Willisornis poecilinotus, GRISEIVENTRIS

Quaresma, Tânia Fontes, Cronemberger, Áurea A., Batista, Romina & Aleixo, Alexandre, 2022, Diversification and species limits in scale-backed antbirds (Willisornis: Thamnophilidae), an Amazonian endemic lineage, Zoological Journal of the Linnean Society 196 (4), pp. 1408-1430 : 1420-1421

WILLISORNIS POECILINOTUS GRISEIVENTRIS

( VON PELZELN, 1869)

Taxonomy

Genetic lineages sharing plumage characteristics discussed below are unequivocally assigned to W. p. griseiventris (type locality: Borba, on the right/ eastern bank of the Madeira River; Peters, 1951), distributed in south-eastern Peru, northern Bolivia and south-western Amazonian Brazil, eastwards to the upper Xingu River ( Pulido-Santacruz et al., 2018; Gill et al., 2022).

Plumage attributes

Males similar to those in W. p. poecilinotus . Females pale plain rufous throughout the dorsal region, extending to the forehead and the sides of the head. ‘Dark-light lace’ on the back and wings absent. Throat and ventral region grey. Upper and under tail parts concolorous with the body, but with narrow distinct white terminal edges.

Genetic differentiation

Specimens with the plumage characteristics above belong to a widespread genetic lineage with two major geographic sister groups replacing each other across the Madeira River and referred herein as W. p. griseiventris A and W. p. griseiventris B. These two lineages are completely sorted for their mitochondrial DNA, but less so for the nuclear genes, occurring throughout most of south/central Amazonia, from the upper Juruá River eastward to the headwaters of the Xingu River (Fig. 1).

Plumage variation

We identified a geographic gradient in male plumage colour in W. p. griseiventris A and B running from west to east, with the darkest individuals found in the west (considering the overall body colour) and the palest in the east. Despite this clear trend, major shifts in the overall plumage colour intensity were not correlated with interclade boundaries and the presence of the Madeira River itself.