357
13.2.3 Molecular Evidence of Hybrid Zones of Cedrela
in the Yungas
The inclusion on molecular genetics studies of the third species of Cedrela (C. saltensis) with natural distribution in the Yungas allowed us to investigate whether natural hybridization took place among Cedrela species in NWA, thus supporting the
existence of hybrid zones between them (Zelener et al. 2016).
Species delimitation in Cedrela is difficult because of the lack of unique qualitative morphological diagnostic characters. They can be defined only by reference to
six widely variable and overlapping characters (Pennington and Muellner 2010).
Therefore, a combined dataset of AFLP markers and ITS (internal transcribed spacers) sequences data were used to test hybridization and/or introgressive hybridization in Cedrela species from the Yungas of NWA. For this study, 210 samples were
available, including the three Cedrela species that occur in Yungas: (i) 104 samples
from 10 populations of C. angustifolia; (ii) 84 samples from 8 populations of
C. balansae; and (iii) 22 samples from 2 populations of C. saltensis located in zones
of sympatry between C. saltensis and C. angustifolia and between C. saltensis and
C. balansae in Calilegua National Park and San Andrés farm, respectively
(Table 13.1; Fig. 13.1). For detailed information about AFLP and ITS procedures
and data analyses, see Zelener et al. (2016).
13.2.3.1 Population Structure of Cedrela in the Yungas
AFLP fingerprinting of the 210 samples of Cedrela from the Yungas resulted in a
matrix of 577 well-scorable polymorphic markers, which was analyzed by 2 complementary methods: (i) a multivariate approach as Principal Coordinates Analysis
(PCoA) using GenAlEx 6.3 (Peakall and Smouse 2006) and (ii) a statistical inference based on the Bayesian clustering method of Structure 2.3.4 (Pritchard et al.
2000; Falush et al. 2007).
The PCoA showed that most of the samples grouped according to the species:
there was a main cluster for each of the three species (C. angustifolia, C. balansae,
and C. saltensis). The first principal coordinate (73.1% of the total variation) clearly
distinguished samples of C. angustifolia from samples of the other two species. The
second principal coordinate (14.8% of the total variation) grouped most of the samples of either C. saltensis or C. balansae in separate groups. However, some samples of these two species showed intermediate positions between C. saltensis and
C. balansae clusters. The scattering was most noticeable for samples from
Pintascayo, San Andrés, Acambuco, and Calilegua National Park populations of
C. balansae. Remarkably, most samples of Pintascayo rested near the C. saltensis
cluster (complete data shown in Zelener et al. 2016).
In Structure, a preliminary analysis using data from the three species (20 populations) revealed that the 210 samples of Cedrela split into two clusters (best
K = 2). One of the clusters was congruent with a taxonomical-delimited species,
13 Patterns of Neutral Genetic Variation for High-Value Cedar Species…
13.2.3 Molecular Evidence of Hybrid Zones of Cedrela
in the Yungas
The inclusion on molecular genetics studies of the third species of Cedrela (C. saltensis) with natural distribution in the Yungas allowed us to investigate whether natural hybridization took place among Cedrela species in NWA, thus supporting the
existence of hybrid zones between them (Zelener et al. 2016).
Species delimitation in Cedrela is difficult because of the lack of unique qualitative morphological diagnostic characters. They can be defined only by reference to
six widely variable and overlapping characters (Pennington and Muellner 2010).
Therefore, a combined dataset of AFLP markers and ITS (internal transcribed spacers) sequences data were used to test hybridization and/or introgressive hybridization in Cedrela species from the Yungas of NWA. For this study, 210 samples were
available, including the three Cedrela species that occur in Yungas: (i) 104 samples
from 10 populations of C. angustifolia; (ii) 84 samples from 8 populations of
C. balansae; and (iii) 22 samples from 2 populations of C. saltensis located in zones
of sympatry between C. saltensis and C. angustifolia and between C. saltensis and
C. balansae in Calilegua National Park and San Andrés farm, respectively
(Table 13.1; Fig. 13.1). For detailed information about AFLP and ITS procedures
and data analyses, see Zelener et al. (2016).
13.2.3.1 Population Structure of Cedrela in the Yungas
AFLP fingerprinting of the 210 samples of Cedrela from the Yungas resulted in a
matrix of 577 well-scorable polymorphic markers, which was analyzed by 2 complementary methods: (i) a multivariate approach as Principal Coordinates Analysis
(PCoA) using GenAlEx 6.3 (Peakall and Smouse 2006) and (ii) a statistical inference based on the Bayesian clustering method of Structure 2.3.4 (Pritchard et al.
2000; Falush et al. 2007).
The PCoA showed that most of the samples grouped according to the species:
there was a main cluster for each of the three species (C. angustifolia, C. balansae,
and C. saltensis). The first principal coordinate (73.1% of the total variation) clearly
distinguished samples of C. angustifolia from samples of the other two species. The
second principal coordinate (14.8% of the total variation) grouped most of the samples of either C. saltensis or C. balansae in separate groups. However, some samples of these two species showed intermediate positions between C. saltensis and
C. balansae clusters. The scattering was most noticeable for samples from
Pintascayo, San Andrés, Acambuco, and Calilegua National Park populations of
C. balansae. Remarkably, most samples of Pintascayo rested near the C. saltensis
cluster (complete data shown in Zelener et al. 2016).
In Structure, a preliminary analysis using data from the three species (20 populations) revealed that the 210 samples of Cedrela split into two clusters (best
K = 2). One of the clusters was congruent with a taxonomical-delimited species,
13 Patterns of Neutral Genetic Variation for High-Value Cedar Species…