New insights on the distribution and habitat of Ulvella endozoica (Ulvellaceae, Chlorophyta) in the tropical Southwestern Atlantic, based on thallus ontogeny in culture and DNA barcoding

Abstract

The small size (< 5 mm) of marine microfilamentous green algae makes it difficult to identify based on field collections, remaining largely unnoticed. To catalogue the diversity of these diminutive marine algae, a combination of culture-based taxonomic studies and DNA barcoding has proven to be a successful approach. During subtidal surveys in the northeastern Brazil, microfilamentous green algae were isolated as epiphytes on red algae cultured in laboratory. In this work, we used thallus ontogeny and plastid tufA gene sequences to elucidate the taxonomic identity of these isolates. Molecular and morphological evidence revealed that Brazilian specimens correspond to Ulvella endozoica, a poorly known species thought to be endemic to Florida, its type locality. Since U. endozoica was not found in gorgonian corals, as in the original description, this species does not follow a host specificity pattern, growing in more diverse substrata than previously thought. The origin of U. endozoica in Brazil remains undetermined, and we concluded that it is a cryptogenic species. Limited sampling, troublesome taxonomy, and difficulty in finding Ulvella species make them overlooked in Western Atlantic, resulting in taxonomic and biogeographic gaps. Our results expand southward the known distribution range of U. endozoica, demonstrating that an integrative barcode and laboratory culture-based approach is critical to uncover these inconspicuous algae.