Underestimated Neotropical diversity: Integrative taxonomy reveals two unrelated look-alike species in a suboscine bird (Pachyramphus albogriseus)

Abstract

ABSTRACT We applied an integrative taxonomic framework to evaluate the systematics of the Neotropical Black-and-white Becard (Pachyramphus albogriseus Sclater 1857). Combining phylogenomic (ultraconserved elements), morphological, and vocalization data, we confirmed that this species is polyphyletic; some individuals form a clade sister to P. polychopterus and should be afforded species rank as P. salvini Richmond 1899 (Slender-billed Becard), whereas the remaining subspecies of P. albogriseus (Broad-banded Becard) are sister to P. major. We found that P. salvini differs from P. albogriseus in song, color of the lores, wing-bar width, body size, and bill width. Whereas P. albogriseus occurs in montane forest in Costa Rica and Panama (ssp. ornatus) and along the eastern slope of the Andes from northern Venezuela to southern Peru (ssp. albogriseus), P. salvini is found in the lowlands from Pacific Colombia south to northwest Peru and in the Río Marañón drainage. The latter also occurs, possibly only seasonally, along the eastern slope of the Andes, where the two species' ranges approach closely. We treat P. a. guayaquilensis Zimmer 1936 as a junior synonym of P. salvini Richmond 1899, and P. a. coronatus Phelps and Phelps 1953 as a junior synonym of P. a. albogriseus Sclater 1857. This study provides a striking example of a major problem for comparative biology: underestimated and mischaracterized diversity. We argue that there are likely many more cases like this awaiting discovery. LAY SUMMARY An integrative taxonomic framework reveals that two subspecies in the Black-and-white Becard (Pachyramphus albogriseus) are not closely related to that species. Two non-sister species differing subtly in plumage but more clearly in morphology and vocalizations are uncovered: Slender-billed Becard (P. salvini) and Broad-banded Becard (P. albogriseus). The two species are largely allopatric but P. salvini occurs, possibly only seasonally, on the east slope of the Andes in eastern Ecuador, and north and central Peru, in close proximity to P. albogriseus. Little data indicate spatial overlap between P. salvini (usually to the west, at higher altitude in dry to humid areas) and P. albogriseus (usually to the east, at lower altitude often in undisturbed, humid forest). Systematic work integrating phenotypic, genomic, and vocalization data, along with dense geographic sampling will increase the probability of detecting unrecognized species in the future. We highlight a major problem facing biodiversity science and comparative biology in general; species diversity remains underestimated and mischaracterized, even for well-inventoried groups like birds. RESUMEN Aplicamos un marco de taxonomía integradora para evaluar la sistemática de un ave neotropical, el Cabezón Blanco y Negro, Pachyramphus albogriseus Sclater 1857. Combinando datos filogenómicos (elementos ultraconservados), morfológicos y vocales, confirmamos que esta especie es polifilética; algunos individuos formaron un clado hermano a P. polychopterus y deben ser elevados al rango de especie como P. salvini Richmond 1899 (Cabezón Pico Fino), mientras que las restantes subespecies de P. albogriseus (Cabezón Bandas Anchas) son hermanas de P. major. Encontramos que P. salvini difiere de P. albogriseus en canto, color de la región loral, ancho de filetes alares, tamaño corporal y ancho del pico. Mientras que P. albogriseus habita bosques montanos en Costa Rica y Panamá (ssp. ornatus) y a lo largo de la ladera este de los Andes desde el N de Venezuela al S de Perú (ssp. albogriseus), P. salvini se encuentra en tierras bajas desde el Pacífico de Colombia hacia el sur hasta el NO de Perú y en el Valle del Río Marañón. Esta última especie también ocurre, quizás sólo estacionalmente, a lo largo de la ladera este de los Andes, donde las distribuciones de ambas especies se aproximan estrechamente. Tratamos a P. a. guayaquilensis Zimmer 1936 como un sinónimo junior de P. salvini Richmond 1899 y a P. a. coronatus Phelps y Phelps 1953 como un sinónimo junior de P. a. albogriseus Sclater 1857. Este estudio muestra un impactante caso de un problema mayor para la biología comparada: la subestimación y caracterizatión errónea de la diversidad. Proponemos que existen posiblemente mucho más casos como éste aguardando a ser descubiertos.