Abstract:
The phylogenetic relationships among selected Metapenaeus shrimp species and some genuses of the family Penaeidae from the east coast of Thailand and from the GenBank database were examined using partial sewuences of mitochondrial 16S rRNA (429 bp) and COI (741 bp) phylogenetic tree building metlding metnods, Maximum Parsimony (MP), Neighbor-Joining (NJ) and Maximum Likdlihood (ML). The COI gene in this study revealed higher levels of polymorphism than 16S rRNA gene (nucleotide diversity = 0.115 and 0.159 for 16S rRNA and COI genes respectively1). Also, the COI gene had higher resolution to differentiate closely-related species (GTR genetic distance values between Metapenaeus tenuipes and M. Brevicornis = 0.018 and 0.122 for values calculated from COI and 16S rRNA genes, respectively). At a genus level, most phylogenetic trees suggested two clades, (1) Metapenaeus + Parapenaeopsis+ Trachypenaeus และ (2) Fenneropenaeus + Penaeus + Litopenaeus + Masupenaeus + Melicertus. All analyses for both for both genes did not agree on phylogenetic relationship within some genuses. Molecular data supported the clustering of species within some genuses, namely Metapenaeus, Fenneropenaeus and Litopenaeus but did not support those of genuses Marsupenaeus, Melicertus, Trachypenaeus and Parpenaeopsis. Within genus Metapenaeus (bootstrap values = 66-99%), most closely related species included (1) M. brevicornis and M/ tenuipes (all topologies) and (2) M. ensis and M. affinis (COI gene). Metapenaeus moyebi was most distanty related to other Metapenaeus species. The results provided fundamental knowledge for investigation of biology and ecology of Metapenaeus spp.