A Phylogenetic Analysis and Classification of Recent Dabbling Ducks (Tribe Anatini) Based on Comparative Morphology

Abstract

Cladistic analysis of 157 characters of definitive plumages and soft parts, natal plumages, tracheae, and nontracheal skeletons of 59 Anatini (sensu Livezey 1986) provided a phylogenetic hypothesis of high consistency (CI = 0.71, excluding unique autapomorphies) and resolution (tree completely resolved except for two nested trichotomies, a trichotomy within the northern-hemisphere mallards, and the tentative placements of two poorly known species of Anas). Major phylogenetic inferences (lists of three or more taxa are in order of increasing relatedness) include the following: (1) monophyly of the tribe is weakly demonstrated; (2) the tribe comprises three subtribes-Cairineae (Cairina, Pteronetta, Aix), Nettapodeae (Chenonetta, Nettapus), and Anateae (all other genera); (3) subtribe Anateae comprises three "supergenera" (each comprising two genera)-Amazonetta (A. brasiliensis and Callonetta leucophrys), Lophonetta (L. specularioides and Speculanas specularis), and Anas (genera Mareca and Anas); (4) the genus Mareca or wigeons includes six species-capensis, strepera, falcata, sibilatrix, penelope, and americana; and (5) the large genus Anas comprises two weakly supported subgroups or cohorts, the first of which includes two subgenera (mallards [Anas]and blue-winged ducks [Spatula]) and the second includes four subgenera (Australasian teal [Nesonetta], pintails [Dafila], Holarctic teal [Querquedula], and spotted teal [Punanetta]). Other findings include that a sister-relationship exists between Anas sparsa and other mallards, that subgroups of the "true" mallards are largely congruent with biogeographic subdivisions (northern-hemispheric, African, and South Pacific), that the four species of shoveler are monophyletic, that a sister-relationship between the speckled teals (flavirostris and andium) and brown pintails (georgica, acuta, and eatoni) exists, and that A. querquedula is the sister-group to the green-winged teals (formosa, crecca, and carolinensis) and not closely related to the blue-winged ducks. Supplementary data and related theory indicated that (1) interspecific interfertility is a poor indicator of relationship, (2) the phylogenetic species concept provided the most practical definition of terminal taxa, (3) a majority of groups within the Anatini originated in the southern hemisphere, (4) body size, sexual size dimorphism, and egg size are strongly constrained phylogenetically, whereas sexual dichromatism and clutch size are less predictable, (5) biparental attendance of broods is primitive within Anatini, and (6) characters of definitive plumages, natal plumages, tracheae, and skeletons had similar consistencies but attained maximal utility at different levels within the phylogeny, which indicates different rates of character evolution within the tribe.