A phylogenetic analysis of the whistling and white-backed ducks (Anatidae: Dendrocygninae) using morphological characters

Abstract

A phylogenetic analysis of the eight species of whistling-duck (Dendrocygna) and the White-backed Duck (Thalassornis leuconotus) was performed using 68 characters of the skeleton, trachea, and natal and definitive integument. Three shortest trees were found, each having a length of 91 and a consistency index of 0.766 (excluding uninformative characters). Monophyly of Dendrocygna + Thalassornis was supported by three unambiguous synapomorphies, and monophyly of Dendrocygna by eight unambiguous synapomorphies. The three shortest trees supported two major clades within Dendrocygna, each supported by three synapomorphies: (1) D. autumnalis + D. viduata; and (2) the other six species of Dendrocygna. Within the latter, the three shortest trees defined two groups: (1) D. guttata + D. arborea (supported by three synapomorphies); and (2) an unresolved trichotomy (supported by one unambiguous synapomorphy) involving D. eytoni, D. bicolor, and the clade D. arcuata + D. javanica (the last two united by three synapomorphies). A majority-rule consensus tree of 1000 bootstrapped replicates confirmed all of the branches common to the three equally parsimonious trees. All species of Dendrocygna and (especially) Thalassornis were highly autapomorphic. Mapping of selected ecomorphological parameters on the trees revealed evolutionary patterns in body mass, egg mass, relative clutch mass, and diving habit, with lesser trends in preferred nest site, perching habit, and diel activity pattern. A phylogenetic classification of the group is presented and related systematic and biogeographic issues are discussed.