Algas coralináceas incrustantes da ordem Corallinales (Corallinophycidae, Rhodophyta) no Atlântico Sul: aspectos morfológicos e moleculares

Abstract

Corallinales currently includes a single family – Corallinaceae – which presents six subfamilies: Corallinoideae, Hydrolithoideae, Lithophylloideae, Mastophoroideae, Metagoniolihoideae and Neogoniolithoideae. The reef-building crustose coralline algae are mainly represented by taxa classified in Corallinaceae. These algae produce important sedimentary deposits, increasing the habitat heterogeneity and availability of niches, which results in a greater diversity of species. The Brazilian coast is notable for having extensive reef areas. Despite the great importance of this group of algae for the resilience of biodiversity, many species of crustose coralline algae referred for the South Atlantic, as the representatives of Metagoniolithoideae and Neogoniolithoideae, need to be extensively reviewed, besides the need for revision in the light of molecular biology. The present study aimed to contribute to the knowledge of the taxonomy of non-geniculate species of Corallinales in the South Atlantic, based on morpho-anatomical and molecular studies. Sampling was carried out in 75 localities along the Brazilian coast. Taxa were described and identified based on morpho-anatomical characteristics, using optical and scanning electron microscopy observations, and molecular data based on four markers (COI-5P, psbA, rbcL-3P and SSU rDNA). Thirteen infrageneric taxa belonging to three subfamilies of Corallinaceae were identified. The subfamily Lithophylloideae was represented by three species (Lithophyllum atlanticum, L. margaritae and Lithophyllum sp.). Neogoniolithoideae was also represented by three species (Neogoniolithon cf. brassica-florida, N. rhizophorae and N. crypticum sp. nov.), including one new to Science (N. crypticum sp. nov.), and one new occurrence for the South Atlantic (N. rhizophorae). We described a new genus, Tomitolithon, classified in Metagoniolithoideae including two new species (T. deniquerum and T. polistratum); three new species were described and classified in the genus Harveylithon (H. catarinense, H. maris-bahiensis and H. riosmenum); and we also identified the species Porolithon onkodes and Pneophyllum conicum. In addition, a new circumscription of the subfamily Metagoniolithoideae was proposed. The four markers tested were effective for the delimitation of genera and species. However, the nuclear region SSU rDNA should be used with caution for species delimitation, as it is more efficient at higher levels such as orders, families and subfamilies. These results represent an important contribution to the knowledge of the diversity of this group of crustose coralline algae.