Patterns of molecular evolution associated with repeatedly evolved traits

Genetic sequence data were collected from the database GenBank or other sources. Study 1: sequences represented either marine, inland saline, and freshwater eukaryote lineages. Study 2: sequences represented freshwater and terrestrial-inhabiting insect lineages. Rates of molecular evolution were compared between habitat categories using a phylogenetic framework obtained from published studies of the taxa. Study 3: sequences (available on GenBank) for hexapod lineages were tested for positive and relaxed selection in association with the origin and loss of flight ability.