Judul: Phylogenetic relationships and genetic population structure of giant clams (Tridacna crocea and tridacna maxima) in Indonesia
Abstrak: There is an increasing concern that heavy-exploitation of marine populations ature populations of giant clam at high risk, leading to long-term consequences to· conservation and fisheries management. Information concerning taxonomy, s tematic, genetic population structure and connectivity of populations are vital for s tial arrangement of marine protected areas (MPAs) and fisheries management fa tne species. However, there is an uncertainty about the relationships between s c·es of Tridacnidae, in particular between species that belong to Chametrachea s· . genus; T. crocea, T maxima and T squamosa, resulted from several studies u.. g different genetic marker and not much is known about connectivity of marine p pulations in the Indonesian Archipelago. This study was carried out in order to el cilfate about the relationships among giant clam species, population structure of crocea and T. maxima, distribution pattern, and connectivity of those giant clam populations across the Indonesian Archipelago. Here we use fragment of 454 bp of the itocnondrial DNA cytochrome c oxidase I gene from T crocea, T maxima, T squamosa, T gigas and several sequences from GenBank as the out groups. The analysis of population structure of T crocea is based on 456 bp fragment of the cytoc::hrome oxidase I gene from 300 individuals collected from 15 localities across the Inda-Malay Archipelago, whereas for T maxima based on 484 bp fragment of the c::ytochrome c oxidase I gene from 211 individuals collected from 14 localities across the Indonesian Archipelago and the Red Sea. The result showed that giant clams formed a monophyletic group. Within Tridacna group, T crocea was closely related to T squamosa than to T maxima and formed monophyletic group. T crocea and T squamosa were sister taxa and sister group to T maxima and T. gigas. T. crocea shows a very strong genetic population structure and isolation by distance, indicating restricted gene flow among almost all sample sites. The observed Cl>₅rvalue of 0.28 is very high compared to other studies on giant clams. According to the pronounced genetic differences, the sample sites can be divided into five groups from West to East: (1) Padang, (2) Java Sea, (3) Makassar Strait (inclwding northern Borneo), (4) eastern coast of Sulawesi (including Sembilan, Komodo, and Kupang), and (5) Biak. This complex genetic population structure and pattern of connectivity can be attributed to the geological history and prevailing current regimes in the Inda-Malay Archipelago. T maxima showed a very strong genetic population structure but limited isolation by distance, indicating restricted gene flow is only among a few sample sites. The observed Cl>₅rvalue of 0.74 is very high compared to other studies on giant clams, even higher than such value in T crocea (0.28) According to the pronounced genetic differences, the sample sites can be divided into four groups from West to East: (1) the Red Sea, (2) Padang (Indian Ocean) and Java Sea, (3) Sulawesi (including Sangalaki, Komodo, and Kupang), and (4) Biak (Western Pacific).
Keyword: Phylogeny, Giant clam, Genetic structure, Population