43
recent demographic histories of populations (e.g., chloroplast and mitochondrial
DNA polymorphisms), gave rise to phylogeographic studies. Then, different species
were studied, for example, several Nothofagus spp. (e.g., Marchelli et al. 1998;
Marchelli and Gallo 2006; Millerón et al. 2008; Azpilicueta et al. 2009; Acosta and
Premoli 2010; Mathiasen and Premoli 2010; Soliani et al. 2012; Acosta et al. 2014),
Embothrium coccineum (Vidal-Russell et al. 2011) and Araucaria araucana
(Marchelli et al. 2010). Most of these studies agreed in the persistence of the different species in multiple and scattered refugia. A joint analysis of animal and different
plant taxa suggested the existence of “lowland,” “peripheral,” and “valley” refugia,
located at six stable areas: east of the Patagonian Andes, northern Chiloé Island,
northern Chilean Coast, Atlantic Coastline, northern Patagonia, and South of Santa
Cruz Province and Tierra del Fuego (Sérsic et al. 2011). An interesting shared pattern is the inferred potential lowland refugia at high latitudes (Tierra del Fuego; 54°
S), both in the Andes and the Steppe (Jakob et al. 2009; Tremetsberger et al. 2009;
Cosacov et al. 2010; Mathiasen and Premoli 2010; Soliani et al. 2012). The ability
of populations to endure glacial times and persist in situ at these high latitudes
would have been facilitated by the particular glaciation setting of the Andes which
was notably different than the Northern Hemisphere (Markgraf et al. 1995), as
described in the first section of this chapter.
A general trend observed in many tree species of the Subantarctic forests is a latitudinal divergence of their genetic variation. Some phylogeographical breaks were
detected along the Patagonian Andes at 35° S, 37.5° S, 40.5° S, 43° S, and 50° S
(reviewed by Sérsic et al. 2011). For example two Nothofagus species (N. alpina
and N. obliqua) showed a genetic discontinuity at around 40° S (Marchelli et al.
1998; Azpilicueta et al. 2009) probably associated with the recent volcanic activity
of the Villarrica-Lanín volcanic chain (ca. 2700 years BP; Lara et al. 2004) that
might have avoided contact between northern and southern colonizing routes
(Millerón et al. 2008). The widely distributed N. pumilio and N. antarctica are characterized by a deep divergence in maternal lineages at around 43° S with two disjunct groups having different evolutionary histories (Mathiasen and Premoli 2010;
Soliani et al. 2012). Also among some conifers, latitudinal trends in the genetic
diversity were detected (e.g., A. chilensis, (Pastorino et al. 2004), A. araucana
(Bekessy et al. 2002)). It was proposed that the Andean breaks would be more
ancient (associated with Pre-Quaternary processes like Andean orogeny and paleobasins) than the stepparian breaks (related with Quaternary events like glaciations)
(Sérsic et al. 2011).
Another shared genetic pattern is the higher diversity at eastern and more isolated populations from the ecotone between the forests and the steppe. Eastern populations of, for example, Austrocedrus chilensis (Pastorino and Gallo 2002; Arana
et al. 2010), Fitzroya cupressoides (Premoli et al. 2000a), Nothofagus obliqua
(Azpilicueta et al. 2013; Soliani et al. 2020), and Araucaria araucana (Gallo et al.
2004; Marchelli et al. 2010) were found to be more genetically variable than larger
and continuous populations from western locations. Divergent gene pools in the
steppe together with high among population differentiation and high number of
2 Temperate Subantarctic Forests: A Huge Natural Laboratory
recent demographic histories of populations (e.g., chloroplast and mitochondrial
DNA polymorphisms), gave rise to phylogeographic studies. Then, different species
were studied, for example, several Nothofagus spp. (e.g., Marchelli et al. 1998;
Marchelli and Gallo 2006; Millerón et al. 2008; Azpilicueta et al. 2009; Acosta and
Premoli 2010; Mathiasen and Premoli 2010; Soliani et al. 2012; Acosta et al. 2014),
Embothrium coccineum (Vidal-Russell et al. 2011) and Araucaria araucana
(Marchelli et al. 2010). Most of these studies agreed in the persistence of the different species in multiple and scattered refugia. A joint analysis of animal and different
plant taxa suggested the existence of “lowland,” “peripheral,” and “valley” refugia,
located at six stable areas: east of the Patagonian Andes, northern Chiloé Island,
northern Chilean Coast, Atlantic Coastline, northern Patagonia, and South of Santa
Cruz Province and Tierra del Fuego (Sérsic et al. 2011). An interesting shared pattern is the inferred potential lowland refugia at high latitudes (Tierra del Fuego; 54°
S), both in the Andes and the Steppe (Jakob et al. 2009; Tremetsberger et al. 2009;
Cosacov et al. 2010; Mathiasen and Premoli 2010; Soliani et al. 2012). The ability
of populations to endure glacial times and persist in situ at these high latitudes
would have been facilitated by the particular glaciation setting of the Andes which
was notably different than the Northern Hemisphere (Markgraf et al. 1995), as
described in the first section of this chapter.
A general trend observed in many tree species of the Subantarctic forests is a latitudinal divergence of their genetic variation. Some phylogeographical breaks were
detected along the Patagonian Andes at 35° S, 37.5° S, 40.5° S, 43° S, and 50° S
(reviewed by Sérsic et al. 2011). For example two Nothofagus species (N. alpina
and N. obliqua) showed a genetic discontinuity at around 40° S (Marchelli et al.
1998; Azpilicueta et al. 2009) probably associated with the recent volcanic activity
of the Villarrica-Lanín volcanic chain (ca. 2700 years BP; Lara et al. 2004) that
might have avoided contact between northern and southern colonizing routes
(Millerón et al. 2008). The widely distributed N. pumilio and N. antarctica are characterized by a deep divergence in maternal lineages at around 43° S with two disjunct groups having different evolutionary histories (Mathiasen and Premoli 2010;
Soliani et al. 2012). Also among some conifers, latitudinal trends in the genetic
diversity were detected (e.g., A. chilensis, (Pastorino et al. 2004), A. araucana
(Bekessy et al. 2002)). It was proposed that the Andean breaks would be more
ancient (associated with Pre-Quaternary processes like Andean orogeny and paleobasins) than the stepparian breaks (related with Quaternary events like glaciations)
(Sérsic et al. 2011).
Another shared genetic pattern is the higher diversity at eastern and more isolated populations from the ecotone between the forests and the steppe. Eastern populations of, for example, Austrocedrus chilensis (Pastorino and Gallo 2002; Arana
et al. 2010), Fitzroya cupressoides (Premoli et al. 2000a), Nothofagus obliqua
(Azpilicueta et al. 2013; Soliani et al. 2020), and Araucaria araucana (Gallo et al.
2004; Marchelli et al. 2010) were found to be more genetically variable than larger
and continuous populations from western locations. Divergent gene pools in the
steppe together with high among population differentiation and high number of
2 Temperate Subantarctic Forests: A Huge Natural Laboratory