The giant tiger prawn {Penaeus monodon) was collected from 11 different sites throughout its range (Kenya—>Indo china—»Philippines). Individuals were analyzed for allozyme (46 loci) and mtDNA restriction fragment length polymorphisms (RFLPs) using 5 restriction enzymes. The average heterozygosity calculated from the allozyme data H = 0.027 (0.020-0.032) was similars to other studies on decapod crustacean. In total 10 polymorphic (p 0.99) loci were observed several of these {AAT-1 , ALAT*, GPI, IDHP , MDH-1 , MPI and PGM”) contributing to significant differences in allele and genotype frequencies between populations. No significant differences were observed between samples collected at the same site in different years and no significant differences in HWE were observed within any single population. Genetic difference between all populations F^,=0.384 was high but was much smaller for SE Asian populations alone F, =0.014. The allozyme data suggested that the P. monodon populations structure could be divided into 4 main groups: Kenya, Philippines, Andaman Sea, and South China Sea.
The mtDNA genome was estimated to be 15.76±.57 kb. Only four enzymes could be reliable used (BamHI, EcoKV, PvuII and SacI) which gave 12 mtDNA haplotypes (Kenya population not included). Significant differences between haplotype frequencies were observed between the Andaman Sea and South China Sea populations. Nucleotide divergence data suggested two main clonal forms of mtDNA were present in SE Asian populations. These clones appear to have diverged gene 0.1-0.7 million years ago. Clone A was more common in Andaman Sea population whereas Clone B was more common in South China Sea.
Both techniques suggested that P. monodon can be subdivided into at least 3 isolated groups: Kenya, Andaman Sea, and South China Sea populations. This pattern of isolation we see today may be a relic of past separation during the last glaciation. Which has been modified by recolonization of new areas as the sea levels rose and present day patterns of gene flow caused by prevailing current patterns.