Análise da variação fenotípica e genotípica do complexo Brotogeris sanctithomae (Aves: Psittaciformes)

Abstract

Brotogeris sanctithomae is a parakeet of the Amazonian floodplain forests, recognized by its yellow forehead contrasting with its otherwise all-green plumage. Its two subspecies are distinguished by a yellow mark in the post-ocular region present in B. s. takatsukasae, of eastern Amazonia, and absent in B. s. sanctithomae, from the western portion. The two meet somewhere near Manaus, although their geographical limits are not clear in the literature. Despite the phenotypic differences and distinct distributions, a recent phylogenetic analysis of Brotogeris did not find molecular covariance (ND2, cytochrome b intron 7 of beta-fibrinogen gene) that distinguishes the two taxa. We set out to understand the evolutionary processes related to the pattern of plumage differentiation between the two subspecies, and to determine the geographic distribution of phenotypic and genotypic variation. We sampled throughout the stretch of floodplains where the two subspecies replace one another (between Manacapuru and Parintins, Amazonas). We conducted a morphological analysis of these individuals and specimens in ornithological collections and developed SNP (Single Nucleotide Polymorphism) markers from ddRAD tags (double digested Restriction-site Associated DNA). Two genetic groups were found, corresponding with the phenotypic groups (subspecies). The two subspecies share most of the genome, diverging only in a few loci. These divergent loci were more strongly associated with iris color than presence/absence of the post-ocular mark. This character may maintain differentiation between the two subspecies via sexual selection, whereby morphologically distinct individuals tend not to pair. Hybridization occurs in a restricted region between the distributions of the pure phenotypes. Recognition of hybrids in a narrow region without geographic barriers, rather than gradual phenotypic and genotypic variation on a long cline, suggests secondary contact between populations previously differentiated in allopatry.