Molecular diversity and phylogeny of turf-forming green seaweeds (Chlorophyta) in Brazilian oceanic islands

Author(s)

Michelle Cristine dos Santos Silva

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB)
• Defense date: 2024-09-10

Examining board members

Mariana Cabral de Oliveira; Mutue Toyota Fujii; Luanda Pereira Soares; Nair Sumie Yokoya

• Advisor: Mariana Cabral de Oliveira; Franciane Maria Pellizzari

Abstract

Oceanic islands are isolated, pristine, and ecologically important environments that supply nutrients to adjacent oligotrophic waters. They are considered steppingstones for migratory species or those dispersed by currents; thus, documenting biodiversity in these locations is essential for conservation efforts, filling biogeographical gaps, and enhancing understanding of the evolution of certain species. Macroalgae are key organisms in oceanic islands, forming an important part of the trophic web, providing food and shelter for a variety of organisms. Brazil harbors four oceanic island environments: Rocas Attol and three archipelagos, Fernando de Noronha, Saint Peter and Saint Paul Archipelago (ASPSP), and Trindade and Martin Vaz. However, the diversity of macroalgae in Brazilian oceanic islands remains incompletely elucidated, primarily due to challenges in taxonomy, especially with cryptic species among turf communities. In this study, Chlorophyta (Ulvophyceae) macroalgae samples were collected during two expeditions to Trindade Island, two to ASPSP, and one to Fernando de Noronha. For species of the orders Dasycladales, Ulvales, and Bryopsidales, plastidial markers tufA and rbcL sequences were generated. For species of the order Cladophorales, nuclear ITS, LSU, and SSU sequences were generated, as plastidial markers are not suitable for this group. Molecularly detected species were also analyzed for morphology and geographical distribution. Based on the analyses, 28 Ulvophyceae species comprising the turf were confirmed. In Trindade, 20 species were listed, 13 in Fernando de Noronha, and six in ASPSP. Among the studied species, the first sequences were obtained for Dictyosphaeria ocellata, and the occurrence of Lychaete pellucidoidea in the ASPSP Archipelago was detected for the first time. Additionally, three possible new species were detected: 1. Boodleopsis sp. recorded for all three studied oceanic islands, possibly restricted to island environments; 2. Willeella sp., a small and delicate species, possibly endemic to Trindade Island; and 3. Chaetomorpha sp., also small and part of the hidden diversity of Fernando de Noronha, which, if confirmed, will be the first endemic species for this location. TufA and rbcL sequences were generated for species with few entries in the database, such as Halimeda discoidea and Parvocaulis parvolus. Additionally, the occurrence of Ulva flexuosa in Brazilian territory was molecularly confirmed. These contributions represent a reinforcement for distribution and taxonomy studies of these species. The sequencing of Ulvophyceae species from Brazilian oceanic islands is unprecedented and contributes to understanding the marine biodiversity of these insular regions, which is essential for their preservation and for biogeographical studies of the South Atlantic. (AU)

• FAPESP's process: 19/11558-9 - Molecular diversity and phylogeny of turf-forming green algae (Chlorophyta) on Brazilian oceanic islands
• Grantee: Michelle Cristine dos Santos Silva
• Support Opportunities: Scholarships in Brazil - Doctorate