Digenea nana sp. nov. (Rhodomelaceae, Rhodophyta), a new turf-forming, coral reef species from the Western Tropical Atlantic

Abstract

ABSTRACT The number of newly described species has increased since the addition of molecular data to taxonomic studies, revealing that species considered widely distributed by morphological and anatomical studies are often comprised of complexes of several distinct species. This study reports on a new turf-forming species of Digenea from the Greater Caribbean (South Florida and eastern Cuba), previously identified as D. simplex based on morpho-anatomical characters, but shown through DNA sequences to be a distinct species. Digenea nana sp. nov. is characterized by its small brush appearance, small dimensions (2.5 cm high and 0.6 mm wide), long determinate branches reaching 15 mm in length (its most striking feature) and 11–12 pericentral cells. Digenea nana is distinct from all its congeners, showing sequence divergences of 3.5–5.0% in COI-5P and 1.7–2.7% in rbcL. The species resolved as sister to D. rafaelii (genetic distance of about 3.5% and 1.7% in COI-5P and rbcL respectively) from Pacific Mexico, and can be easily distinguished by morpho-anatomical characters. Digenea nana is the seventh species in the genus worldwide. Given the presumed wide distribution of D. simplex, based solely on morpho-anatomy, and the number of cryptic and pseudo-cryptic species recently described, further integrative molecular and morpho-anatomical studies are likely to reveal new taxa.