Leapfrogging revisited in Andean birds: geographical variation in the Tody‐tyrant superspecies Poecilotriccus ruficeps and P. luluae

Abstract

I analysed geographical variation in size, colour and pattern quantitatively in the Rufous‐crowned Tody‐Tyrant Poecilotriccus ruficeps and Lulu Von Hagen’s Tody‐Tyrant P. luluae, two component species of a superspecies inhabiting the northern Andes of South America. The conspicuously bridled P. r. melanomystax, here reported for the first time from the Andes of Venezuela and the Eastern Andes of Colombia, leapfrogs southward over populations of the plain‐headed P. r. ruficeps in the Eastern Andes of Colombia, re‐occurs in the Central Andes of Colombia, leapfrogs over populations of P. r. ruficeps in south‐western Colombia and Ecuador, then ‘re‐appears’ as the similarly bridled P. r. peruvianus in southern Ecuador and northern Peru. In a second example of leapfrogging, the recently described P. luluae from the Eastern Andes of northern Peru is separated from superficially similar populations of P. r. ruficeps by the distribution of P. r. peruvianus. Because of their striking plumage differences and lack of interbreeding, the two bridled forms, P. r. melanomystax and P. r. peruvianus, may together constitute a species separable from the plain‐headed forms, P. r. ruficeps and P. r. rufigenis. Vocally, however, all forms of P. ruficeps are similar. I recognize Poecilotriccus r. rufigenis provisionally pending the accumulation of new material. Geographical variation in size among populations of P. ruficeps is weakly clinal or chaotic. Crown and back colour are geographically uniform, however, and are identical among all populations of both P. ruficeps and P. luluae. In colour of belly and face, P. luluae is exceptionally stable and unique. This contrasts with striking geographical variation in facial colour and pattern in P. ruficeps. Although differences in song syllables are apparent, samples of tape recordings are too small to justify conclusions about the potential role of voice in reproductive isolation.