Thesis (M.Sc.)--Chulalongkorn University, 1997

Intraspecific genetic diversity of 90 individuals of Chelonia mydas collected from the Andaman Sea and the Gulf of Thailand was analysed using 3 microsatellite loci (Cm3, Cm72 and Cc117). Surprisingly, high genetic polymorphism in this endangered species was found. Thirty-one, 40 and 19 alleles were examined from PCR-amplification of C. mydas DNA with microsatellite primers Cm3, Cm72 and Cc117, respectively. The average heterozygosity was 0.87, 0.85 and 0.74 for Cm3, Cm72 and Cc117, respectively. Genetic distance between C. mydas population of the Andaman Sea and the Gulf of Thailand was 0.2693. The FST value calculated from microsatellite data indicated significance in population differentiation. Gene flow level of this species was high (Nm=40). Geographic heterozygosity test showed significant difference in allele frequency distribution (p=0.0012). This coupling with the FST analysis in juveniles illustrated that genetic population structure does exist in this species. Multiple paternity was found in this study using combined exclusion ability of all three investigated microsatellite loci. Based on six offspring, it was found that at least two males multiple-copulate with the female. The basic information for genetic population structure of C. mydas in Thailand and multiple-paternity of were very important for understanding their biological behaviour. These knowledge can be applied to construct sensible conservation programmes of this C. mydas and the others.