Not so Lessepsian migrants of the Spirobranchus tetraceros complex (Serpulidae, Annelida)

Spirobranchus tetraceros (Schmarda, 1861), originally described from New South Wales, Australia, was later reported as a widely distributed successful species of Indo-Pacific origin, including as Lessepsian migrant to the Mediterranean, until evidence has accumulated that the nominal taxon is a large complex of morphologically similar species. Specimens of Spirobranchus cf. tetraceros recently discovered in the Western Mediterranean (Valencia, Spain) morphologically resembled those of S. multicornis from the Red Sea rather than S. tetraceros sensu stricto from Australia. However, genetic studies proved that sequences of the introduced specimens match neither those of the S. tetraceros morphotype from warm temperate Australia (NSW) nor those of S. multicornis from the Red Sea. Subsequently, Kupriyanova et al. (2022) designated a neotype of S. tetraceros from New South Wales supported by DNA sequence data and demonstrated that several species of the S. tetraceros complex exist in Australia alone. This study examined several populations of the S. tetraceros complex world-wide in search of the source population for the Western Mediterranean invader and demonstrated its identity with S. arabicus widely distributed in the Persian (Arabian) Gulf.