Multilocus tests of Pleistocene refugia and ancient divergence in a pair of Atlantic Forest antbirds (Myrmeciza)


do Amaral FR, Albers PK, Edwards SV, Miyaki CY. Multilocus tests of Pleistocene refugia and ancient divergence in a pair of Atlantic Forest antbirds (Myrmeciza). Molecular Ecology [Internet]. 2013;22 (15) :3996-4013.
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The Atlantic Forest (AF) harbours one of the most diverse vertebrate faunas of the
world, including 199 endemic species of birds. Understanding the evolutionary pro-
cesses behind such diversity has become the focus of many recent, primarily single
locus, phylogeographic studies. These studies suggest that isolation in forest refugia
may have been a major mechanism promoting diversification, although there is also
support for a role of riverine and geotectonic barriers, two sets of hypotheses that can
best be tested with multilocus data. Here we combined multilocus data (one mtDNA
marker and eight anonymous nuclear loci) from two species of parapatric antbirds,
Myrmeciza loricata
M. squamosa
, and Approximate Bayesian Computation to
determine whether isolation in refugia explains current patterns of genetic variation
and their status as independent evolutionary units. Patterns of population structure,
differences in intraspecific levels of divergence and coalescent estimates of historical
demography fit the predictions of a recently proposed model of refuge isolation in
which climatic stability in the northern AF sustains higher diversity and demographic
stability than in the southern AF. However, a pre-Pleistocene divergence associated
with their abutting range limits in a region of past tectonic activity also suggests a role
for rivers or geotectonic barriers. Little or no gene flow between these species suggests
the development of reproductive barriers or competitive exclusion. Our results sug-
gests that limited marker sampling in recent AF studies may compromise estimates of
divergence times and historical demography, and we discuss the effects of such sam-
pling on this and other studies.

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