GENETIC POPULATION STRUCTURE OF DUSKY DOLPHINS (LAGENORHYNCHUS OBSCURUS) ALONG THE ARGENTINA COAST BASED ON MTDNA

LOIZAGA DE CASTRO, ROC¨ªO; HOELZEL, A. RUS; CRESPO ENRIQUE A.

Florianópolis

Congreso; XIV Reunion de Trabalho de Especialistas em Mamiferos Aquáticos da América do Sul (RT)eros Aqu¨¢ticos da Am¨¦rica do Sul (RT); 2010

Sociedade Latinoamericana de Especialistas em Mamíeros Aquáticos

During the 90´s, important levels of incidental mortality were recorded for dusky dolphins (Lagenorhynchus obscurus) in purse seine and trawling fisheries along the Argentine coast. Minor impacts were added by dolphin-watching activities. However, the link between populations along the coast subject to different types and intensities of impacts is unknown. Within this frame is indispensable to assess the genetic structure of the population. Skin samples were collected using skin swabbing and biopsy techniques, preserved in DMSO 20% saturated NaCl, from 4 localities, throughout the distribution range in the Atlantic. A fragment of 750pb of the CrMtDNA was sequenced for 150 samples. Sex was determined by molecular techniques and parity among sexes was tested using a X2. Haplotypes genealogy was evaluated building a consensus tree using the Kimura 2 parameter model. Population structure was estimated by the Fst and ¦µst statistics and AMOVA in Arlequin v3.1. A population expansion analysis was performed calculating Tajima¡¯s D and Fu¡¯s F statistic and performing a mismatch analysis. Sex ratio was not different from parity (X2 df= 1, p0.001). The haplotypic diversity was 0.93 and 31 haplotypes were defined. The overall nucleotide diversity was estimated at 0.1449 (SE= 0.0933161). The nucleotide diversity for every sampling location was in the same order of magnitude, ranging from 0.076935 to 0.281928. The AMOVA indicates that 82% of the molecular variance is found within the putative populations. Nevertheless, 18% of the remaining variance among populations is highly significant (p<0.001). The mismatch analysis is consistent with the Tajima¡¯s D and Fu¡¯s F statistics (both non significant for every population). The population as a whole shows no signature of expansion. MtDNA analysis detected 2 main populations along the coast, the northern (GSM, GSJ) and the southern populations (GN, GSJOR) being Peninsula Vald¨¦s the geographical border.