Losing history: how extinctions prune features from the tree of life

Abstract

Biodiversity provides many valuable services to humanity; however, rapid expansion of the human population has placed increasing pressure on natural systems, and it has been suggested that we may be entering a sixth mass extinction. There is an urgent need, therefore, to prioritize conservation efforts if we are to maintain the provisioning of such service in the future. Phylogenetic diversity (PD), the summed branch lengths that connect species on the treeof-life, might provide a valuable metric for conservation prioritization because it has been argued to capture feature diversity. Frequently, PD is estimated in millions of years, and therefore implicitly assumes an evolutionary model in which features diverge gradually over time. Here, I explore the expected loss of feature diversity when this assumption is violated. If evolution tends to slow down over time, as might be the case following adaptive radiations, losses of feature diversity might be relatively small. However, if evolution occurs in rapid bursts, following a punctuated model, impacts of extinctions might be much greater. PD captures many important properties, but if we use it as a proxy for feature diversity, we first need to ensure that we have the correct evolutionary model.

Multi‐dimensional biodiversity hotspots and the future of taxonomic, ecological and phylogenetic diversity: A case study of North American rodents

“…It is clear that phylogenetic and ecological diversity promote ecosystem stability and resilience in myriad ways (Cadotte et al, 2012;Davies, Urban, Rayfield, Cadotte, & Peres-Neto, 2016). Furthermore, preserving regions with deep and shallow phylogenetic diversity and diverse evolutionary modes (e.g., Davies, 2015) protects both past evolutionary heritage and future potential centres of species generation. Furthermore, preserving regions with deep and shallow phylogenetic diversity and diverse evolutionary modes (e.g., Davies, 2015) protects both past evolutionary heritage and future potential centres of species generation.…”

Reconsidering the Loss of Evolutionary History: How Does Non-random Extinction Prune the Tree-of-Life?

“…Although there are a large number of alternative models of If tip taxa A and C become extinct, we lose two branches and 3 Myrs of evolutionary history from the tree. If sister taxa A and B become extinct, for example, because they share a phylogenetically conserved trait that predisposes them to high risk, we also lose 3 Myrs of evolutionary history, but this time three branches are lost from the phylogeny evolutionary change, including the Ornstein-Uhlenbeck model which approximates stochastic evolution with stabilizing selection (Hansen 1997 ) and the early burst model that might characterize adaptive radiations (Harmon et al 2010 ), we here (see Davies and Yessoufou 2013 ;Davies 2015 ) compare the potential loss of phylogenetic diversity under two models with very different assumptions: (1) a model of phylogenetic gradualism as represented by Brownian Motion (Fig. 3a ), and (2) a punctuated model of evolution in which trait differences accumulate in bursts at speciation (Fig.…”

Biodiversity Conservation and Phylogenetic Systematics

“…However, the relationship between phylogenetic diversity, which is measured in millions of years, and feature diversity is not straightforward, but assumes a linear divergence between species over time, for example, as might be modeled under a Brownian motion process , in which trait variance increases in proportion with time, but for which evidence is mixed. (Hansen 1997 ) and the early burst model that might characterize adaptive radiations (Harmon et al 2010 ), we here (see Davies and Yessoufou 2013 ;Davies 2015 ) compare the potential loss of phylogenetic diversity under two models with very different assumptions: (1) a model of phylogenetic gradualism as represented by Brownian Motion (Fig. 3a ), and (2) a punctuated model of evolution in which trait differences accumulate in bursts at speciation (Fig.…”