Geographic variation and species limits in Cinnycerthia wrens of the Andes
Abstract
Few studies have quantified geographic variation in widely distributed Andean birds despite the lace that the linearity of their distributions provides unique opportunity to assess latitudinal geographic variation. We examined geographic variation of morphometric and plumage characters in populations currently treated as a single species, the Sepia-brown Wren (Cinnycerthia peruana), that inhabits humid montane forests from northern Colombia to central Bolivia. Our analysis supports the recognition of three biological species (olivascens, peruana, and fulva) based on discrete morphometric differences as well as marked plumage differences. Size variation within populations is inconsistent with the predictions of Bergmann's Rule, whereas variation across species runs counter to the predictions, with the smallest species occurring farthest from the Equator.