Genetic connectivity and diversity of the seagrass Halodule wrightii in contrasting habitats of the Western African coast

• Autor(a) principal: Fernandes, Gabriela de Souza
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.1/19532
• topic: Conectividade; Diversidade genética; Halodule wrightii; Costa africana ocidental; Dispersão de sementes; Recrutamento; Domínio/Área Científica::Ciências Naturais::Outras Ciências Naturais

Understanding the patterns and processes of genetic diversity and differentiation is fundamental for assessing population connectivity to inform the conservation of coastal ecosystems. The tropical West African Atlantic Coast is a good model to address these issues. The influence of oceanographic currents diverging in hotspot ecoregions mediating propagule dispersal along this coastline raises interesting predictions to be tested. In the Gulf of Arguin (Mauritania) nearshore and offshore seagrass populations can be predicted to be highly connected by strong currents driven by tides in this very shallow system. In contrast, in the Bijagós archipelago (Guinea-Bissau), populations in the northern and southern islands could hypothetically be genetically differentiated as predicted based on passive transport by ocean currents. However, they also have a strong relationship of connectivity by migratory species, namely green turtles that travel between feeding and breeding grounds. This study aims to assess these predictions and also to understand seagrass population genetic diversity and genotypic (clonal) diversity, as well as connectivity, along the Western African coast. We used as model the species Halodule wrightii, a seagrass with clonal reproduction via rhizome elongation and sexual reproduction via non-buoyant seeds, both traits that do not promote long distance dispersal. We assessed genetic diversity, clonality, and population differentiation with 8 microsatellite markers, using samples from the entire species range along this coastline, from Mauritania to Angola over a distance of ~1,600 km. Generally, populations were genetically homogeneous with low differentiation, while genotypic richness varied among all populations. The results support the hypothesis of high connectivity between populations in the Banc d’Arguin but do not support the isolation hypothesis between the northern and southern regions of the Bijagós. The results also suggest that the Canary Current and Guinea Current do not affect seed dispersal and connectivity through abiotic mechanisms.