PHYLOGENETIC ANALYSIS OF WING FEATHER TAXIS IN BIRDS: MACROEVOLUTIONARY PATTERNS OF GENETIC DRIFT?

Abstract Most recent research on character evolution attempts to identify either (1) homology or homoplasy (systematic use of the term character), or (2) the adaptive function or selective regime underlying the origin of a character (“adaptationist” use of the term character). There have been relatively few serious considerations or examples of neutral character evolution above the molecular level. Wing feather taxis in birds, the presence or absence of the fifth secondary feather, provides an intriguing possible example of nonadaptive character evolution. We examine the phylogenetic pattern of wing feather taxis among birds to (1) determine its polarity in modern birds (Neornithes), (2) hypothesize the frequency and taxonomic locations of changes in the taxic state, (3) test whether taxis is relatively labile or inert phylogenetically, and (4) allow preliminary consideration of whether adaptive or selectively neutral processes have produced those patterns. Minimum tree length necessary to explain the dis...