Proposal (162) to South American Classification Committee
Treat Heliangelus micraster and H. exortis as conspecific
This proposal would lump two forms regarded as conspecific in most literature on South American birds through most of the latter half of the 20th century, although some recent literature departs from this view. We currently treat them as separate species.
Heliangelus micraster and H. exortis are two rather small sunangels that differ from most of their congeners in that the males lack a pale band between the gorget and the duller green posterior underparts, having instead an area of flashing green. The most conspicuous difference between them is the gorget color of the males: some shade of purple in exortis, orange in micraster. They were considered separate species by Cory (1918) and Peters (1945). H. exortis is monotypic over its range from N Colombia to NE Ecuador, whereas micraster includes two subspecies: the nominate in SE Ecuador and cutervensis in NE Peru, distinguished by the latter's more red-orange gorget in males and paler green coloration overall.
Zimmer (1951) proposed that micraster be considered conspecific with exortis because the extremes of variation (chiefly in male gorget color) in a long series of the latter showed approach to (but not overlap with) the colors of micraster. This was followed by Meyer de Schauensee (1966) and Sibley & Monroe (1990). However, Bleiweiss (1992) dissented, noting the great degree of individual variation in the gorgets of females in all populations of exortis, whereas females of micraster showed a different pattern with little variation. Also, the distributions of the two approached much more closely in E Ecuador than had been realized by Zimmer, without evidence of intergradation. This was followed with no substantive comments by Schuchmann (1999). Likewise, Ridgely & Greenfield (2001) split the two, considering Zimmer's arguments simply "unconvincing" but providing more details on the close approach of the two without evidence of intermediates, based on recent sightings and specimens.
Although Zimmer (1951) did examine a large series of specimens of exortis in particular, his analysis is deficient on one critical point: he fails to note the geographic provenance of the specimens showing approach to micraster. Only if such specimens were to be concentrated in the southern extreme of the range of exortis could they be taken as evidence for conspecificity of the two, but there is no indication of this in his paper (and it would have been a detail hard to overlook). Indeed, since the great majority of his exortis were from Colombia, it would seem not unlikely that many of his micraster-like specimens were from there as well in the absence of any indication to the contrary. In fact, three of an extensive series of males of exortis from the Cordillera Oriental of Colombia do show orangish flashes from the gorget in certain lights. Zimmer also noted that in certain respects these males resemble the distant cutervensis more than the more nearly adjacent micraster itself. All this strongly suggests that there is no geographic structure to the variation in exortis to indicate gene flow or intergradation. The variability in gorget color in exortis noted by Zimmer is best considered simply individual variation, probably corresponding to a similar (or greater) range of variation in the gorgets of the females as noted by Bleiweiss.
I therefore conclude that the evidence for conspecificity of exortis and micraster is deficient and that they are best treated as separate species, and recommend a NO vote on this proposal, i.e. continue to treat them as separate species.
(If this proposal passes, there is an issue regarding the English name to be treated in a subsequent proposal).
BLEIWEISS, R. 1992. Widespread polychromatism in female sunangel hummingbirds (Heliangelus: Trochilidae). Biol. J. Linnean Soc. 45: 291-314.
Meyer de Schauensee 1966
Ridgely & Greenfield 2001
Sibley & Monroe 1990
Gary Stiles, January 2005
Comments from Remsen: "NO. As Gary notes, evidence favors treatment as two species ... or at least they should be maintained that way until contradictory evidence published."
Comments from Pacheco: "NO. Diante do quadro atual, tratar os presentes táxons como conspecíficos seria incoerente."
Comments from Robbins: "NO for reasons detailed in Gary's proposal."
Comments from Nores: "NO. Pienso que la razones dadas por Stiles son suficientes para considerarlas especies separadas. El color de la garganta es demasiado diferente para que sean subespecies, lo cual es evidente que varía individualmente y no gradualmente."
Comments from Jaramillo: "No. Evidence for a lump deficient."