95
present distribution patterns and the genetic structure of southern South American
temperate forests (Veit and Garleff 1996), by their retraction and posterior expansion from glacial refuges, colonisation routes and convergence points.
To evaluate the impact of these changes on the genetic structure of N. obliqua
populations, a phylogeographical analysis based on chloroplast DNA was carried
out including the whole range of this species (Azpilicueta et al. 2009). Three intergenic chloroplast DNA regions were analysed on 27 natural populations of Chile
and Argentina. Evidence of glacial refuges in the Chilean Coastal Range were
shown (this region harbours high diversity together with old and private haplotypes), which is in agreement with previous studies based on pollen records
(Villagrán 1991, 2001). Notwithstanding, refuges were also inferred along the
Andes Cordillera and the Longitudinal Valley thus revealing a survival pattern of
multiple glacial refuges during the Last Glacial Maximum, ca. 18,000–20,000 years
BP. Therefore, and considering only the restricted Argentinean range of N. obliqua,
two maternal lineages were identified (north and south of Lanín volcano at ~39°40′
S) which seems to be the latitudinal limit, inferring at least two different glacial
origins.
In a subsequent study (Azpilicueta and Gallo 2009), 14 Argentinean natural populations were subjected to genetic analysis using isozymes. The genetic pattern found
suggested distinct glacial origins for northern and southern populations, as shown
with cpDNA markers. Evenmore, and based on allelic richness, relict areas could be
postulated within each of the identified latitudinal groups. An additional study based
on the analysis of seven nuclear microsatellite markers was carried out in ten
Argentinean N. obliqua populations (Azpilicueta et al. 2013). Higher mutation rates
of microsatellites in comparison with isozymes allowed higher sensitivity to polymorphism detection. Once again, higher allelic richness values were found in the surroundings of areas identified as potential glacial refuges, what suggests that the
distribution pattern of allelic richness is closely associated with the history of N. obliqua in this region during the glaciations. Likewise, along the Chilean distribution
area, Vergara et al. (2014) analysed 20 populations of this species with 7 microsatellites. Three latitudinal regions were detected (at north and south of 36° S and south of
38°30′ S, respectively), allowing the reconstruction of the area affected by the most
recent ice age based on the genetic structure of N. obliqua and suggesting several
centres of genetic diversity in agreement with the multiple refugia hypothesis.
The combined analysis of cpDNA intergenic regions, isozymes and microsatellites allowed the recognition of potential refuges east of the Andes Cordillera at
Epulauquen and the likely convergence points of postglacial migratory routes.
Rucañancu (39°33′ S) is postulated as a potential refuge at the Longitudinal Valley
in Chile with a migratory route coming from the north also confluencing in this area.
In Argentina, Epulauquen forests could have probably conformed an Eastern refuge, with the arrival of a Western introgression after ice-retraction (Azpilicueta and
Gallo 2009; Azpilicueta et al. 2009, 2013). Biochemical and molecular neutral
markers proved to be valuable tools for the study of past demographic changes and
distribution levels of genetic variation in order to retrace the evolutionary history of
N. obliqua forests, allowing their historical reconstruction (Azpilicueta and Gallo
2009; Azpilicueta et al. 2009, 2013; Vergara et al. 2014).
4 Roble pellín (Nothofagus obliqua): A Southern Beech with a Restricted…
present distribution patterns and the genetic structure of southern South American
temperate forests (Veit and Garleff 1996), by their retraction and posterior expansion from glacial refuges, colonisation routes and convergence points.
To evaluate the impact of these changes on the genetic structure of N. obliqua
populations, a phylogeographical analysis based on chloroplast DNA was carried
out including the whole range of this species (Azpilicueta et al. 2009). Three intergenic chloroplast DNA regions were analysed on 27 natural populations of Chile
and Argentina. Evidence of glacial refuges in the Chilean Coastal Range were
shown (this region harbours high diversity together with old and private haplotypes), which is in agreement with previous studies based on pollen records
(Villagrán 1991, 2001). Notwithstanding, refuges were also inferred along the
Andes Cordillera and the Longitudinal Valley thus revealing a survival pattern of
multiple glacial refuges during the Last Glacial Maximum, ca. 18,000–20,000 years
BP. Therefore, and considering only the restricted Argentinean range of N. obliqua,
two maternal lineages were identified (north and south of Lanín volcano at ~39°40′
S) which seems to be the latitudinal limit, inferring at least two different glacial
origins.
In a subsequent study (Azpilicueta and Gallo 2009), 14 Argentinean natural populations were subjected to genetic analysis using isozymes. The genetic pattern found
suggested distinct glacial origins for northern and southern populations, as shown
with cpDNA markers. Evenmore, and based on allelic richness, relict areas could be
postulated within each of the identified latitudinal groups. An additional study based
on the analysis of seven nuclear microsatellite markers was carried out in ten
Argentinean N. obliqua populations (Azpilicueta et al. 2013). Higher mutation rates
of microsatellites in comparison with isozymes allowed higher sensitivity to polymorphism detection. Once again, higher allelic richness values were found in the surroundings of areas identified as potential glacial refuges, what suggests that the
distribution pattern of allelic richness is closely associated with the history of N. obliqua in this region during the glaciations. Likewise, along the Chilean distribution
area, Vergara et al. (2014) analysed 20 populations of this species with 7 microsatellites. Three latitudinal regions were detected (at north and south of 36° S and south of
38°30′ S, respectively), allowing the reconstruction of the area affected by the most
recent ice age based on the genetic structure of N. obliqua and suggesting several
centres of genetic diversity in agreement with the multiple refugia hypothesis.
The combined analysis of cpDNA intergenic regions, isozymes and microsatellites allowed the recognition of potential refuges east of the Andes Cordillera at
Epulauquen and the likely convergence points of postglacial migratory routes.
Rucañancu (39°33′ S) is postulated as a potential refuge at the Longitudinal Valley
in Chile with a migratory route coming from the north also confluencing in this area.
In Argentina, Epulauquen forests could have probably conformed an Eastern refuge, with the arrival of a Western introgression after ice-retraction (Azpilicueta and
Gallo 2009; Azpilicueta et al. 2009, 2013). Biochemical and molecular neutral
markers proved to be valuable tools for the study of past demographic changes and
distribution levels of genetic variation in order to retrace the evolutionary history of
N. obliqua forests, allowing their historical reconstruction (Azpilicueta and Gallo
2009; Azpilicueta et al. 2009, 2013; Vergara et al. 2014).
4 Roble pellín (Nothofagus obliqua): A Southern Beech with a Restricted…