GENETIC POLYMORPHISM AND POPULATION STRUCTURE OF THE STRIPED DOLPHIN, STENELLA COERULEOALBA,AND THE COMMON DOLPHIN, DELPHINUS DELPHIS, WITHIN THE ACCOBAMS AREA

摘要

The aim of the present work is to evaluate the genetic polymorphism of various populations of the common dolphin (Delphinus delphis) and the striped dolphin (Stenella coeruleoalba) in the Mediterranean Sea and north eastern Atlantic. The effort to estimate genetic diversity was achieved with the use of microsatellite DNA as a molecular genetic marker. A total of 156 were screened representing 3 Mediterranean populations (western Med, eastern Med and Korinthiakos Gulf) and one from the north east Atlantic Ocean. Five polymorphic cross-species microsatellites were tested (15-25 alleles). H_exp was higher than the H_obs in all populations at all loci. Unbiased estimates of Hardy-Weinberg exact P-values, using the Markov chain method, indicated a heterozygosity deficit (P<0.01). The proportion of randomisations gave a larger F_SThan the observed (P<0.01) and the values of F_ST were quite low (0.018 + 0.014) within the Mediterranean Sea. Relatively quite high levels of gene flow values (mean/V_m=2.45) were estimated among populations, despite the significant heterogeneity in allele frequencies. These N_m values were sufficiently high to imply near-panmixia between populations, indicating the possibility of a probable movement of migrants within the Mediterranean Sea and this is consistent with Nei's minimum genetic distance; D didn't show any clear spatial separation between western and eastern Mediterranean Sea. The most distant population was that from the north eastern Atlantic.