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.
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