Sistemática e filogenia do gênero Centroceras Kützing (Ceramiaceae, Rhodophyta)

Abstract

The genus Centroceras comprises filamentous marine red algae with complete cortication of the thallus, originating from periaxial cells, which consistently divide into two acropetal and one basipetal cells. Although morphological characteristics are traditionally employed to differentiate its species, the overlapping of these traits hampers accurate delimitation within the genus. This identification challenge has led to the adoption of phylogenetic techniques, which have revealed cryptic diversity within the group. Furthermore, the genus has undergone significant nomenclatural changes, particularly following the introduction of molecular biology. The first taxonomic revision of the genus Centroceras in the post-DNA era of macroalgal taxonomy revealed that Centroceras clavulatum (Agardh) Montagne is not a single species, but rather a species complex. Currently, the genus includes 18 species, several of which have been recently recognized. This study aimed to revise and analyze the systematics of the genus Centroceras using phylogenetic tools to refine the group’s taxonomic classification. Novel sequences were generated and analyzed for the Brazilian coast, in addition to data retrieved from GenBank, using two molecular markers: rbcL and COI-5P. The results indicated a need for taxonomic reorganization within the genus Centroceras. A key finding was the identification of the C. gasparrinii (Meneghini) Kützing complex, which possibly encompasses five distinct species, and the reinstatement of C. macracanthum Kützing for the Brazilian coast. Additionally, the distribution of C. gasparrinii was confirmed in both the Mediterranean Sea and the Sea of Japan. Molecular analyses also led to the identification of a new species from the Brazilian coast, occurring in two specific locations in Bahia and Rio de Janeiro. Furthermore, the results reinforced that morphology alone does not meet the criteria required for accurate species recognition within this genus. Morphological approaches may result in species underreporting, hinder the discovery of new taxa, and lead to nomenclatural misassignments. Based on molecular data, 16 species are currently recognized at the molecular level. When morphologically based species are included, the total number reaches 23. This revision excludes the occurrence of C. micracanthum sensu Won, Cho &

Fredericq and C. gasparrinii from the Brazilian marine flora, as previously suggested by other studies. The study concludes that the integration of molecular data and phylogenetic methods, coupled with careful nomenclatural revision, allows for a more precise delimitation of Centroceras species, revealing a complex diversity and providing a more robust and up-to-date nomenclatural reorganization for the genus. In summary, this study significantly contributes to the understanding of the diversity and phylogeny of the genus Centroceras, highlighting the importance of molecular data in taxonomy and offering clearer insights into species distribution and identification, including the detection of novel species and the implementation of necessary nomenclatural adjustments.