Laurencia mediterranea sp. nov. (Ceramiales, Rhodophyta) from the central Mediterranean Sea

The identification of macroalgal species within the Laurencia complex is challenging, due to the presence of inconspicuous morphological characters, extensive variation in these traits and a diverse biogeography. Moreover, for a number of these species, no DNA sequence data are available in online databases. For this study, five algal specimens, tentatively assigned to Laurencia, were collected from Malta in the central Mediterranean Sea and studied using an integrative systematics approach. An analysis of the data resulted in the description of a new species, Laurencia mediterranea using combined morphological and molecular criteria, including COI-5P and rbcL. Morphologically L. mediterranea sp. nov. was distinct from other Laurencia spp. in the type of holdfast, the colour and shape of the thallus, the presence of secondary pit connections, lenticular thickenings and ‘corps en cerise’. Moreover, a new genetic species cluster indicated a separate taxon at the species level. Our study demonstrates that genetic sequences having clear links to sample metadata and digital herbaria are indispensable for macroalgal biodiversity research. This approach could offer a solution for algal taxonomy in cases where biogeography is important and limited sequence data exist in online DNA libraries.