Congruence between molecular and morphological data: species limits in the Pionus maximiliani (Kuhl, 1820) species complex

Pionus maximiliani, the Scaly-headed Parrot, is a widely distributed species in South America, ranging from northeastern Brazil to northern Argentina. It comprises four subspecies currently accepted: Pionus maximiliani maximiliani (Kuhl, 1820); P. m. siy, Souancé, 1856; P. m. melanoblepharus, Miranda-Ribeiro, 1920, and P. m. lacerus (Heine, 1884). Our purpose was assess species limits of P. maximiliani based on molecular and morphological characters. We overlayed plumage coloration and morphometric characters onto a multilocus dataset comprising two mitochondrial genes (ND2 and cytb) and two autosomal nuclear introns (TGFB2 and BF5). We inferred phylogenetic trees for each gene and concatenated dataset using Maximum Likelihood and Bayesian frameworks. We also evaluated geographic patterns through haplotype networks. Plumage data uncovered the existence of two distinct plumage patterns in which subspecies siy and lacerus exhibit the first one melanoblepharus and maximiliani shared the second one. Phylogenetic trees and haplotype networks indicate two well-supported clusters corresponding to the same grouping of the subspecies maximiliani + melanoblepharus and siy + lacerus. Hence, both plumage and molecular data support the existence of two well-supported lineages suggesting that they might deserve full species status according to the general lineage species concept. The two valid taxa would be Pionus maximiliani (Kuhl, 1820), which ranges the Atlantic Forest, from northeastern Brazil to northeastern Argentina, and Pionus siy Souancé, 1856, which is distributed in forested areas within Chaco, Pantanal and Yungas regions from Mato Grosso do Sul state in Brazil, to northwestern Argentina.