[MARMAM] New publication: Were the Madeira River rapids a geographical barrier to the boto (Cetacea: Iniidae)?

Waleska Gravena walpeixeboi at gmail.com
Mon May 12 18:46:02 PDT 2014

Dear Marmam friends,

My coauthors and I are pleased to announce the online publication of our
recent investigations of river dolphins in Madeira River Basin
(Amazon) in Conservation

Gravena W, Farias IP, da Silva MNF, da Silva VMF, Hrbek T (2014) Looking to
the past and the future: were the Madeira River rapids a geographical
barrier to the boto (Cetacea: Iniidae)? Conservation Genetics. Vol 15 (3):

ABSTRACT: In the present study we tested if a series of 18 rapids on the
upper  Madeira River form an effective barrier to gene flow, and in
particular if they delimit the distribution of the boto Inia
boliviensis—which it is believed to occurs only in the Bolivian sub-basin,
above the rapids—and I. geoffrensis, which occurs throughout the Amazon
basin and below the upper Madeira River rapids. We analyzed 125 individuals
from the Madeira River basin sampled from upstream and downstream of the
rapids. As the two species are morphologically similar, we used diagnostic
molecular characters from known reference specimens to assign individuals
to species. We observed that all individuals of Inia from the Bolivian
sub-basin up to almost the mouth of the Madeira River belong to the species
I. boliviensis. Therefore we concluded that the rapids do not delimit the
distribution of I. boliviensis upstream and I. geoffrensis downstream of
the rapids as previously hypothesized. Since we registered I. boliviensis
along almost the entire length of the Madeira River, we estimated gene
flow, time of divergence and effective population sizes of the upstream
(Bolivian) and downstream (Madeira River) groups of I. boliviensis using
IMa2. We concluded that gene flow is uni-directional from the upstream to
the downstream group. Divergence time between the two groups was estimated
to have occurred
*122 thousand years ago. The coalescent effective population size for the
upstream group was estimated at *131 thousand individuals, while for the
downstream group it was estimated at*102 thousand individuals. Recently two
dams have been constructed in the region of the rapids; neither has
a mechanism that will maintain connectivity between the upstream and
downstream regions, and together with anthropogenic alterations to the
hydrodynamic regime and ecology of the river will likely pose serious
long-term and short-term consequences for I. boliviensis and other aquatic

A PDF copy of this paper is available by request from
walpeixeboi at gmail.com<lizhartel at gmail.com>
.  <jmstraley at uas.alaska.edu>
Waleska Gravena, Dra.
Laboratório de Evolução e Genética Animal - LEGAL
Universidade Federal do Amazonas - UFAM

Associação Amigos do Peixe-Boi - AMPA
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