Speciation in the Carbonated Flower-Piercer (Diglossa carbonaria) Complex of the Andes

Abstract

The evolution, differentiation and present distribution of the carbonated flower-piercer (D. carbonaria) superspecies were apparently greatly affected by Pleistocene glacial cycles. Populations of the 6 principal morphotypes are now largely allopatric, although secondary contact occurs in northern Peru (D. humeralis aterrima and D. brunneiventris brunneiventris) and northwestern Bolivia (D. b. brunneiventris and D. carbonaria). A narrow zone of hybridization between D. b. brunneiventris and D. carbonaria occurs northeast of La Paz, Bolivia. The presence of hybrid-like individuals in allopatric populations from eastern Bolivia D. (carbonaria), Colombia (D. humeralis) and Venezuela (D. gloriosa) may be due to past genetic contact and not to present introgression from nearby forms. The forms D. h. aterrima, D. h. humeralis and D. h. nocticolor are closely related and conspecific (D. humeralis). The form D. h. gloriosa is a distinct allospecies. The Colombian population of D. b. brunneiventris is subspecifically distinct from the nominate form. The forms D. b. brunneiventris and D. carbonaria are closely related, but assuming the existence of a partial isolating mechanism between them, should be recognized as allospecies (D. brunneiventris and D. carbonaria). A model of speciation that accounts for the disjunction of similar phenotypes is presented. Differentiation in isolation occurred in a number of high Andean forest refuges during Pleistocene glacials and interglacials, and dispersal and genetic contact occurred with altitudinal changes in timberline forest at the beginnings and terminations of glacial periods.