Taxonomic revision of Myrmeciza (Aves: Passeriformes: Thamnophilidae) into 12 genera based on phylogenetic, morphological, behavioral, and ecological data
Isler, Morton L.
Bravo, Gustavo A.
Brumfield, Robb T.
Zootaxa
2013
3717
4
469
497
6RTBG
[151,252,618,644]
Aves
Thamnophilidae
Myrmeciza
Animalia
Passeriformes
20
489
Chordata
species
longipes
Biogeography.—Most species are Amazonian in distribution. However, longipesis patchily distributed west of the Andes and east of the Andes north of the Amazon, nudicepsand immaculataare trans-Andean, and the ranges of Pyriglenaspecies extend to both Pacific slope of the Andes and the Atlantic coast of Brazilsouth to northern Argentina. Most species have limited geographic ranges and are allopatric within clades except myotherinusand leucophryswhose ranges are extensive and overlap most other cis-Andean species. Also, longipesis sympatric only with leucophrysin the Guianan region; fortisis sympatric with the melanocepsclade; and immaculatais only narrowly sympatric with nudiceps, as are Pyriglenaand Percnostolaspecies with fortis, melanoceps, and goeldii. Plumage.— Pyriglena, Percnostola, and Myrmoborus species exhibit distinctive plumage features. Males of all species are black, gray, and white although plumages of some Pyriglenasubspecies also include dark chestnut. Males of Pyriglenaspecies have bright red eyes and white interscapular patches. The gray males of the two Percnostolaspecies have distinctive black throats and dark crowns. The gray males of most species in the Myrmoborusclade have a distinctive face and throat patch edged with a white or pale gray superciliary although those of melanurusand lophotesare altogether black or blackish. Females are primarily brown with the following features: Pyriglenaspecies have blackish tails; females of Percnostolaspecies are gray or cinnamon-gray above; most females in the Myrmoborusclade have black or blackish lores and ear-coverts forming a distinctive patch although these are lacking in one lugubrissubspecies and lophotes. The distinct plumage of longipesis distinguished by a number of characters including the rufous upperparts of males and the black subapical spots on wing coverts of females and most male subspecies. Males of nudicepsand the immaculataand melanocepsclades are black or blackish with bare bluish periorbital patches (extending to the forecrown in nudiceps); the presence of white patches differs among species except that immaculataand fortisshare mostly concealed white patch at the bend of wing. Females of nudicepsand the immaculataand melanocepsclades are yellowish-brown to reddishbrown with bare bluish periorbital patches and pale wing covert edges (variable), the presence and extent of black or gray differing among species. Morphometrics.—The most notable differences in measurements are the large sizes of species in the immaculataand melanocepsclades ( Table 2). However, these two clades differ in opposing directions in wing and tail lengths, leading to a large difference in tail/wing ratio ( Table 3). Other noteworthy differences in size involve the relatively short bills and long tails of Pyriglenaspecies which result in significant differences in bill length/total length and tail length/wing length ratios with the myotherinusclade, nudiceps, Percnostolaspecies, and the melanocepsclade.` Loudsongs.—Loudsongs of all species are structurally similar, consisting of a 2–4 second series of similar notes (typically an inverted V or U shape, less often down-slurred) that are repeated in a regular pattern (only species in the immaculataclade show a slight shift in pattern). Habitat.—The most distinct typesof habitat are occupied by longipeswhich is found in semideciduous and gallery forest, second growth woodland, and shrubby borders. Other species principally occur in evergreen forests, although some Pyriglena leuconotasubspecies occupy deciduous forests. Nearly all species in the longipesclade show a predilection for dense tangles and thickets, especially in forest openings and borders. Specialties include water-related habitats for some Myrmoborusspecies, sandy soil forest for Percnostolaspecies, and floodplain and transitional forest for the melanocepsclade and lophotes. Foraging behavior.—All species forage primarily on the ground and on low substrates mostly within 1–2 mof the ground. All species, except perhaps for lophotesand arenarum, follow army ant swarms to some extent. Most are considered “regular” ant-followers, and fortisis considered an obligate follower. Tail and wing movements.—All species ( arenarumunknown) pound the tail downward and slowly raise it to horizontal or slightly higher. Nest architecture.—Except for longipesall species ( arenarumunknown) build domed or partially domed nests atop leaf litter on the ground or to 1 moff the ground among fallen limbs or leaf rachides of understory palms (recent additions: Greeney et al. 2004, Lebbin et al. 2007). Myrmeciza longipesbuilds an open cup just off the ground; said to be placed on supports rather than slung from them.
Discussion.—Consistency of behavioral characteristics, including loudsong structure, tail and wing movements, and foraging behavior, reinforces the molecular finding of common ancestry for species in the longipesclade. An exception is Myrmeciza longipeswhich differs from other species in the clade in its nest architecture and habitat preferences. Existing genera within the group, Gymnocichla, Myrmoborus, Pyriglenaand Percnostola, have, however, long been recognized as distinct in plumage and morphometrics from each other and from longipes, and placing them in a single genus is clearly inappropriate. This leaves questions of lophotesand the immaculataand melanocepsclades. Regarding lophotes, the phylogeny places it within Myrmoborus, and its plumage resemblance to Myrmoborus melanurus(not noted previously in the literature) became obvious after the genetic study showed that they are sisters. The morphologically similar immaculataand melanocepsclades form a polytomy with Percnostola( Figs. 1and 2) and, therefore, cannot be placed in the same genus. The two clades differ principally in tail length and wing length and consequently in wing/tail proportions. Given the choice of uniting the immaculataand melanocepsclades with the morphologically dissimilar Percnostolaor recommending that they be placed in three genera, the latter course is most consistent with previous generic decisions in the Thamnophilidae, such as the purely morphological basis for the maintenance of Gymnocichlaand Pyriglena. Taxonomic Recommendations.—We recommend that Myrmeciza longipesbe maintained in a monotypic genus, that Gymnocichla, Myrmoborus, Pyriglena, and Percnostolabe maintained as genera, and that Percnostola lophotesbe transferred to the genus Myrmoborus. We also recommend that species in the immaculataand melanocepsclades be considered distinct from the foregoing and that they be placed in different genera given their uncertain phylogenetic relationship and the morphometric characters that distinguish them.