TREES WITHIN TREES - PHYLOGENY AND HISTORICAL ASSOCIATIONS

The association between two or more lineages over evolutionary time is a recurrent theme spanning several different fields within biology, f rom molecular evolution to coevolution and biogeography. In each 'hist orical association', one lineage is associated with another, and can b e thought of as tracking the other over evolutionary time with a great er or lesser degree of fidelity. Examples include genes tracking organ isms, parasites tracking hosts and organisms tracking geological and g eographical changes. Parallels among these problems raise the tantaliz ing prospect that each is a special case of a more general problem, an d that a single analytical tool can be applied to all three kinds of a ssociation.