Recent Progress in Assessing Palaeobiodiversity and Its Evolution

Abstract

Palaeobiodiversity used to be quantified by taxon counts at a given rank (especially families, and orders). The limitations of this approach linked with the subjective rank assignment of taxa has prompted the development of new, more objective and sophisticated methods. Thus, phylogenetic diversity (the sum of branch lengths, which represent evolutionary time) can quantify biodiversity at a given time. This requires knowing, with reasonably good precision, the appearance dates of taxa. The main problem is that the fossil record directly provides only minimal divergence dates that may be much younger than actual divergence dates. In the last few years, several methods have been used to estimate actual divergence dates. Of these, those using birth and death models or total evidence dating appear especially promising, although they are still in their infancy. Biodiversity evolution is even more difficult to tackle because of taphonomic biases and because species turnover may seem rapid in geological time. Birth and death models can be used to quantify diversification and extinction rates using timetrees. Until recently, these models made very little use, if any, of fossil data, but recent developments allow extinct taxa represented by fossils and incorporated directly into time trees to inform the analyses and reduce estimation errors.