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how the approach might be extended to consider future trends in anthropogenic drivers, to identify likely future battlegrounds of mammalian conservation, and the likely casualties. This framework could help to highlight consequences of choosing among different future climatic and socioeconomic scenarios. We end by discussing priority-setting, showing how alternative currencies for diversity can suggest very different priorities. We argue that aiming to maximize long-term evolutionary responses is inappropriate, that conservation planning needs to consider costs as well as benefits, and that proactive conservation of largely intact systems should be part of a balanced strategy.

The Tree of Life—phylogeny—is a powerful metaphor for life’s diversity, showing all species, including our own, as part of an interrelated whole. But phylogeny is more than a metaphor. It is also a research tool—the result of evolutionary processes integrated over the history of life, it can be analyzed for insights into how those processes have shaped today’s biota (Harvey et al., 1996). This approach is becoming increasingly powerful as the trees become ever more inclusive, built from rapidly accumulating databases using methods that continue to be improved (Bininda-Emonds, 2004; Cracraft and Donoghue, 2004).

Species’ histories are of interest, but their futures are of more pressing concern. The Tree of Life is currently under sustained attack, as people increasingly dominate landscapes (Millennium Ecosystem Assessment, 2005a). Comparisons of extinction rates between today and geological history are difficult for many reasons (Jablonski, 1994), but the Tree of Life is already being pruned more quickly than it is growing (Purvis and Hector, 2000), and extinction rates are projected to rise by at least another order of magnitude over the next centuries (Mace et al., 2005). This chapter describes how phylogeny has a role to play in understanding the pattern of survivors and casualties and how it can help us both to predict species’ futures and to estimate some of the biodiversity value that would be lost if they went extinct.

We focus on mammals as a model system. They are much better known than almost any other group, with a mature species-level taxonomy (Wilson and Reeder, 2005), a largely complete evaluation of species’ extinction risk (Baillie et al., 2004), a large database of ecological, life history, and geographical information (K.E.J., J.B., A.P., C.D.L.O., S.A.F., Christina Connolly, Amber Teacher, J.L.G., R.G., Elizabeth Boakes, Michael Habib, Janna Rist, Chris Carbone, Christopher A. Plaster, O.R.P.B.-E., Janine K. Foster, Elisabeth A. Rigby, Michael J. Cutts, Samantha A. Price, Wes Sechrest, Justin O’Dell, Kamran Safi, M.C., and G.M.M., unpublished data), and a comprehensive species-level estimate of phylogeny

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