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11.2 Genetic Diversity by Means of Molecular Markers
Genetic diversity is the result of long-term evolution and represents the evolutionary
potential of a species. Surviving in a varying environment requires the accumulation
of genetic variation in order to increase adaptability (Li et al. 1999). Accurate estimates of genetic diversity are useful for optimizing sampling strategies and for conserving and managing the genetic diversity of trees (Hamrick and Godt 1996).
Six botanical varieties were described for A. caven (var. caven, var. dehiscens,
var. sphaerocarpa, var. stenocarpa, var. microcarpa and var. macrocarpa) based on
both morphological traits (Aronson 1992; Pometti et al. 2007) and RAPD markers
(Pometti et al. 2010). Argentina is the only country where all six varieties are present (Aronson 1992).
The genetic diversity of the species was studied for 15 Argentinian populations
belonging to the six mentioned varieties by means of RAPD and AFLP techniques.
With RAPD, genetic diversity (expected heterozygosity: H E ) ranged from 0.16 to
0.33 (mean H E = 0.254) and percentage of polymorphic loci PPL varied from 27.7%
to 97.9% (mean PPL = 78.73%), evaluating 47 discernible bands (Pometti et al.
2010). In the case of AFLP technique, 217 neutral loci were evaluated, and PPL
ranged from 65% to 93.5% (mean PPL = 78.2%), meanwhile H E ranged from 0.206
to 0.353 (mean H E = 0.278) (Pometti et al. 2012).
In the case of A. aroma, six Argentine populations were studied where H E varied
from 0.18 to 0.24 (mean H E = 0.21), and PPL varied from 56.4% to 67.1% (mean
PPL = 62.1%). These values were obtained with 401 AFLP loci (Pometti et al. 2018).
In A. visco, PPL ranged from 43.4% to 74.2% with a mean of 60.89% over the
seven Argentine populations analysed. Estimations of H E varied from 0.16 to 0.26
with a mean of 0.20. These indices were obtained by means of 431 AFLP loci
(Pometti et al. 2016). The estimates of genetic diversity for the three species of
Acacia mentioned here were similar to other widely distributed African and
American acacias like A. albida, A. senegal, A. raddiana, A. farnesiana and A. curvifructa (Shrestha et al. 2002; Chiveu et al. 2008; Pometti et al. 2015).
A total of 132 individuals of P. affinis distributed in 16 fragments of native forest
within an agricultural intensification gradient in the West-Centre of the Province of
Entre Ríos (Central-Eastern Argentina) were examined. They were assessed by
means of the patterns obtained for ten polymorphic SSR markers transferred from
phylogenetically close species (Soldati et al. 2018). Descriptive parameters of
genetic diversity were estimated. Unbiased expected heterozygosity levels were
moderate (from 0.621 to 0.816), with an average value of U H E = 0.734. Numerous
exclusive alleles (Ea) were found, distributed within the fragments of native forest,
in a range of 0 to 4. Nei’s genetic distance among fragments was low to moderate,
with an average value of 0.238. Higher levels of genetic variability were found in
the forest fragments sampled in areas of the gradient with greater agricultural
expansion.
The knowledge about P. caldenia genetic diversity and mating system is scarce,
and specific studies using DNA markers such as RAPD, ISSR or SSR are restricted
C. Pometti et al.
11.2 Genetic Diversity by Means of Molecular Markers
Genetic diversity is the result of long-term evolution and represents the evolutionary
potential of a species. Surviving in a varying environment requires the accumulation
of genetic variation in order to increase adaptability (Li et al. 1999). Accurate estimates of genetic diversity are useful for optimizing sampling strategies and for conserving and managing the genetic diversity of trees (Hamrick and Godt 1996).
Six botanical varieties were described for A. caven (var. caven, var. dehiscens,
var. sphaerocarpa, var. stenocarpa, var. microcarpa and var. macrocarpa) based on
both morphological traits (Aronson 1992; Pometti et al. 2007) and RAPD markers
(Pometti et al. 2010). Argentina is the only country where all six varieties are present (Aronson 1992).
The genetic diversity of the species was studied for 15 Argentinian populations
belonging to the six mentioned varieties by means of RAPD and AFLP techniques.
With RAPD, genetic diversity (expected heterozygosity: H E ) ranged from 0.16 to
0.33 (mean H E = 0.254) and percentage of polymorphic loci PPL varied from 27.7%
to 97.9% (mean PPL = 78.73%), evaluating 47 discernible bands (Pometti et al.
2010). In the case of AFLP technique, 217 neutral loci were evaluated, and PPL
ranged from 65% to 93.5% (mean PPL = 78.2%), meanwhile H E ranged from 0.206
to 0.353 (mean H E = 0.278) (Pometti et al. 2012).
In the case of A. aroma, six Argentine populations were studied where H E varied
from 0.18 to 0.24 (mean H E = 0.21), and PPL varied from 56.4% to 67.1% (mean
PPL = 62.1%). These values were obtained with 401 AFLP loci (Pometti et al. 2018).
In A. visco, PPL ranged from 43.4% to 74.2% with a mean of 60.89% over the
seven Argentine populations analysed. Estimations of H E varied from 0.16 to 0.26
with a mean of 0.20. These indices were obtained by means of 431 AFLP loci
(Pometti et al. 2016). The estimates of genetic diversity for the three species of
Acacia mentioned here were similar to other widely distributed African and
American acacias like A. albida, A. senegal, A. raddiana, A. farnesiana and A. curvifructa (Shrestha et al. 2002; Chiveu et al. 2008; Pometti et al. 2015).
A total of 132 individuals of P. affinis distributed in 16 fragments of native forest
within an agricultural intensification gradient in the West-Centre of the Province of
Entre Ríos (Central-Eastern Argentina) were examined. They were assessed by
means of the patterns obtained for ten polymorphic SSR markers transferred from
phylogenetically close species (Soldati et al. 2018). Descriptive parameters of
genetic diversity were estimated. Unbiased expected heterozygosity levels were
moderate (from 0.621 to 0.816), with an average value of U H E = 0.734. Numerous
exclusive alleles (Ea) were found, distributed within the fragments of native forest,
in a range of 0 to 4. Nei’s genetic distance among fragments was low to moderate,
with an average value of 0.238. Higher levels of genetic variability were found in
the forest fragments sampled in areas of the gradient with greater agricultural
expansion.
The knowledge about P. caldenia genetic diversity and mating system is scarce,
and specific studies using DNA markers such as RAPD, ISSR or SSR are restricted
C. Pometti et al.