-based and species-based curves respectively. Accumulation units represent individual organisms, collections of organisms (e.g. This relationship can be described by a rarefaction curve tracing the expected PD for a given number of accumulation units. Like other measures of diversity, Phylogenetic Diversity (PD) increases monotonically and asymptotically with increasing sample size.
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