Biology Reference
In-Depth Information
I
NTRODUCTION
The micro-genetic structure in mammals, and other vertebrates, is very difficult to
analyze because the sampling level for it is not very easy to obtain by the researcher. In the
case of mammals, only a few examples of micro-geographic genetic structure have been
published considering the larger number of species the category of mammals contains and the
importance of micro-genetic structure (
Alouatta seniculus
, Pope, 1992;
Balaenoptera
borealis,
Kanda et al., 2006;
Cercopithecus aethiops
, Cheney & Seyfarth, 1983;
Cynomys
ludovicianus
, Chesser, 1983;
Dypodomys spectabilis,
Waser & Elliot, 1991;
Felis catus
,
Ruiz-García, 1998; 1999, Say et al., 2003;
Macaca mulatta
, Melnick et al., 1984;
Marmota
flaviventris,
Schwartz & Armitage, 1980; Armitage, 1988;
Microtus pennsylvanicus
, Sheridan
& Tamarin, 1986;
Mus musculus musculus
, Dallas et al., 1995;
Oryctolagus cuniculus
, Daly,
1981;
Petrogale xanthopus
, Pope et al., 1996;
Phocoena phocoena
, Andersen et al., 1997;
Rangifer tarandus
, Cote et al., 2002;
Spermophilus richardsonii
, van Staaden et al., 1994).
This was not a comprehensive list, but it does name the more outstanding studies. No micro-
geographical genetics studies have been carried out with a river dolphin because it is not easy
to obtain samples of these organisms. However, we caught, 33 pink river dolphins (
Inia
geoffrensis
) with large nets in a 280 km transect across seven lagoons, and in one beach, of
the Napo-Curaray river basin within the Peruvian Amazon. This represented a unique
opportunity to study the possible genetic structure of this species at a very fine geographic
level incorporating social reproductive parameters. To do this, nine DNA microsatellites
(short tandem repeat polymorphisms; STRPs) were applied to all the pink river dolphins
captured in the Napo and Curaray rivers. These markers are based on the polymerase chain
reaction (PCR) methodology. Microsatellites are composed of tandem, repetitive units of two
to six base pairs in length (Weber and May, 1989). STRPs are randomly distributed, highly
polymorphic and frequently found inside eukaryotic genomes. Therefore, they are an
important tool in the study of population biology dynamics (Bruford & Wayne, 1993). All of
these facts have contributed to the use of STRPs to construct genetic recombination maps in
different species and to apply them to diverse population and systematic studies. Several
examples are as follows: 1- To determine social structure in several wild species (for instance,
in some cetaceans as
Megaptera novaeangliae,
Amos et al., 1993); 2- To determine paternity
diagnoses in a vast range of animal species (from chimpanzee populations, Morin et al., 1993,
to
Drosophila
populations, Noor, 1995); 3- To determine possible bottleneck events in wild
species (for example in
Canis simensis,
Gottelli et al., 1994, in the Australian wombat,
Lasiorhinus krefftii,
Taylor et al., 1994 or in the upper Amazon populations of Humboldt
woolly monkey,
Lagothrix lagotricha
, Ruiz-García, 2005); 4- To determine pure lineages or
even possible new species (for instance, the existence of pure lineages of the Mexican gray
wolf,
Canis lupus bayileyi,
Garcia-Moreno et al., 1996, or possible different chimpanzee
species, Morin et al., 1994). Herein, I applied STRPs to accrue new evidence about the
possibility of a consistent social reproductive system in
Inia geoffrensis
and to determine its
possible genetic structure at a micro-geographical level within a determined river basin. This
is important because cetacean ecologists are trying to determine if pink river dolphins have a
social system or if they really are solitary animals without social structure. The ethological or
ecological studies are ambiguous in this sense. The pioneer works of Trebbau & Van Bree
(1974) and Pilleri & Gihr (1977), suggested that groups of these dolphins showed
Search WWH ::
Custom Search