Systematics of the Tawny-Bellied Seedeater (Sporophila hypoxantha). II. Taxonomy and Evolutionary Implications of the Existence of a New Tawny Morph

Abstract. The capuchinos, a subset of the genus Sporophila, represent a radiation of seedeaters characterized by little genetic differentiation, virtually no change in bill and body shape, marked plumage differences on a common theme, and notable differentiation in vocalizations and habitat use. We describe a distinctive variant that would have been considered a species by the traditional strictly phenotypical criteria for classification of species in the genus. This variant resembles the Tawny-bellied Seedeater (S. hypoxantha) but has a tawny, not gray, nape and back. It is also identical in pattern to the Chestnut Seedeater (S. cinnamomea) but has a tawny rather than chestnut body. We tested four hypotheses 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 vocalizations and habitat use, varying geographically in parallel. Both forms ...