Choosing between Cerrado and Chaco: Which corridor connected the Andean and Atlantic forest populations of the Buff-browed Foliage Gleaner?

Genetic study provides several lines of evidence for a Cerrado connection.

The Buff-browed Foliage Gleaner (Syndactyla rufosuperciliata) is a small passerine that occurs in the tropical forests of South America. You can find it in the west (Andean forests) and in the east (Atlantic forests) of this continent. In the center, however, this species is absent: the dry and open vegetation functions as a barrier between the Andean and Atlantic forests (the so-called Open Vegetation Corridor). This distribution suggest that eastern and western populations of the Buff-browed Foliage Gleaner were connected at some point in time.

There are two possible connections between the Andean and Atlantic forests: the Chaco in the south and the Cerrado in the north (see map below). Several botanical studies indicated that these regions were forested during the Pleistocene, allowing birds to travel between the Andean and Atlantic forests. But which route did the Buff-browed Foliage Gleaner use? A recent study in the journal Molecular Phylogenetics and Evolution provides evidence for a Cerrado connection.

Syndactyla_rufosuperciliata

A Buff-browed Foliage Gleaner in Brazil © Cláudio Dias Timm | Wikimedia Commons

 

Evidence for the Cerrado Connection

Gustavo Cabanne and his colleagues collected DNA-samples for all known subspecies of the Buff-browed Foliage Gleaner. A suite of genetic analyses all pointed to a Cerrado connection. Here is the brief summary:

  1.  Isolation-with-Migration analyses uncovered a clear split between the Andean and Atlantic populations that occurred during the Pleistocene. Moreover, there were high levels of gene flow between the populations in northern Bolivia and the Atlantic forest population.
  2. A cluster analysis (based on the mitochondrial gene cytb) grouped the northern Andean individuals (from Peru) with the North Atlantic population.
  3. Demographic modelling rejected the Chaco-corridor model and supported a Cerrado connection.
Buff-browed Foliage Gleaner

The Buff-browed Foliage Gleaner occurs in the Andean and Atlantic forests. These populations have been connected in the past through the Cerrado corridor (arrow I in figure A). There was less evidence for a Chaco connectoin (arrow II in figure A).  From: Cabanne et al. (2019) Molecular Phylogenetics and Evolution

 

Taxonomic Issues

As mentioned above, the researchers found a clear split between the Andean and Atlantic populations. They suggest to treat these populations as distinct species. The Andean species would be comprised of three subspecies (oleaginea, cabanisi and similis) while the Atlantic species holds two subspecies (acrita and rufosuperciliata).

Interestingly (especially for this website), the analyses also revealed gene flow between the Buff-browed Foliage-gleaner and its sister species, the Russet-mantled Foliage-gleaner (Syndactyla dimidiata). These species overlap – and apparently interbreed – in Paraguay and Brazil. Another hybrid zone to study!

Syndactyla dimidiata

The Russet-mantled Foliage-gleaner is hybridizing with the Buff-browed Foliage-gleaner © Hector Bottai | Wikimedia Commons

 

References

Cabanne et al. (2019) Phylogeographic variation within the Buff-browed Foliage-gleaner (Aves: Furnariidae: Syndactyla rufosuperciliata) supports an Andean-Atlantic forests connection via the Cerrado. Molecular Phylogenetics and Evolution133: 198-213.

 

This paper has been added to the Furnariidae page.

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