Isleria guttata (Vieillot, 1825)

Chesser, R. Terry, Isler, Morton L., Santana, Antonita, Latch, Emily K., Stryjewski, Katherine Faust, Reed, Jennifer, Naka, Luciano N., Fleischer, Robert C. & Aleixo, Alexandre, 2025, Comparative phylogeographic patterns in three pan-Amazonian antwren lineages (Aves: Passeriformes: Thamnophilidae: Myrmotherula and Isleria), Zootaxa 5722 (1), pp. 1-44 : 10

Rufous-bellied Antwren Isleria guttata and Plain-throated Antwren I. hauxwelli

Analyses of I. guttata-hauxwelli distinguished five main clades separated by at least 2.5% sequence uncorrected divergence ( Table 1; Fig. 8 ). One clade corresponds to I. guttata , which is sister to all other clades.Within I. hauxwelli , one of the clades corresponds to subspecies hellmayri, but the other clades are not congruent with the other subspecies, suffusa and hauxwelli ( Fig. 9 ). The clade that includes all individuals within the described distribution of suffusa, north of the upper Amazon and Marañón, also includes individuals south of the Marañón and west of the Ucayali, in the western part of the described range of nominate hauxwelli ; we call this clade hauxwelli- W rather than suffusa because the type locality of hauxwelli (the name has priority over suffusa) is within the distribution of this composite group. Two other clades, which we call hauxwelli- C and hauxwelli -E, occupy the majority of the described range of nominate hauxwelli . The distribution of hauxwelli -C extends east of the Ucayali to the lower Madeira and across the upper Madeira as far east as the Rio Teles Pires. This clade forms two shallow subclades ( hauxwelli- C-W and hauxwelli- C-E) divided by the upper Madeira-Mamoré and separated by 0.6% sequence divergence. Both subclades of hauxwelli -C show additional structure, but this is not geographically structured. Individuals east of the extreme lower Madeira, on both sides of the Tapajós and east of the Teles Pires in the Tapajós-Xingu interfluvium, form major clade hauxwelli- E. This clade also consists of two subclades, in this case 0.9% divergent; these groups are separated by the Tapajós, one subclade northwest of the river ( hauxwelli- E-N) and the other southeast ( hauxwelli- E-S). Main clades in this species complex are largely delineated by rivers: the Amazon-Negro, separating I. guttata from I. hauxwelli ; the Xingu, separating hellmayri from all forms of hauxwelli ; the Teles-Pires (and perhaps lower Madeira), separating hauxwelli- E from hauxwelli -C and -W; and the Amazon-Ucayali, separating hauxwelli -C from hauxwelli -W. The Madeira and Tapajós separate subclades, except perhaps for the extreme lower Madeira, which may separate hauxwelli- C and hauxwelli- E. Support for all clades and subclades was strong: posterior probabilities were all 1.0, except for 0.90 for hauxwelli -C-W, and bootstrap values were 80–100%. Relationships among clades were strongly supported except for the sister relationship between hauxwelli -E and hauxwelli -C/ hauxwelli -W, which received 0.97 posterior probability but less than 50% bootstrap. The deepest split within the tree was 7.8% uncorrected divergence, separating currently recognized species I. guttata and I. hauxwelli .

Figures

FIGURE 8. Maximum clade credibility tree for Isleria guttata and I. hauxwelli from the BEAST (Bouckaert et al. 2014) analysis. Individuals are color-coded by main clades but also identified by subspecies and subclade. Note the intermixing of samples of suffusa and hauxwelli in Main Clade 2: samples of suffusa are marked with an asterisk. The geographical area encompassed by this clade includes the type locality of hauxwelli, and this clade is identified as hauxwelli because this name has priority over suffusa. Numbers above branches indicate posterior probabilities and ML bootstrap support values at the corresponding nodes. Arrows at nodes and corresponding text indicate rivers that separate clades united by the nodes.

FIGURE 9. Map showing the distributions of main clades and subclades of Isleria guttata and I. hauxwelli. Main clades are color-coded to match FIGURE 8; subclades within hauxwelli-C and hauxwelli-E are separated by the dashed lines along the Mamore and the Tapajós, respectively. Solid dots = tissue locations; heavy lines surround geographic ranges as confirmed by the molecular analysis. Refer to FIGURE 3 for names of locations of tissue samples. Base map layers sourced from Esri (Redlands, California).