Historical diversification of floodplain forest specialist species in the Amazon: a case study with two species of the avian genus Xiphorhynchus (Aves: Dendrocolaptidae).

Abstract

Phylogeographical and population genetics methods are used to reconstruct the diversification history of two species of the genus Xiphorhynchus (Aves: Dendrocolaptidae) associated with seasonally flooded forest types in Amazonia. Sequences of the mitochondrial gene cytochrome b were assessed for 21 and 30 individuals, belonging to eight and ten populations, of Xiphorhynchus kienerii and Xiphorhynchus obsoletus , respectively. Uncorrected genetic distances among unique haplotypes recovered ranged only from 0.01% to 0.4% for both species. Over 90% of the genetic variation detected in both species was partitioned within populations, and therefore was not structured geographically. Mismatch distributions and values of Tajima’s D -tests indicate that both X. kienerii and X. obsoletus have had small evolutionary effective population sizes, but experienced a recent demographic expansion. These demographic expansions are tentatively dated as occurring over the last 18 000 years BP, a time frame which coincides with the establishment of the early and mid-Holocene age floodplain forest in most of central and eastern Amazonia, following a period of increased river stages throughout the basin. Based on phylogenetic, phylogeographical, and populations genetics data obtained for X. kienerii and X. obsoletus , an evolutionary scenario is proposed to account for the historical diversification of floodplain specialist species in Amazonia.