Phylogenetic Comparative Methods

Phylogenetic comparative methods (PCMs) are statistical techniques that use the structure of phylogenetic trees to test evolutionary hypotheses about trait evolution, diversification rates, and adaptive radiation. They correct for the non-independence of species data — the fact that closely related species share traits due to common ancestry rather than independent adaptation — by modeling evolutionary change as a process running along the branches of a tree. PCMs include methods for estimating ancestral states, testing for correlated evolution, detecting shifts in diversification rates, and reconstructing historical biogeography.

PCMs are not merely statistical tools. They are the empirical bridge between microevolutionary processes and macroevolutionary patterns, connecting population genetics to the large-scale structure of biodiversity. The field was transformed by Joseph Felsenstein's 1985 introduction of phylogenetically independent contrasts, a technique that remains central to how evolutionary biologists analyze comparative data.