352
found. The Upper Bermejo River Basin (UBRB) in the northern edge of Yungas and
the wet slopes of Sierra de Aconquija towards the south may have been historical
refuges of the species. They hold the highest rainfall of the region due to their orography. This is in agreement with the two areas that have been suggested as potential
biodiversity refuges in Yungas due to its high levels of endemisms associated with
long-term ecosystem stability (Brown et al. 2006).
13.2.1.3 Genetic Variation and Anthropogenic Disturbance
In addition to latitudinal patterns, logging history of C. angustifolia populations
could also explain the genetic variability of the species in Yungas (Inza et al. 2012).
A loss of genetic diversity in forest tree species was observed with increasing logging intensity, and bottlenecks in disturbed populations are suggested as a possible
explanation (White et al. 1999; Kageyama et al. 2004; André et al. 2008).
To evaluate genetic variation patterns of C. angustifolia according to logging
history, its populations were classified into three different disturbance levels
(Table 13.2; see Inza et al. 2012 for classification criteria), and genetic diversity
(He, PPL, and EB) was then calculated for each disturbance group. To minimize the
effect of latitude, the disturbance groups were assessed within each latitudinal sector, and, finally, only pairs of neighboring populations with different disturbance
levels were compared.
A general trend of decrease in genetic diversity with increasing logging intensity
was observed (Inza et al. 2012). This was more evident in southern Yungas with the
undisturbed group showing the highest genetic diversity (He = 0.314, PPL = 82.3%,
EB = 22), followed by the low disturbed group (He = 0.138, PPL = 55.1%, EB = 11)
and the disturbed group showing the lowest values (He = 0.086, PPL = 24.5%,
EB = 2). Only in this subregion, genetic differentiation among disturbed group
(Φ RT , AMOVA, GenAlEx 6.2 Peakall and Smouse 2006) was significant (Table 13.3);
the fact that overexploitation of C. angustifolia began on southern Yungas (Minetti
2006) could be the explanation. Additionally, genetic erosion processes at this latitude could have a greater impact due to the lower initial levels of genetic diversity
(Inza et al. 2012). This is consistent with the assessment of neighboring populations
that showed lower genetic diversity for populations with higher disturbance for all
compared pairs (data shown in Inza et al. 2012) and a significant genetic differentiation (Φ PT ) among them (high in the south, low-moderate in the north and the center,
Table 13.3). For neighboring populations no selection pressure is expected, and
therefore, it was suggested that genetic drift processes are associated with reduced
effective population sizes (Young and Boyle 2000; Degen et al. 2006), which could
explain the loss of genetic diversity in logged populations (Inza et al. 2012). No
genetic differentiation between Baritú National Park and Empresa 3R pair of populations was observed, but the proximity between them and the unlogging period of
Empresa 3R population for more than 20 years may explain it.
N. Zelener et al.
found. The Upper Bermejo River Basin (UBRB) in the northern edge of Yungas and
the wet slopes of Sierra de Aconquija towards the south may have been historical
refuges of the species. They hold the highest rainfall of the region due to their orography. This is in agreement with the two areas that have been suggested as potential
biodiversity refuges in Yungas due to its high levels of endemisms associated with
long-term ecosystem stability (Brown et al. 2006).
13.2.1.3 Genetic Variation and Anthropogenic Disturbance
In addition to latitudinal patterns, logging history of C. angustifolia populations
could also explain the genetic variability of the species in Yungas (Inza et al. 2012).
A loss of genetic diversity in forest tree species was observed with increasing logging intensity, and bottlenecks in disturbed populations are suggested as a possible
explanation (White et al. 1999; Kageyama et al. 2004; André et al. 2008).
To evaluate genetic variation patterns of C. angustifolia according to logging
history, its populations were classified into three different disturbance levels
(Table 13.2; see Inza et al. 2012 for classification criteria), and genetic diversity
(He, PPL, and EB) was then calculated for each disturbance group. To minimize the
effect of latitude, the disturbance groups were assessed within each latitudinal sector, and, finally, only pairs of neighboring populations with different disturbance
levels were compared.
A general trend of decrease in genetic diversity with increasing logging intensity
was observed (Inza et al. 2012). This was more evident in southern Yungas with the
undisturbed group showing the highest genetic diversity (He = 0.314, PPL = 82.3%,
EB = 22), followed by the low disturbed group (He = 0.138, PPL = 55.1%, EB = 11)
and the disturbed group showing the lowest values (He = 0.086, PPL = 24.5%,
EB = 2). Only in this subregion, genetic differentiation among disturbed group
(Φ RT , AMOVA, GenAlEx 6.2 Peakall and Smouse 2006) was significant (Table 13.3);
the fact that overexploitation of C. angustifolia began on southern Yungas (Minetti
2006) could be the explanation. Additionally, genetic erosion processes at this latitude could have a greater impact due to the lower initial levels of genetic diversity
(Inza et al. 2012). This is consistent with the assessment of neighboring populations
that showed lower genetic diversity for populations with higher disturbance for all
compared pairs (data shown in Inza et al. 2012) and a significant genetic differentiation (Φ PT ) among them (high in the south, low-moderate in the north and the center,
Table 13.3). For neighboring populations no selection pressure is expected, and
therefore, it was suggested that genetic drift processes are associated with reduced
effective population sizes (Young and Boyle 2000; Degen et al. 2006), which could
explain the loss of genetic diversity in logged populations (Inza et al. 2012). No
genetic differentiation between Baritú National Park and Empresa 3R pair of populations was observed, but the proximity between them and the unlogging period of
Empresa 3R population for more than 20 years may explain it.
N. Zelener et al.