Phylogenetic relationships of the hoatzin, an enigmatic South American bird.

Abstract

The hoatzin (Opisthocomus hoazin) lives in the humid lowlands of northern and central South America, often in riparian habitats. It is a slender bird -65 cm in length, brownish with lighter streaks and buffy tips to the long tail feathers. The small head has a ragged, bristly crest of reddish-brown feathers, and the bare skin of the face is bright blue. It resembles a chachalaca (Ortalis, Cracidae) in size and shape, but its plumage and markings are similar to those of the smaller guira cuckoo (Guira guira). The hoatzin (pronounced Watson) has been a taxonomic puzzle since it was described in 1776. It usually has been viewed as related to the gallinaceous birds, but alliances to other groups have been suggested, including the cuckoos. We present DNA sequence evidence from the 12S and 16S rRNA mitochondrial genes, and from the nuclear gene that codes for the eye lens protein, aA-crystallin. The results indicate that the hoatzin is most closely related to the typical cuckoos and that the divergence occurred at or near the base of the cuculiform phylogenetic tree.

α-Crystallin Sequences Support a Galliform/Anseriform Clade

“…Maximum parsimony analysis of tandemly combined a-and b-hemoglobin sequences placed a clade consisting of galliforms, songbirds, and parrots as a sister-group to Anseriformes; in this study, however, the neognathous storks were the first offshoot of the avian lineage (Czelusniak et al, 1990). A tree based on mitochondrial 12S and 16S rRNA gene sequences indicated a sister-group position of chicken and duck, albeit with a very low confidence probability value (Hedges et al, 1995).…”

“…aA-Crystallin amino acid sequences had been unable to resolve the galliform/anseriform/other neognath trichotomy (Stapel et al, 1984), but a 146-bp fragment of the aA-crystallin gene placed the duck as a sister-group of a galliform clade represented by chicken and silver pheasant (Lophura nycthemera), although with a low confidence probability value (Hedges et al, 1995). This prompted us to investigate whether longer aA-crystallin nucleotide sequences would give more conclusive evidence as to the position of Galliformes and Anseriformes in avian phylogeny.…”

Second report on chicken genes and chromosomes 2005

“…It feeds on young leaves and twigs of marsh plants and has a large muscular crop for fermentation. Most phylogenetic analyses have placed the hoatzin in the Galloanserae, but DNA hybridization studies and DNA sequence studies have agreed that it is a neoavian species (Sibley and Ahlquist, 1990;Hedges et al, 1995;Hughes and Baker, 1999;Sorenson et al, 2003). However, its particular relationship within Neoaves has not yet been resolved.…”

Bacterial Community in the Crop of the Hoatzin, a Neotropical Folivorous Flying Bird

“…At a purely mechanical level, crop enlargement can require sternal modifications that restrict flight capabilities (16,18). Moreover, the adult hoatzin is the smallest animal among known foregut fermenters, with an average weight of only 700 g. The minimum body size for a mammal with foregut fermentation is ϳ3 kg (6); a small body size restricts the luminal volume needed for fermentation, and energy demand scales to metabolic weight (w 0.75 ) (26).…”