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Overall, haplotype and nucleotide diversities for the mitochondrial DNA control region in
Sotalia fluviatilis
are similar to those reported for species with similar distributions and
habitat ranges, including the Antillean and Amazonian manatees (García-Rodríguez
et al
.
,
1998; Vianna
et al
.
, 2006) and the Amazon River dolphin
Inia geoffrensis
(Banguera-
Hinestroza et al
.
, 2002). However, although both Amazon River dolphin species present some
degree of phylopatry, recent data (Vianna et al
.
2010, this topic) for the pink dolphin (
I.
geoffrensis
), collected in the same Brazilian region as
S. fluviatilis
sampled here, indicate that
the former species is highly structured, even in a microgeographic scale. As
S. fluviatilis
may
have a much more recent origin as species in the Amazon, the spatial differentiation of
populations is less pronounced but it is underway.
Implications for
Sotalia
Fluviatilis Conservation and Management
As can be observed in our results, gene flow appears to be higher for
S. fluviatilis
than
S.
guianensis
(Caballero, 2006)
,
at least among the Amazon regions included in our study. As
can be observed in our results, gene flow appears to be high between the regions included in
our study. For this reason, priority should be given to maintain this connectivity. Obstacles to
connectivity could affect these population units and therefore, hydroelectric and dam
constructions must be evaluated, depending on the region where they intend to be developed,
taking into consideration the distribution of
S.
fluviatilis
and other aquatic mammals and
reptiles in the region, as well as routes in fish migration and abundance of prey items to
sustain these groups (Smith & Smith, 1998). Boat traffic and fishery interactions must also be
determined along the Amazon and most of its channels and tributaries, as has been done by
researchers in the Colombian Amazon (Trujillo
et al
.
, 2000; Diazgranados
et al
.
, 2002). As
our data have also shown, genetic differentiation is higher in the extremes of the distribution
of the Amazon species, thus its conservation strategy should also take into account the
relative isolation of some populations. Local takes will result in local extinction but
connectivity could mask a wider decline (Taylor, 1997). This would require greater regulation
and law enforcement of both commercial and artisanal fisheries. Regulation of these activities
and improvement of fishing practices needs to be implemented with involvement of the local
communities.
A
CKNOWLEDGMENTS
We are grateful to all the people and institutions that gave us access to samples for this
study: J. G. Mead and C. Potter (United States Smithsonian Institution National Museum of
Natural History), R. L. Brownell Jr., students and researchers at Fundación Omacha
(Colombia), IBAMA (Brazil), the DNA Archive (NMFS Southwest Fisheries Science Center)
and the Fondo para la Accion Ambiental (US-Aid) (120108-E0102141; Structure and Genetic
Conservation of river dolphins,
Inia
and
Sotalia
, in the Amazon and Orinoco basins; project
granted to the Pontificia Universidad Javeriana-M. Ruiz-García). All Brazilian samples were
collected with the government permit IBAMA 131/2004. This research was developed
according to the special authorization for access to genetic resources in Brazil # 03/2004
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