 Diversification rate

A diversification rate describes change in the number of evolutionary lineages. Under a simple branching model with speciation rate $\lambda$ and extinction rate $\mu$, net diversification is $r=\lambda -\mu$. Equal net rates can therefore arise from slow turnover or from rapid speciation accompanied by rapid extinction.

An observed accumulation of living lineages does not uniquely identify both component rates. Fossils can supply additional evidence about extinct branches, with taphonomy and sampling affecting which histories are observed.