Spectacled Tyrannulet Zimmerius improbus
Version: 2.0 — Published November 30, 2018
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Spectacled Tyrannulet comprises two recognized subspecies as well as several populations that may also merit recognition as subspecies:
nominate improbus, described as Tyranniscus improbus Sclater and Salvin 1871. Type locality Mérida, Venezuela and Sierra de Ocaña, Colombia; restricted to Mérida by Sclater (1888; see also Warren and Harrison 1971).
Occurs in the Andes of Venezuela (except for the area occupied by tamae), in eastern Táchira, Merida, and Barinas.
subspecies tamae, described as Tyranniscus vilissimus tamae Phelps and Phelps 1954. Type locality Páramo de Tamá, 2400 m, Táchira, Venezuela.
The range traditionally attributed to tamae includes the Sierra Nevada de Santa Marta (Magdalena, Colombia), the Sierra de Perijá on the Colombian/Venezuelan border, and Zulia and southern Táchira in the Andes of Venezuela (e.g. Traylor 1979). The geographic region encompasses three genetically distinct populations, however, and so may represent three taxa (Rheindt et al. 2013); consequently, the range of tamae sensu stricto is limited to the Eastern Andes of Colombia in Norte de Santander and the adjacent Andes of Venezuela (Táchira). Samples from the Serranía de Perijá, of Colombia and Venezuela, and from the Sierra Nevada de Santa Marta, Magdalena, Colombia are sister to each other; this pair in turn is sister to improbus from the Andes of Venezuela (eastern Táchira) and to tamae, which are sister to each other. These phylogenetic relationships suggest that the populations from the Santa Martas and from the Perijá each merit recognition as separate subspecies, although plumage and vocal differences have not yet been noted.
Subspecies tamae is similar to improbus, but "differs in darker, more dusky crown; lores and superciliary stripe white, untinted with yellowish; breast grayer with less yellowish brown tinge; abdomen and under tail-coverts paler yellow" (Phelps and Phelps 1954).
All species of Zimmerius formerly were classified in Tyranniscus, but Traylor (1977) partitioned Tyrannicus into two groups; a few species were assigned to Phyllomyias (Black-capped Tyrannulet Phyllomyias nigrocapillus, Ashy-headed Tyrannulet Phyllomyias cinereiceps, and Tawny-rumped Tyrannulet Phyllomyias uropygialis), and for the remaining species, including improbus, Traylor erected the new genus Zimmerius. The genus Zimmerius is monophyletic (Tello et al. 2009; Rheindt et al. 2013).
Zimmerius improbus has been recognized as a separate species by various authorities as early as Hellmayr (1927), and has had several different English names, such as Specious Tyrannulet or Mountain Tyrannulet. Many later authors classified improbus and tamae as subspecies within a polyphyletic Paltry Tyrannulet Zimmerius vilissimus (e.g., Phelps and Phelps 1954, Meyer de Schauensee 1966, Traylor 1979). Rheindt et al (2013), which showed that this broadly defined Paltry Tyrannulet was comprised of four clades, most of which are not closely related with the genus: Zimmerius vilissimus/parvus (Guatemalan Tyrannulet/Mistletoe Tyrannulet,) Zimmerius petersi (Venezuelan Tyrannulet), and Zimmerius improbus (including tamae); consequently, each of these now is recognized as a separate species. Spectacled Tyrannulet the basal member of a large group of species that includes Zimmerius chrysops (Golden-faced Tyrannulet), Zimmerius viridiflavus (Peruvian Tyrannulet), Zimmerius bolivianus (Bolivian Tyrannulet), Zimmerius gracilipes (Slender-footed Tyrannulet), and Zimmerius petersi.