Dating the tree of life
Dating the TOL has also been the exclusive subject of a large, recent edited book (Hedges and Kumar, 2009a), and some molecular systematics laboratories now specialize in this task. This interest in dating the TOL is not surprising because beyond the intrinsic goal of reconstructing the history of taxonomic diversification, timetrees are required in many types of comparative analyses. Dating the Tree of Life (TOL) has become a major goal of biological research, as shown by various well-funded initiatives (at least in the USA), such as the Assembling the Tree of Life program of the National Science Foundation ( pims_id=5129), which has distributed over US $ 57 000 000 since 2006. As such, the entities that we call “species’’ and that are registered into various databases are not ontologically comparable; some are clades, some are reproductive communities, some are evolutionary lineages, others are phenetic clusters, and yet others belong to two or more of these categories. Improvements in dating the TOL would thus benefit large segments of the biological community, ranging from conservation biology and ecology through functional biology and paleontology. Recently, progress has been made on several fronts: in compiling databases and supertrees incorporating paleontological data, in computing confidence intervals on the true stratigraphic range of taxa, and in using birth-and-death processes to assess the probability distribution of the time of origin of specified taxa. Combined paleontological and molecular dating has also progressed through the insertion of extinct taxa into data matrices, which allows incorporation of their phylogenetic uncertainty into the dating analysis. Was its diversification slow and gradual, or did it occur in bursts (evolutionary radiations), and if so, when were these bursts, and what caused them?
In fact, time data are so useful that Avise and Liu (2011) have suggested to systematically add this information to taxon names.
These advances in evolutionary biology, which require timetrees, have revolutionized modern science by allowing more rigorous analyses.
Dating the Tree of Life (TOL) has become a major goal of biological research. Pubmed Abstract | Pubmed Full Text | Cross Ref Full Text Patterson, T.
Beyond the intrinsic interest of reconstructing the history of taxonomic diversification, time-calibrated trees (timetrees for short, as used throughout below) are required in many types of comparative analyses, where branch lengths are used to assess the conservation importance of lineages, correlation between characters, or to assess phylogenetic niche conservatism, among other uses.
For instance, conservation studies previously used species counts (at best) or higher taxon count (of genera, families, or even orders) to assess the biodiversity of various regions (hotspots or simply areas that could be protected to preserve as much biodiversity as possible), but all these approaches are problematic to various extents.
There is no universally accepted species concept, despite repeated attempts to unify species concepts (e.g., de Queiroz, 1998).