Nonindigenous species are considered among the major threats to biodiversity. A deep understanding of the processes underlying invasion is impeded, among others, by insufficient taxonomic and distributional knowledge. The Mediterranean Sea is experiencing a large invasion by Red Sea species as a result of the opening of the Suez Canal, at a rate which far exceeds those in any other open marine system. Here, we focus on a potential Red Sea marine invader into the Mediterranean, the mytilid Brachidontes pharaonis, as a case study, and review alternative explanations for its present distribution in the Mediterranean, Red Sea, and the Indo-Pacific. A previous study showed a significant difference in haplotype composition among the Mediterranean and the northern Red Sea and that most Mediterranean Sea haplotypes were unique (up to 80%). We present updated analyses using mitochondrial DNA (mtDNA) samples from the Persian Gulf (Arabian Sea) and compare them to populations in the Mediterranean, Red Sea, and Sri Lanka. We found that haplotypes collected in the southern Red Sea, Qatar, and Sri Lanka were significantly distinct from all those sampled in the eastern Mediterranean and northern Red Sea. In contrast, the haplotypes from Abu Dhabi, a large, active port, clustered within those from the Mediterranean Sea and the northern Red Sea. Together, the Persian Gulf and the Indian Ocean do not seem to be the sources of the Mediterranean and northern Red Sea populations. The presence of many haplotypes within the Mediterranean and northern Red Sea that are not traceable to other populations (apart from Abu Dhabi) suggests that B. pharaonis is not truly a nonindigenous to the Mediterranean but, rather, is a previously undetected indigenous species. The establishment of the Suez Canal may have brought together divergent lineages and resulted in an admixture of populations, but this scenario alone cannot explain the rich assembly of unique haplotypes in the Mediterranean Sea. Our results lead to a better understanding of the genetic structure of this species. The results of our study suggest that detailed empirical and careful evaluations are needed in order to resolve the correct origin of those classified as nonindigenous species.
|Title of host publication||The Arabian Seas|
|Subtitle of host publication||Biodiversity, Environmental Challenges and Conservation Measures|
|Publisher||Springer International Publishing|
|Number of pages||15|
|State||Published - 1 May 2021|