PHYLOGENY AND EVOLUTIONARY ECOLOGY OF MODERN SEADUCKS (ANATIDAE, MERGINI)

Phylogenetic relationships of modem seaducks (Mergini) were investigat ed using a cladistic analysis of 137 morphological characters. The ana lysis produced a single tree (consistency index = 0.692, excluding aut apomorphies) with complete resolution of the relationships among the 2 5 taxa recognized. Phylogenetic inferences include: (1) the elders (Po lysticta and Somateria) constitute a monophyletic group and are the si ster-group of other Mergini; (2) the remaining generic groups of Mergi ni, sequenced in order of increasingly close relationship, are Histrio nicus, Melanitta + Camptorhynchus: Clangula, Bucephala + Mergellus, Lo phodytes, and Mergus; (3) Somateria is monophyletic with S. fischeri t he sister-group of its congeners; (4) the black scoters (Melanitta nig ra-group) are the sister-group of other scoters; (5) the Bufflehead (B ucephala albeola) is the sister-group of the goldeneyes (B. clangula a nd B. islandica); and (6) relationships among mergansers are as presen ted by Livezey (1989). Bootstrapping revealed that the placement of th e Smew as the sister-group of the goldeneyes is only weakly supported, and ancillary analyses revealed that this placement is only one step shorter than its reduction to a trichotomy with the goldeneyes and mer gansers (including Lophodytes). A phylogenetic classification of moder n seaducks is presented. The Harlequin Duck (H. histrionicus), Long-ta iled Duck (Clangula hyemalis), and Steller's Elder (Polysticta steller i) are highly autapomorphic. Evolutionary patterns of selected ecomorp hological characteristics-including body mass, sexual size dimorphism, dutch size, relative clutch mass, nest site, diet, diving method, for mation of creches, and biogeography-are examined with respect to the p hylogenetic hypothesis.