Ulva L. biodiversity in the central Mediterranean Sea: cryptic species and new records

Ulva L. species are problematic to identify since they have cryptic morphologies with few distinctive features, as well as significant intraspecific variation. In this study, we report two new records for the Maltese islands: the heterokont benthic multicellular algae Ulva torta (Mertens) Trevisan and Ulva californica Wille, which were isolated and grown in culture from incubated natural substrata. This study includes an integrative systematics approach using both morphology and barcode sequencing of the nuclear internal transcribed spacer (ITS) region (ITS1-5.8S-ITS2), the chloroplast RUBISCO LSU (rbcL) gene and the elongation factor Tu (tufA). Subsequent phylogenetic analyses, supported the separation of these two species from other closely-related congeners that have previously been reported from the Maltese islands.