  A wide variety of stochastic models of cladogenesis (based on speciation and
extinction) lead to an identical distribution on phylogenetic tree shapes once
the edge lengths are ignored. By contrast, the distribution of the tree's edge
lengths is generally quite sensitive to the underlying model. In this paper, we
review the impact of different model choices on tree shape and edge length
distribution, and its impact for studying the properties of phylogenetic
diversity (PD) as a measure of biodiversity, and the loss of PD as species
become extinct at the present. We also compare PD with a stochastic model of
feature diversity, and investigate some mathematical links and inequalities
between these two measures plus their predictions concerning the loss of
biodiversity under extinction at the present.
