93
Cordillera during postglacial recolonisation. Hybridisation and introgression processes with taxa such as N. macrocarpa and N. leonii from Chilean populations
could not be discarded according to this hypothesis (Azpilicueta et al. 2016b).
Further studies are necessary to detect highly divergent molecular markers among
these taxa and finally achieve a higher degree of accuracy in the taxonomic identification of robles from Epulauquen population.
Although N. obliqua populations grow mostly within a precipitation range of
1200–2500 mm/year in Argentina, the easternmost population, Pilo lil, is located in
more xeric conditions, with a precipitation regime of ca. 700 mm/year (Fig. 4.2).
Here, the species conforms mixed forests with the native conifer Austrocedrus
chilensis. Although ecophysiological behaviour of Pilo lil seedlings subject to
drought stress experiments could not be differentiated from that of more humid
populations (Varela et al. 2010), adaptation processes might be expected at this
extreme and xeric environment.
More than 90% of roble pellín forests in Argentina stand in protected areas
(Sabatier et al. 2011). However, historical over-exploitation and the restricted area
that this species occupy in Argentina highlight the need of a deeply discussion about
their present and future conservation and management.
4.1.2 Hybridisation Processes
Natural hybridisation is common between species of the Nothofagus genus.
Nothofagus × leonii Espinosa (Donoso and Landrum 1979; Grant and Clement
2004) is recognised as the hybrid between N. obliqua and N. glauca. Also, hybridisation between N. obliqua and N. macrocarpa has been suggested (Vázquez and
Rodríguez 1999). Likewise, natural hybridisation between N. obliqua and N. alpina
has been reported, firstly based on morphological traits (Donoso et al. 1990) and
later confirmed by genetic studies (Gallo et al. 1997), emphasising the evolutionary
importance of this genetic process for the long-term maintenance of intra-generic
variation. Even more, Vergara et al. (2014) postulated the hybridisation of N. obliqua with both N. alpina and N. glauca in northern Chilean populations in order to
explain the admixture found while analysing molecular data of these three sympatric species.
In Argentina, N. obliqua hybridises with N. alpina (Donoso et al. 1990; Gallo
et al. 1997; Marchelli and Gallo 2001; Gallo 2004) in sympatric areas such as the
basins of the lakes Lácar and Quillén. Gallo (2002) proposed a conceptual model of
introgressive hybridisation for these species, which is characterized by hybridisation asymmetry (N. obliqua acting as pollen donor) and bidirectionality of introgression and low fitness of F1 hybrids at low temperatures. The latter feature is
based on the results of a progeny trial including both pure and hybrid juvenile individuals, where 15% of the hybrids exhibited higher performance in growth characters but showed a high rate of mortality (~ 40%), probably related to susceptibility
to low temperatures (Crego 1999; Gallo 2004). Gallo (2002) also highlighted the
4 Roble pellín (Nothofagus obliqua): A Southern Beech with a Restricted…
Cordillera during postglacial recolonisation. Hybridisation and introgression processes with taxa such as N. macrocarpa and N. leonii from Chilean populations
could not be discarded according to this hypothesis (Azpilicueta et al. 2016b).
Further studies are necessary to detect highly divergent molecular markers among
these taxa and finally achieve a higher degree of accuracy in the taxonomic identification of robles from Epulauquen population.
Although N. obliqua populations grow mostly within a precipitation range of
1200–2500 mm/year in Argentina, the easternmost population, Pilo lil, is located in
more xeric conditions, with a precipitation regime of ca. 700 mm/year (Fig. 4.2).
Here, the species conforms mixed forests with the native conifer Austrocedrus
chilensis. Although ecophysiological behaviour of Pilo lil seedlings subject to
drought stress experiments could not be differentiated from that of more humid
populations (Varela et al. 2010), adaptation processes might be expected at this
extreme and xeric environment.
More than 90% of roble pellín forests in Argentina stand in protected areas
(Sabatier et al. 2011). However, historical over-exploitation and the restricted area
that this species occupy in Argentina highlight the need of a deeply discussion about
their present and future conservation and management.
4.1.2 Hybridisation Processes
Natural hybridisation is common between species of the Nothofagus genus.
Nothofagus × leonii Espinosa (Donoso and Landrum 1979; Grant and Clement
2004) is recognised as the hybrid between N. obliqua and N. glauca. Also, hybridisation between N. obliqua and N. macrocarpa has been suggested (Vázquez and
Rodríguez 1999). Likewise, natural hybridisation between N. obliqua and N. alpina
has been reported, firstly based on morphological traits (Donoso et al. 1990) and
later confirmed by genetic studies (Gallo et al. 1997), emphasising the evolutionary
importance of this genetic process for the long-term maintenance of intra-generic
variation. Even more, Vergara et al. (2014) postulated the hybridisation of N. obliqua with both N. alpina and N. glauca in northern Chilean populations in order to
explain the admixture found while analysing molecular data of these three sympatric species.
In Argentina, N. obliqua hybridises with N. alpina (Donoso et al. 1990; Gallo
et al. 1997; Marchelli and Gallo 2001; Gallo 2004) in sympatric areas such as the
basins of the lakes Lácar and Quillén. Gallo (2002) proposed a conceptual model of
introgressive hybridisation for these species, which is characterized by hybridisation asymmetry (N. obliqua acting as pollen donor) and bidirectionality of introgression and low fitness of F1 hybrids at low temperatures. The latter feature is
based on the results of a progeny trial including both pure and hybrid juvenile individuals, where 15% of the hybrids exhibited higher performance in growth characters but showed a high rate of mortality (~ 40%), probably related to susceptibility
to low temperatures (Crego 1999; Gallo 2004). Gallo (2002) also highlighted the
4 Roble pellín (Nothofagus obliqua): A Southern Beech with a Restricted…