438
prioritized in domestication, breeding, and conservation programs of the species. In
general, no inbreeding was detected, with almost all populations with F IS near to 0.
In order to examine genetic differentiation among populations (Phi PT ), a hierarchical analysis of molecular variance (AMOVA, Excoffier et al. 1992) was performed by means of GenAlEx 6.2. A moderate to low genetic differentiation among
populations was observed, and this was highly significant (Phi PT = 0.049, p ≤ 0.001).
As it is generally expected for forest species, most of the genetic variation was
observed within populations (95%), and this is consistent with the high level of
observed historical gene flow, Nm = 4.85. To assess more in detail the population
genetic structure, a Bayesian clustering approach by Structure 2.3.4 (Pritchard et al.
2000; Evanno et al. 2005; Falush et al. 2007) and Nei’s genetic distances among
populations and genetic similarities among individuals by NTSYS 2.0 (Nei 1978;
Rohlf 1998) were performed (Inza et al. 2019).
Six genetic clusters were identified (K = 6), and they were generally distributed
homogeneously between populations, meaning a weak genetic structure (Fig. 16.4).
Clusters 1 (red), 2 (green), 3 (blue), 4 (yellow), and 6 (light blue) are present in
proportions of 16–21% in all populations. However, for cluster 5 (pink), populations showed some differences with maximum values for Burruyacú and Río Seco
(18 and 15%, respectively), which is principally due to the presence of this cluster
in some trees. In Río Seco, trees 11 and 670 showed the highest proportion of this
cluster which is consistent with the higher number of Ea and the greater genetic
distance of these genotypes to the others. Cluster 5 showed a minimum proportion
for El Talar (5%) and the three populations of southern Yungas (3%, San Pablo,
Lules, and Huasapampa) that were very similar in their genetic composition. These
results are consistent with the genetic distance among populations from the UPGMA
dendrogram (r = 0.84, data not shown). The genetic similarity between some trees
stresses the need to continue the study with a higher number of molecular markers
that allows an unequivocal identification of all trees.
This is a preliminary study as a basis of knowledge of the genetic variability
pattern of H. impetiginosus in the Argentine Yungas Rainforest to guide domestication, breeding, and conservation purposes. As general conclusions, Río Seco, Pocoy,
and Burruyacú populations should be prioritized according to their higher genetic
diversity and differentiation levels, and conservation measures (including ex situ
strategies) should be implemented. San Pablo and Rosario de la Frontera populations have an important value due to their genetic diversity levels despite its low
number of sampled trees. Some populations have an additional value because of
their important geographical position. Rosario de la Frontera connects NorthCentral with Southern Yungas, and Huasapampa and Lules are on the southern edge
of natural range of the species, and they could have an adaptive value. Future studies
increasing both sample size and number of markers are needed for more conclusive
results.
L. F. Fornes et al.
prioritized in domestication, breeding, and conservation programs of the species. In
general, no inbreeding was detected, with almost all populations with F IS near to 0.
In order to examine genetic differentiation among populations (Phi PT ), a hierarchical analysis of molecular variance (AMOVA, Excoffier et al. 1992) was performed by means of GenAlEx 6.2. A moderate to low genetic differentiation among
populations was observed, and this was highly significant (Phi PT = 0.049, p ≤ 0.001).
As it is generally expected for forest species, most of the genetic variation was
observed within populations (95%), and this is consistent with the high level of
observed historical gene flow, Nm = 4.85. To assess more in detail the population
genetic structure, a Bayesian clustering approach by Structure 2.3.4 (Pritchard et al.
2000; Evanno et al. 2005; Falush et al. 2007) and Nei’s genetic distances among
populations and genetic similarities among individuals by NTSYS 2.0 (Nei 1978;
Rohlf 1998) were performed (Inza et al. 2019).
Six genetic clusters were identified (K = 6), and they were generally distributed
homogeneously between populations, meaning a weak genetic structure (Fig. 16.4).
Clusters 1 (red), 2 (green), 3 (blue), 4 (yellow), and 6 (light blue) are present in
proportions of 16–21% in all populations. However, for cluster 5 (pink), populations showed some differences with maximum values for Burruyacú and Río Seco
(18 and 15%, respectively), which is principally due to the presence of this cluster
in some trees. In Río Seco, trees 11 and 670 showed the highest proportion of this
cluster which is consistent with the higher number of Ea and the greater genetic
distance of these genotypes to the others. Cluster 5 showed a minimum proportion
for El Talar (5%) and the three populations of southern Yungas (3%, San Pablo,
Lules, and Huasapampa) that were very similar in their genetic composition. These
results are consistent with the genetic distance among populations from the UPGMA
dendrogram (r = 0.84, data not shown). The genetic similarity between some trees
stresses the need to continue the study with a higher number of molecular markers
that allows an unequivocal identification of all trees.
This is a preliminary study as a basis of knowledge of the genetic variability
pattern of H. impetiginosus in the Argentine Yungas Rainforest to guide domestication, breeding, and conservation purposes. As general conclusions, Río Seco, Pocoy,
and Burruyacú populations should be prioritized according to their higher genetic
diversity and differentiation levels, and conservation measures (including ex situ
strategies) should be implemented. San Pablo and Rosario de la Frontera populations have an important value due to their genetic diversity levels despite its low
number of sampled trees. Some populations have an additional value because of
their important geographical position. Rosario de la Frontera connects NorthCentral with Southern Yungas, and Huasapampa and Lules are on the southern edge
of natural range of the species, and they could have an adaptive value. Future studies
increasing both sample size and number of markers are needed for more conclusive
results.
L. F. Fornes et al.