Taxonomic status of the Liberian Greenbul Phyllastrephus leucolepis and the conservation importance of the Cavalla Forest, Liberia

Abstract

The Liberian Greenbul Phyllastrephus leucolepis is known only from the Cavalla Forest, Liberia, where it was seen between 1981 and 1984 but has not been found since the collection of the type, and only, specimen. It is similar to the common and widespread Icterine Greenbul P. icterinus, from which it differs primarily in having white subterminal spots on the wing coverts and all flight feathers. Its validity as a distinct species has been questioned but left unresolved. This paper describes the first genetic study of the Liberian Greenbul, to attempt to determine whether it is a distinct species, a plumage variant of Icterine Greenbul, or a hybrid. Total genomic DNA was isolated independently by two separate laboratories from the type specimen, as well as from Icterine and Whitethroated Greenbuls P. albigularis sampled close to the type locality in Liberia. Mitochondrial and nuclear DNA was sequenced and compared to that of Icterine and other greenbul species from Liberia and elsewhere. Sequence analysis of three mitochondrial genes and one nuclear gene showed that the Liberian Greenbul is not a hybrid but falls within the range of intraspecific genetic variation observed in the Icterine Greenbul. Reasons for this are discussed, but the most likely explanation is that the Liberian Greenbul represents a plumage variant of the Icterine Greenbul. The alternative possibilities that the Liberian Greenbul represents a distinct species which only recently diverged or has ongoing gene flow with the Icterine Greenbul cannot be formally refuted. Conservation implications for the Cavalla Forest are discussed.

Investigation of the status of the enigmatic White‐chested TinkerbirdPogoniulus makawaiusing molecular analysis of the type specimen

“…Such mutations may also explain the distinct plumage pattern in what was described as Liberian Greenbul Phyllastrephus leucolepis , another localized sub‐Saharan African form for which there was just a single specimen collected, which was recently found to be phylogenetically nested within Icterine Greenbul Phyllastrephus icterinus (Collinson et al . ).…”

What's in a name? Nomenclature for colour aberrations in birds reviewed

“…With recent DNA work many of these 'new species' have been unmasked (e.g. Collinson et al 2017, Kirschel et al 2018, Schweizer et al 2020, see also van Grouw 2010, Figure 22. Dilution in Eurasian Jackdaw Corvus monedula, Terschelling, the Netherlands, March 2014; because corvids possess only one form of melanin (eumelanin), it is impossible to determine if this form of Dilution would affect both melanins if present (© Bert Bruggeman) 2017 for more examples).…”

Full Issue

“…With recent DNA work many of these 'new species' have been unmasked (e.g. Collinson et al 2017, see also van Grouw 2010, 2017 for more examples). Hachisuka (1926), in his description of the melanistic Common Pheasant Phasianus colchicus, which he correctly recognised as an aberration (mutation), highlighted the problem and noted that such cases would always prove misleading unless a definitive nomenclature was developed.…”