Preliminary data on the genetic structure of a highly successful invading population of oyster suggesting its establishment dynamics in the Levant

Biological invasions in the marine environment are a worldwide threat to native communities. The opening of the Suez Canal, which connects the Red Sea with the Mediterranean, resulted in the most invaded marine system in the world, causing dramatic ecological changes to the East Mediterranean Sea. One of the most prominent rocky benthos invertebrate invaders is the Indo-Pacific oyster Spondylus spinosus (family Spondylidae), first recorded along the Israeli coast in 1988. The biology and ecology of S. spinosus have not been studied in its native range or in the newly invaded one. We used field surveys to uncover the invasive oyster's current status and molecular tools to characterize some aspects of its genetic population structure, in search of clues to its invasion dynamics. We found that S. spinosus forms dense populations along the Israeli Mediterranean coast and reaches large shell sizes. Using two mitochondrial DNA markers, we confirmed that the invading species is identical to that found in the Red Sea. The genetic structure of the population at five sites along the coast reveals a total of seven haplotypes. The most common haplotype was the only one found in the northern Red Sea population, whereas one Mediterranean site (Sdot Yam) was particularly variable (five haplotypes). We conclude that S. spinosus has become well established in the Mediterranean following more than two decades since its first record there. We suggest that the Sdot Yam site is where the oyster was first established and where repeated introductions may since have occurred.