Isleria hauxwelli clarior ( Zimmer, 1932 )

Isler, Morton L., Chesser, R. Terry, Stryjewski, Katherine Faust & Whitney, Bret M., 2025, Systematics of three pan-Amazonian antwren lineages (Aves: Passeriformes: Thamnophilidae: Myrmotherula and Isleria), Zootaxa 5722 (1), pp. 45-78 : 70

Isleria hauxwelli clarior ( Zimmer, 1932) , subspecies resurrected

Includes the populations designated hauxwelli- C and hauxwelli- E in the analysis.

Diagnosis. Song differs from that of I. h. hauxwelli in lacking frequency modulation of notes. Plumage differs from that of I. h. hellmayri by having a white interscapular patch.

Distribution. South of the Amazon River from the mouth of the Rio Xingu, Brazil, west to the mouth of the Rio Ucayali, Peru; thence south, east of the Rio Ucayali from its mouth to the vicinity of the Rio Cushabatay, Peru; thence south, east of the Andes, to La Paz, Bolivia; thence east, north of Amazonian forest limits, to the Rio Xingu, Brazil.

Remarks. Although the study populations included in this subspecies exhibited variation in vocal and morphological characters, non-overlapping vocal differences among populations did not meet our criteria for diagnosability. With the assembly and analysis of additional recordings and specimens, some study populations are likely to warrant taxonomic recognition. This supposition is supported by the branching patterns and mtDNA distances in the phylogeographic results. Further vocal analysis should emphasize Song frequency. Frequency measurements suggested that there might be diagnostic differences among hauxwelli populations. Frequency was typically higher east than west of the Tapajós/Teles Pires. Differences were especially noticeable across the Teles Pires at Alta Floresta and across the lower Tapajós. However, Songs of female-plumaged birds appear to be higherpitched than those of males, and such analyses should control for sex. This subspecies differs by 2.5–3.0% in mtDNA from other subspecies of I. hauxwelli , but the genetic data indicate that hauxwelli- C is more closely related to hauxwelli- W than to hauxwelli- E. Nuclear data would provide further insight on the discrepancy between the song and mtDNA data.