Population genetics and key phenotypic variability does not support different subspecies of Yellow-throated Woodland Warbler Phylloscopus ruficapilla within the Eastern Cape, South Africa

Abstract

Two subspecies of the Yellow-throated Woodland Warbler Phylloscopus ruficapilla (family Phylloscopidae) have been recognised in South Africa based on the extent and intensity of yellow colouration. Our previous multi-locus population genetic survey across much of the Eastern Cape and southern KwaZulu-Natal provinces, conducted from 2017 to 2023, revealed a single homogenous regional population. That finding, derived from 93 individuals sampled from nine sites—six northeast of the Great Kei River (n = 72) and three to the southwest (n = 21)—did not support a subspecies boundary near the Great Kei River. Here, using 188 publicly archived photographic records for this species in South Africa, we show that the phenotypes of both subspecies are present on either side of this divide. The observed genetic homogeneity and lack of clear phenotypic vicariance suggest that P. ruficapilla is more dispersive than currently appreciated, and that the plumage-based subspecies may not represent significant population-level differences.