Neotypification of the Sporolithon mediterraneum Heydrich (Sporolithales, Corallinophycidae, Rhodophyta) and the status of Sporolithon in the Mediterranean Sea

A neotype specimen is designated for the coralline alga Sporolithon mediterraneum Heydrich (Sporolithales, Corallinophycidae, Rhodophyta) and critically examined here, since the original holotype specimen apparently has been destroyed. The neotype specimen was collected in a mesophotic rhodolith bed near Gorgona Island (Tyrrhenian Sea, Mediterranean). Additional specimens were collected in a rhodolith bed in the Menorca Channel (Western Mediterranean) and were used to confirm the identification of the neotype. Molecular analyses of psbA and rbcL with all Sporolithon species for which there are currently sequence data, including S. ptychoides and S. molle supported the designation of this neotype and the circumscription of this Mediterranean species. Additional specimens from Menorca Channel were resolved as conspecific based on psbA sequences. The morphoanatomical data presented indicated that S. mediterraneum can be also distinguished from the type species Sporolithon ptychoides Heydrich and Sporolithon molle (Heydrich) Heydrich, the only two other species previously reported from the Mediterranean Sea, by the occurrence of 5–6 cell paraphyses and larger stalk cells. A consideration of the status of Sporolithon in the Mediterranean region is also discussed.