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Therefore of 33 individuals, four exemplars (12.12 %) could be migrants, or descendents of
migrants, of other lagoons.
The two completed AMOVA showed interesting and complementary results to those
generated with other analyses.
Table 4. Two different AMOVAs carried out with the pink river dolphin populations
analyzed in the Napo-Curaray Rivers at the Peruvian Amazon. A. With three
hierarchical geographic levels. B. With four geographical levels. * = significant
probabilities at the 0.05 significance levels.
A.
AMOVA
Percentage of
variation
Sourceof variation
Significance
Among populations (lagoons)
-0.4549
1.000
F
ST
= - 0.0045
Among individuals, within populations 26.0672
0.0000*
F
IS
= 0.2595
Within Individuals
74.3877
0.0000*
F
IT
= 0.2561
B
Among rivers (Napo & Curaray)
2.5115
0.1730
F
CT
= 0.0251
Among populations within rivers
-1.1034
0.5894
F
SC
= -0.0113
Among individuals within populations 25.5838
0.0000*
F
IS
= 0.2595
Within Individuals
73.0081
0.0000*
F
IT
= 0.2699
In the first analysis, three hierarchical geographical levels were employed (Table 4). The
differences among the lagoons were basically inexistent (Percentage of variation = -0.00455
%, p = 1.0000). However, a significant variance fraction was estimated among the individuals
within the lagoons (26.0672 %, p = 0.0000), although the highest variance fraction was within
the individuals (74.3877 %, p = 0.0000). Thus, although in the previous analyses certain
genetic differences were found among the pink river dolphins of diverse neighbor lagoons,
this analysis showed that all the little populations sampled, in this 280 km transect belonged
to a unique global gene pool and that the main genetic differences were among the individuals
independently of their geographical origins. The previous analyses and the current one could
be conciliated if we consider the following. All the animals sampled in the eight points
belonged to the gene pool for the nine microsatellites analyzed. Therefore, no strong genetic
differences could be found among these samples (AMOVA). However, the population size of
each lagoon was quite small. No more than 10-12 animals and, in many cases, we sampled all
the animals present in those lagoons (for instance, lagoons 6, 7 and 8). With these population
sizes, genetic drift could be intense. Significant genetic differences could exist among dolphin
groups of different lagoons, when they were taken together, although they belonged to the
same gene pool (exact tests and F
IS
statistics for the different microsatellites employed). If the
action of gene drift is stochastic with regard to spatial patterns, then the major fraction of the
genetic differences was among the individuals and not among other geographic levels
considered. The second AMOVA considered a fourth hierarchical level, the existence of two
different rivers, Napo and Curaray (two sampling points in the Napo River and six sampling
points in the Curaray River). This analysis revealed that the differences of the two rivers and
the differences of the lagoons within these two rivers were practically insignificant
(Percentage of variation = 2.5115 %, p = 0.1730 and -1.1035 %, p = 0.5894). Again, the
variance fraction among individuals within lagoons and, especially, the differences within
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