Genetic and phenotypic differentiation in a Neotropical passerine with a
disjunct distribution in the Andean and Atlantic forests (Thamnophilus
ruficapillus)
Abstract
The Andean and Atlantic forests are separated by the open vegetation
corridor, which acts as a geographic barrier. However, these forests
experimented cycles of connection and isolation in the past which shaped
the phylogeographic patterns of their biotas. We analyzed the
evolutionary history of the Rufous-capped Antshrike (Thamnophilus
ruficapillus), a species with a disjunct distribution in the Atlantic
and Andean forests and therefore an appropriate model to study the
effect of the open vegetation corridor and the Andes on the
diversification of the Neotropical avifauna. We performed a
phylogenetic/phylogeographic analysis including the five subspecies,
using mitochondrial and nuclear genomic DNA, and also studied their
differences in vocalizations and plumage coloration. Both the
mitochondrial and nuclear DNA evidenced a marked phylogeographic
structure with three differentiated lineages that diverged without gene
flow in the Pleistocene (1.0-1.7 million years ago): one in the Atlantic
Forest and two in the Andean forest. However, the two Andean lineages do
not coincide with the two disjunct areas of distribution of the species
in the Andes. Vocalizations were significantly different between most
subspecies, but their pattern of differentiation was discordant with
that of the nuclear and mitochondrial DNA. In fact, there is no song
differentiation between the subspecies of the Atlantic Forest and that
of the northwestern Bolivian Andes, even though they differ genetically
and belong to different lineages. Consistently, no differences were
found in plumage coloration between the subspecies of the Atlantic
Forest and that of the southern Andes. Our results suggest a complex
evolutionary history in this species, which differentiated both due to
dispersion across the open vegetation corridor, likely during a period
of connection between the Andean and Atlantic forests, and as a
consequence of a geographic barrier in northern Bolivia. In both cases
Pleistocene climatic oscillations appear to have influenced the species
diversification.