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al. (2000) and Garza & Williamson (2001) for microsatellites. This population suffered a
strong bottleneck from its origin until its population expansion, which happened very
recently, sometime during the last 5000 years. Although in this work, I did not analyze the
Orinoco River's dolphin populations, two Amazonian lineages colonized, at different times
within the Orinoco basin. The oldest Orinoco lineage diverged from the main Amazon
haplotype between 7,800
+
850 to 52,600
+
5.100 years ago ( = 0.388
+
0.042 and = 2.605
+
0.251, respectively), whereas the most recent lineage began between 5,400
+
600 to 7,800
+
600 years ago ( = 0.269
+
0.029 and = 0.388
+
0.029, respectively). Therefore, at least,
two paraphyletic molecular lineages of
Inia
are living together in the Orinoco basin. Thus a
sub-specific nomenclature (
Inia geoffrensis humboldtiana
) for the Orinoco
Inia
seems to not
be valid.
Figure 2. Median Joining network with the mtDNA control region haplotypes of pink river dolphins
proceeding from the Amazon (haplotypes in yellow), Bolivian Amazon (haplotypes in blue) and
Orinoco (haplotypes in red) basins. Clearly, the Amazon haplotypes were in the origin of the haplotype
expansion, meanwhile the Bolivian haplotypes derived from the central Amazon haplotype and two
independent Orinoquian haplotype lineages derived from the Amazon haplotypes.
D
ISCUSSION
This means that in each river (and for the total upper Amazon) a small, or several small,
dolphin propagules gave origin to the current populations with a rapid and/or a recent growth
of these populations. The social system in small populations, detected by Ruiz-García (2010a)
for this species, helps us to understand why small genetic lineages colonized the Amazonian
rivers step by step instead of a single, or a few massive migration(s). The results were
basically the same for all the rivers studied in Peru and Bolivia (representing the rivers of
these both countries, two different and independent colonization processes) which showed
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