SYSTEMATICS OF THE TAWNY-BELLIED SEEDEATER (SPOROPHILA HYPOXANTHA). II. TAXONOMY AND EVOLUTIONARY IMPLICATIONS OF THE EXISTENCE OF A NEW TAWNY MORPH

ARETA JI; REPENNING M

THE CONDOR

COOPER ORNITHOLOGICAL SOC

Año: 2011 vol. 113 p. 678 - 690

0010-5422

The capuchinos, a subset of the genus Sporophila, represent a radiation of seedeaters characterized bylittle genetic differentiation, virtually no change in bill and body shape, marked plumage differences on a commontheme, and notable differentiation in vocalizations and habitat use. We describe a distinctive variant that would havebeen considered a species by the traditional strictly phenotypical criteria for classification of species in the genus. Thisvariant resembles the Tawny-bellied Seedeater (S. hypoxantha) but has a tawny, not gray, nape and back. It is also identicalin pattern to the Chestnut Seedeater (S. cinnamomea) but has a tawny rather than chestnut body. We tested fourhypotheses to assess the status of the variant: that it represents a new species, a hybrid S. hypoxantha × S. cinnamomea,a color morph of S. cinnamomea, or a color morph of S. hypoxantha. The variant is identical to S. hypoxantha in vocalizationsand habitat use, varying geographically in parallel. Both forms breed syntopically, and the tawny variant is recordedonly within the range of S. hypoxantha, with many records from areas where S. hypoxantha is the only breedingrepresentative of the ruficollis group. We consider the tawny variant to be a color morph of S. hypoxantha. Two nontrivialevolutionary paths can constitute precursors to speciation in the capuchinos: (1) differentiation in vocalizations andhabitat use arises with little plumage change in more or less geographically isolated populations, and (2) differentiationin plumage proceeds without change in vocalizations and habitat use within some populations.