A team of ornithologists from Brazil and Finland has discovered a cryptic new species of flatbill flycatcher living in the Amazonian lowlands.
The olivaceous flatbill (Rhynchocyclus olivaceus). Image credit: Hector Bottai / CC BY 4.0.
Flatbill flycatchers are members of the genus Rhynchocyclus in the exclusively New World family Tyrannidae.
Four known species in the genus are distributed from southern Mexico to northeastern Bolivia, eastern Venezuela, and Brazil.
“Rhynchocyclus currently includes four species: the olivaceous flatbill (Rhynchocyclus olivaceus), the eye-ringed flatbill (Rhynchocyclus brevirostris), the Pacific flatbill (Rhynchocyclus pacificus) and the fulvous-breasted flatbill (Rhynchocyclus fulvipectus),” said Dr. Alexandre Aleixo from the Finnish Museum of Natural History at the University of Helsinki and colleagues.
“Two of these are monotypic (Rhynchocyclus pacificus and Rhynchocyclus fulvipectus), and the other two are polytypic (Rhynchocyclus olivaceus and Rhynchocyclus brevirostris).”
“As the most widespread species in the complex, all nine subspecies of Rhynchocyclus olivaceus are very similar to each other, with a remarkable constancy in morphometric characters and plumage color patterns, which evidences their cryptic nature.”
“All are large-headed, and flat-billed; with whitish eye rings; upper parts olive-green; wings and tail dark brown with olive-green (edged feathers); lower parts grayish-green, striated with yellowish; center of the abdomen yellowish; iris dark-brown; maxilla blackish; mandible white; and tarsi bluish-gray.”
“However, unlike morphology, vocal patterns among subspecies of Rhynchocyclus olivaceus appear to have conspicuous differences.”
The authors analyzed DNA and morphological data from museum specimens of Rhynchocyclus species and subspecies as well as their song recordings.
The results strongly suggest the existence of a previously unknown cryptic species in the genus.
“The new species is named the cryptic flatbill (Rhynchocyclus cryptus) after its remarkable morphological cryptic nature, which strongly contrasts with its high levels of vocal and genetic differentiation, two characteristics which probably allow for the sympatry with Rhynchocyclus guianensis throughout its range,” the researchers explained.
The new species prefers seasonally flooded floodplain forests (várzea), including degraded patches close to human settlements.
It can be found south of the Amazon River and on islands along its main channel, from both banks of the Madeira River in the states of Amazonas and Acre in Brazil, westwards to the Marañon River in Peru, and southwards to north/central Bolivia in the Mamoré and likely Beni drainages in the departments of Cochabamba and possibly Beni, La Paz and Pando.
“The main threats for Rhynchocyclus cryptus are deforestation caused by rapid progress of livestock farms, monocultures and implementation of large hydroelectric dams on the Madeira River, which affect the flow of sediments supporting seasonally flooded forests along its banks,” the scientists said.
“However, most parts of the species’ distribution are in areas of limited access and within conservation units.”
“The extent of occurrence of Rhynchocyclus cryptus based on the area covered by our genetic sampling is estimated as 704,000 km2, hence not reaching the threshold to be treated as Vulnerable,” they added.
“Therefore, the species should be treated as Least Concern according to IUCN guidelines.”
The discovery of the cryptic flatbill is described in a paper published in the journal Zoologica Scripta.
_____
Carlynne C. Simões et al. Integrative taxonomy of Flatbill Flycatchers (Tyrannidae) reveals a new species from the Amazonian lowlands. Zoologica Scripta, published online November 10, 2021; doi: 10.1111/zsc.12519
