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PHYLOGENY AND COMPARATIVE ECOLOGY OF STIFF-TAILED DUCKS (ANATIDAE: OXYURINI)

1995; Wilson Ornithological Society; Volume: 107; Issue: 2 Linguagem: Inglês

1938-5447

Bradley C. Livezey,

Genetic diversity and population structure

A cladistic analysis of the stiff-tailed ducks (Anatidae: Oxyurini) was con- ducted using 92 morphological characters. The analysis produced one minimum-length, completely dichotomous phylogenetic tree of high consistency (consistency index for infor- mative characters, 0.74). Monophyly of the tribe was supported by 17 unambiguous syna- pomorphies. Within the tribe, Heteronetta (1 species) is the sister-group of other members; within the latter clade (supported by 2 1 unambiguous synapomorphies), Nomonyx (1 species) is the sister-group of Oxyura (6 species) + Biziura (I species). The latter clade is supported by 10 unambiguous synapomorphies. Monophyly of Oxyuru proper is supported by three unambiguous synapomorphies. All branches in the shortest tree except that uniting Oxyuva, exclusive of jumaicensis, were conserved in a majority-rule consensus tree of 1000 boot- strapped replicates. Biziuru and (to a lesser extent) Heteronetta were highly autapomorphic. Modest evolutionary patterns in body mass, reproductive parameters, and sexual dimorphism are evident, with the most marked, correlated changes occurring in Heteronetta and (es- pecially) Biziura. The implications of these evolutionary trends for reproductive ecology and biogeographic patterns are discussed, and a phylogenetic classification of the tribe is presented. Received 27 April 1994, accepted 10 Nov. 1994. The stiff-tailed ducks (Anatidae: Oxyurini) include some of the most distinctive species of waterfowl; among its members are the only obligate nest-parasite (Black-headed Duck; Heteronetta atricapilla) and the spe- cies showing the greatest sexual size dimorphism (Musk Duck; Biziuru lobz Johnsgard 1962, 1978; Weller 1968; Livezey 1986). Members of the Oxyurini are foot-propelled diving birds (Townsend 1909, Brooks 1945, Tome and Wrubleski 1988) and range in diving ability from the largely surface-feeding Black-headed Duck to the highly specialized Musk Duck (Raikow 1970, 1973; Livezey 1986). Stiff-tailed ducks generally inhabit freshwater lakes and marshes, typically construct over-water nests, and occur in most major land areas worldwide (Delacour 1959; Weller 1964a-d; Johnsgard 1978). Since the reclassification of the White-backed Duck (Dendrocygninae: Thalassornis leuconotus) on behavioral and morphological grounds (Johnsgard 1967; Raikow 1971; Livezey 1986, 1995), systematic contro- versies concerning the stiff-tailed ducks have focused on the tribal posi- tion of the Black-headed Duck, currently considered to be a comparatively primitive member of the Oxyurini (e.g., Salvadori 1895; Phillips 1925, 1926; Peters 1931; Boetticher 1942, 1952; Delacour and Mayr 1945; Ver-