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These cases were as follows: In lagoon 4, Ev37 showed a homozygote excess (p = 0.0478
+ 0.0002); in the lagoon 7, MK5 and Ev37 yielded homozygote excess (p = 0.0290 + 0.0015
and p = 0.0337 + 0.0018, respectively) as well as did Ev37 in lagoon 8 (p = 0.0089 + 0.0010).
Thus, out 52 HWE tests only four were significant at the level of p < 0.05, which represents
7.69 % and did not significantly deviate from the 5 % error type. In fact, if I apply the
Bonferroni criteria, the significant probability level was 0.00096. In this case, no significant
homozygote excess cases were found in the lagoons sampled. Therefore, no evidence of
endogamy for Inia geoffrensis was found within any lagoon analyzed. When the F IS statistic
was considered in each sample point, some fraction was negative. In sample point 1, 20 %
(1/5) of polymorphic microsatellites presented a negative F IS (heterozygote excess). In lagoon
2, 16.67 % (1/6) of microsatellites analyzed yielded a negative F IS meanwhile in lagoon 4,
42.86 % (3/7), and lagoons 6, 7 and 8, 28.57 % (2/7), also showed negative F IS values. These
results were incompatible with endogamy in the little pink river dolphin populations studied
within the lagoons. If the nine microsatellites are studied for all the lagoons collectively, the
picture obtained is different (Table 3).
Table 3. Overall Hardy-Weinberg equilibrium exact probability tests (P) and standard
deviations (SD) for the nine DNA microsatellites studied. Six loci (*) showed homozygote
excess.
Marker
P
SD
EV76
0.00604*
0.00008
Homozygote excess
EV14
0.00342*
0.00005
Homozygote excess
KWM2b
1
0
KWM2a
0.00246*
0.0005
Homozygote excess
KWM12a
1
0
MK5
0.03316*
0.0016
Homozygote excess
PPHO 137
1
0
EV37
0.00000*
0
Homozygote excess
EV94
0.00447*
0.0006
Homozygote excess
Six microsatellites showed significant homozygote excess with positive F IS , Ev76 (p =
0.0060 + 0.00008), Ev14 (p = 0.0034 + 0.00005), KWM2a (p = 0.0025 + 0.0005), MK5 (p =
0.00332 + 0.0016), Ev37 (p = 0.0000 + 0.0000) and Ev94 (p = 0.0045 + 0.00006). This
means, and it is the first indication, that each lagoon had a pink river dolphin genotype
composition different from the other lagoons. Therefore, the homozygote excess detected at
six out of nine loci was caused by Wahlund effect (= population subdivision) and the gene
flow among the lagoons is not extensive enough to totally homogenize the gene composition
of all the lagoons analyzed.
Similarly, the assignation analysis showed the following situation. The individuals
sampled in the first sample point were grouped in its own cluster. The same was true for the
lagoons 2, 3, 5 and 8. All the individuals were correctly classified in their own lagoons.
Nevertheless, in lagoon 4, two individuals were more intensely associated with lagoons 6 and
7, respectively. In lagoon 6, one individual was significantly more clustered with lagoon 7 as
well as in lagoon 7 one individual was clearly associated with the individuals of lagoon 8.
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