309
The Chaco and Espinal ecoregions of Argentina are under a strong use pressure
intending to convert these woodlands in agricultural crops (mainly soybean) or
extensive pasturelands. The subtropical dry forest of the humid Chaco walks its way
to agriculture, moving the traditional cattle production carried out there to the dry
Chaco and Espinal (and even to the Monte) ecoregions, which used to hold this
practice but at a lower intensity level. This sequence in rangeland use gives place to
a severe degradation risk. Anywhere grass forage tends to decrease or disappear;
cattle increases browsing pressure on shrubs and tree seedlings. In areas strongly
degraded by overstocking, instead of removing cattle, farmers usually prefer to
replace them by goats, which are capable of browsing on almost any type of available plant growth. This kind of decisions can determine disappearance of both the
wood characterizing the climax situation and the herbaceous cover in many locations (Fernández and Busso 1997). The situation is extremely fragile, and conservation and restoration practices need to be considered. Planting the key species of
these ecosystems must be planned taking into account the genetic factor.
The studies of A. caven populations showed that since differentiation in ecoregions was highly significant (Pometti et al. 2012), an adequate management strategy
for the use of this species in active restoration plans would be using local sources for
seed provision, namely, not moving seeds long distances, in order to prevent maladaptation and genetic contamination processes. Likewise, populations from the Puna
showed the highest level of structuration while those from the humid Chaco the
lowest. In this regard, the use of local seeds should be considered more rigorously
in the former.
In the case of A. visco, differentiation is lower than in A. caven, but still significant (Pometti et al. 2016), and the use of local seed sources is also recommendable
for restoration purposes. On the other side, the differentiation estimated among
A. aroma populations was the highest among these three acacias (42%), making it
essential to use local seed sources in case a restoration programme is conducted
with this species.
The findings of evidence of SGS and the estimation of gene dispersal (σ g ) for
A. aroma (Pometti et al. 2018) suggest that seed sampling for restoration programmes should consider a minimal distance between mother trees of 50 to 150 m
to minimize genetic relatedness among them. In cases of disturbed populations with
low density, the minimum and maximum distances should be much larger
(270/870 m). These results are important for managing and conserving the extant
trees and populations of the species in the fragmented landscapes (Pometti
et al. 2018).
Controlled crosses are currently being performed between trees with and without
spines in order to conduct genetic studies about the determinism of this trait in
A. aroma (Mauricio Ewens, personal communication). This research is conducted
in the frame of a collaboration between the Santiago del Estero Province –
Universidad Católica de Santiago del Estero agreement and the Universidad de
Buenos Aires.
There is scarce information about cultivation in the three species of Acacia studied here; however, there is some information about germination and dormancy of
11 Species Without Current Breeding Relevance But High Economic Value: Acaci
The Chaco and Espinal ecoregions of Argentina are under a strong use pressure
intending to convert these woodlands in agricultural crops (mainly soybean) or
extensive pasturelands. The subtropical dry forest of the humid Chaco walks its way
to agriculture, moving the traditional cattle production carried out there to the dry
Chaco and Espinal (and even to the Monte) ecoregions, which used to hold this
practice but at a lower intensity level. This sequence in rangeland use gives place to
a severe degradation risk. Anywhere grass forage tends to decrease or disappear;
cattle increases browsing pressure on shrubs and tree seedlings. In areas strongly
degraded by overstocking, instead of removing cattle, farmers usually prefer to
replace them by goats, which are capable of browsing on almost any type of available plant growth. This kind of decisions can determine disappearance of both the
wood characterizing the climax situation and the herbaceous cover in many locations (Fernández and Busso 1997). The situation is extremely fragile, and conservation and restoration practices need to be considered. Planting the key species of
these ecosystems must be planned taking into account the genetic factor.
The studies of A. caven populations showed that since differentiation in ecoregions was highly significant (Pometti et al. 2012), an adequate management strategy
for the use of this species in active restoration plans would be using local sources for
seed provision, namely, not moving seeds long distances, in order to prevent maladaptation and genetic contamination processes. Likewise, populations from the Puna
showed the highest level of structuration while those from the humid Chaco the
lowest. In this regard, the use of local seeds should be considered more rigorously
in the former.
In the case of A. visco, differentiation is lower than in A. caven, but still significant (Pometti et al. 2016), and the use of local seed sources is also recommendable
for restoration purposes. On the other side, the differentiation estimated among
A. aroma populations was the highest among these three acacias (42%), making it
essential to use local seed sources in case a restoration programme is conducted
with this species.
The findings of evidence of SGS and the estimation of gene dispersal (σ g ) for
A. aroma (Pometti et al. 2018) suggest that seed sampling for restoration programmes should consider a minimal distance between mother trees of 50 to 150 m
to minimize genetic relatedness among them. In cases of disturbed populations with
low density, the minimum and maximum distances should be much larger
(270/870 m). These results are important for managing and conserving the extant
trees and populations of the species in the fragmented landscapes (Pometti
et al. 2018).
Controlled crosses are currently being performed between trees with and without
spines in order to conduct genetic studies about the determinism of this trait in
A. aroma (Mauricio Ewens, personal communication). This research is conducted
in the frame of a collaboration between the Santiago del Estero Province –
Universidad Católica de Santiago del Estero agreement and the Universidad de
Buenos Aires.
There is scarce information about cultivation in the three species of Acacia studied here; however, there is some information about germination and dormancy of
11 Species Without Current Breeding Relevance But High Economic Value: Acaci