Genetic cryptic species as biological invaders:: the case of a Lessepsian fish migrant, the hardyhead silverside Atherinomorus lacunosus

Marine cryptic species, taxa that are morphologically identical but genetically distinct, may be important and underestimated components of the ecosystem. The understanding of several ecological interactions, such as marine bioinvasions, could be altered by the correct description of the bioinvaders. Here, we have focused our study on the hardyhead silverside, Atherinomorus lacunosus, a Lessepsian migrant. Lessepsian migrants are those species that are invading the Mediterranean from the Red Sea via the Suez Canal. We PCR amplified and sequenced the mitochondrial control region from individuals collected from the Mediterranean and the northern and southern Red Sea. We found that the two Red Sea populations are likely to correspond to two previously undescribed cryptic species. We also found that the Mediterranean individuals group with the northern Red Sea species. The Mediterranean population showed high levels of genetic diversity and did not share haplotypes with the northern Red Sea population. Lessepsian invasion by A. lacunosus probably occurred repeatedly and is likely to still be occurring. (C) 2002 Elsevier Science B.V. All rights reserved.