AMAZON RIVER DOLPHIN: HIGH PHYLOPATRY DUE TO RESTRICTED DISPERSION AT LARGE AND SHORT DISTANCES - Biology, Evolution and Conservation of River Dolphins Within South America and Asia - page 102

Keywords : Phylopatry, Inia geoffrensis , mtDNA, phylogeography.

I NTRODUCTION

The Amazon River Dolphin or Pink Dolphin ( Inia geoffrensis ) is endemic to the Amazon
and Orinoco rivers and their tributaries, distributed in a total range area of seven million km 2
(Best & da Silva, 1989). The species is classified as vulnerable by The World Conservation
Union (IUCN) and listed in Appendix II of the Convention on International Trade in
Endangered Species of Wild Flora and Fauna (CITES). The major threats include the
incidental catch of I. geoffrensis by fishing nets and the recent construction of dams (da Silva
2002). Presently, the Amazon River Dolphin is also hunted for the extraction of its genital
organs which are sold as magical amulets (Best & da Silva, 1989). Furthermore, the species
seems to also be affected by chemical contamination, such as pesticides and mercury (Rosas
& Lehti, 1996).
Some previous studies (Cassens et al., 2000; Hamilton et al., 2001; Yan et al., 2005) have
focused on the phylogeny of the river dolphins ( Inia , Pontoporia , Lipotes , and Platanista ),
suggesting a paraphyletic relationship among the existent river species, indicating a high
adaptive plasticity for these cetaceans. However, few studies have investigated the population
structure and phylogeography of these species (Banguera-Hinestroza et al., 2002; Yang et al.,
2003).
A recent study (Banguera-Hinestroza et al., 2002) analyzed the mtDNA control region
and Cytochrome b gene haplotypes of Inia geoffrensis , supporting the proposal of a
subdivision of the Inia genus into at least two evolutionarily-significant units. It has also
showed a strong phylogeographic pattern at a macro-geographic scale. However, it did not
take into account the micro-geographic level to evaluate the species' capacity to migrate
through short distances.
In this chapter we have analyzed mtDNA control region sequences of Inia geoffrensis
from two close but ecologically different populations in Brazil to assess the spatial
distribution of genetic diversity and likely restrictions to gene flow. Besides, we compared the
population genetic structure in a macrogeographic scale with populations from other South-
American regions.

M ATERIALS AND M ETHODS

Sample Collection and DNA Extraction

Tissue samples were collected from 21 pink dolphins ( Inia geoffrensis ) from three
different locations within the central Amazon basin, Brazil. Eleven samples were collected
near the lake on the Mamirauá Sustainable Development Reserve (MSDR) referred here
simply as ―Mamirauá‖, nine in the Tef￩ River and Lake, referred as ―Tef￩‖, and one at an
intermediate area between the previous locations (Figure 1). These samples were collected
from captured and dead animals over a nine year period. Muscle and skin tissues were