Cryptic diversity of Bangiales (Rhodophyta) along the Italian coasts revealed by DNA barcoding

The order Bangiales (1) includes red algae exhibiting morphological similarity and anatomical simplicity, geographically ubiquitous, occurring from tropical to polar seas; most species are intertidal, growing on rocks, shells, or other algae, but some are found solely in subtidal habitats, and some are obligate epiphytes (2). A single family, Bangiaceae (3), is defined within the order of Bangiales, traditionallyincluding two basing on the gametophyte morphology: species with filamentous gametophyte have been included in the genus Bangia Lyngbye (4), while species with laminar gametophyte in the genus Porphyra C.Agardh (5). According to Yoon et al. (6) and most previous authors, Bangiaceae include twelve genera with ca. 130 species. Instead, a comprehensive revision of the order of Bangiales (2) recognized fifteen genera, seven filamentous and eight foliose, and three further lineages including filamentous entities still to be defined nomenclaturally. Due to their simple and highly variable morphology, one of the major challenges for taxonomy of the Bangiales is the difficulty in identifying taxa based solely on morphological and anatomical characteristics (7). A comprehensive review of the taxonomic status of Bangiales in the Mediterranean basin has not completed yet (8, 9, 10, 11, 12). The aim of the present paper is to report on a DNA barcoding survey of Bangiales along Italian coasts. Sampling of representative of the Bangiales was conducted in various localities along Italian coasts. Collected specimens were pressed onto herbarium sheets (hold at PhL and PC) and subsamples were dehydrated in silica gel for subsequent molecular analyses. The specimens have been sequenced for the DNA barcode gene (COI5’) and obtained sequences were contrasted to public online databases (BOLD, GenBank) (13, 14). Furthermore, an alignment including also all publicly available COI5’ sequences of Bangiales was built and a distance tree generated. Among specimens identified in the field basing on morphological features as Pyropia leucosticta, DNA barcodes showed the presence of P. yezoensis, P. koreana, and P. elongata. DNA barcoding data obtained from collected specimens of Bangia s.l. suggested the presence of three cryptic species, two of which already reported in north Atlantic. The need of comparison with type and historical specimens, the verification of old names and, last but not least, the definition of diagnostic characters for such taxa prove to be a challenge.