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 105

correlation between genetic ( F ST or  ST ) and geographic distances. Geographic distances
among samples were calculated following the river's course in the Amazon basin using the
MapSource (Garmin®) software.
We also used the SAMOVA (Dupanloup et al., 2002) approach to identify groups of
geographically homogeneous populations and to maximally differentiate them from each
other. Groupings suggested by SAMOVA were further tested by AMOVA in Arlequin as
described above. Besides, we also used the software Barrier (Manni et al., 2004) to identify
likely barriers to gene flow using the haplotype distribution in populations spatially defined
by geographic coordinates. These tests were used to identify significant discontinuities in the
population structure of I. geoffrensis .
R ESULTS
Populations Phylopatry
A fragment of 519 base pairs (bp) of the mtDNA control region (HVSI) was sequenced in
21 Brazilian individuals. Seven polymorphic transitions were identified in the Inia geoffrensis
sequences from all the locations and we found a total of six control region mtDNA haplotypes
restricted to Brazil. Three haplotypes were found exclusively in individuals from the
Mamirauá Lake, and two in the Tefé River and Lake (Tefé). Another haplotype (BrC) was
identified in both locations and in one additional specimen in an intermediate area between
the two studied locations (Table 1).
The Mamirauá population shows a higher haplotype diversity than the Tefé population
(Table 1). Although the two localities are only about 45 km apart (straight line between their
edges), a high differentiation was found between the two studied populations ( ST (TN+Γ) =
0.66, F ST = 0.38), sharing only one haplotype (BrC). AMOVA analysis (using  ST (TN))
shows that most of the variation is observed between the localities (65.7%), but there is still a
considerable amount of variation within each locality (34.3%). Despite the observation of
negative values, significant expansion could not be detected for Mamirauá or Tefé
populations with Tajima's and Fu's tests. Mismatch distributions analyses also showed no
sign of population expansion.
The Median Joining Network (MJN) shows two population clusters in Brazil (Figure 2).
The star-like tree found for the Mamirauá population showing an excess of rare haplotypes
originated from the most frequent haplotype (BrC) could suggest population growth, however
it has been considered non significant by previous expansion tests. The haplotypes from the
Tefé population are more differentiated. This is also supported by the mismatch distribution
analysis that presented unimodal distribution for Mamirauá and bimodal for Tefé (Figure 3),
and by the slightly higher nucleotide diversity observed in Tefé (Table 1).
The complete Cyt-b gene (1140 bp) was also sequenced in 20 individuals from the
Brazilian Amazon. Two different haplotypes were distinguished, differentiated by one
transversion (non-synonymous). One haplotype (BrM) appears in 13 individuals from
Mamirauá and another one appears in 7 individuals from Tefé (BrT). Thus, there is a specific
Cyt-b haplotype found in Tefé and another found in Mamirauá, even though they are only 45
Km apart. This emphasizes the remarkable population structure that was already suggested by