Final remarks
Our analyses of the evolutionary history of T. ruficapillus shows
that this species originated in the Late Pleistocene, within the last
1.7. million years, and diversified into three clearly differentiated
lineages: an Atlantic Forest lineage and two different lineages in the
Andes, with a split in western Bolivia. This pattern of genetic
variation highlights the relevance of the open vegetation corridor and
the Andes Mountains as diversification drivers for this species, likely
in combination with the effect of the Pleistocene climatic cycles.
Levels of phenotypic variation, however, are partially discordant with
this genetic structuring. Songs are significantly differentiated among
subspecies, but their geographic pattern of variation does not coincide
with that shown by mitochondrial or nuclear DNA. We found clearly
differentiated songs between subspecies that are genetically similar
and, on the contrary, lack of detectable song differentiation between
the Atlantic Forest subspecies and that of northwestern Bolivia in the
Andes, which present a substantial genetic differentiation and belong to
different lineages. Similarly, plumage colouration between the Atlantic
Forest subspecies and that of the southern Andes did not differ
significantly. Future studies should address these discordances with an
increased sampling and the analysis of the effect of evolutionary and
ecological pressures on song and colour. Finally, our results are in
accordance with those of other birds with disjunct populations in the
Atlantic and Andean forests for which the open vegetation corridor has
promoted diversification (e.g. Lavinia et al. 2015, 2019, Trujillo Arias
et al. 2018, 2020, Cabanne et al. 2019). However, these studies show
that the level of differentiation between the populations of these
forests is notoriously heterogeneous, suggesting an idiosyncratic effect
of this barrier and the cycles of connection and isolation of these
forests and highlighting the importance of comparative analyses to
better understand the role of the main drivers of avian Neotropical
diversification and speciation.