Browsing by Author "Thibaut, Thierry"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
- Multi-generation dispersal shapes the genetic structure of the canopy-forming seaweed Ericaria amentacea syn. Cystoseira amentacea in the north-western Mediterranean SeaPublication . Reynes, Lauric; Legrand, Térence; Blanfuné, Aurélie; Assis, Jorge; Thibaut, Thierry; Bottin, LorraineCanopy-forming seaweeds, especially fucoids (Fucales, Phaeophyceae), constitute marine forests in the Mediterranean Sea that deliver key ecosystem services. However, escalating human pressures in coastal areas have led to habitat fragmentation, significantly impacting the dynamics of gene flow and evolutionary trajectories. In this study, we investigated population connectivity among 43 sites with Ericaria amentacea in the northwestern Mediterranean Sea. By integrating microsatellite genotyping and biophysical modelling, we aimed to evaluate the hypothesis that population connectivity is approximated by oceanographic connectivity, rather than coastal distance. While traditional approaches to oceanographic connectivity had focused on single-generation dispersal models, we adopted a multi-generation perspective. This involves employing a biophysical model that considers gene flow through multiple stepping-stone populations across the E. amentacea distribution and over distinct generations of dispersal. Using distance-based redundancy analysis (dbRDA), we found that multi-generation dispersal significantly contributes to genetic differentiation, surpassing the influence of coastal distance. Even so, genetic differentiation remained significant among all population pairs, suggesting that gene flow may be hindered by differential selection acting against migrants and/or obscured by the effects of local genetic drift. The latter is likely, given the species' low dispersal potential and self-compatibility, both of which promote small, spatially restricted breeding units. In addition, our results emphasized that oceanographic connectivity promoted long-distance dispersal across northern Corsica and Eastern Provence over a single generation through the drifting of fertile thalli, which might have contributed to moderate differentiation between local populations. Overall, this framework highlights the value of considering multi-generation dispersal across numerous intermediate stepping-stones for informing management strategies aimed at enhancing population connectivity and safeguarding genetic diversity in seaweeds.
- Non-indigenous seaweeds in the Northeast Atlantic Ocean, the Mediterranean Sea and Macaronesia: a critical synthesis of diversity, spatial and temporal patternsPublication . van der Loos, Luna M.; Bafort, Quinten; Bosch, Samuel; Ballesteros, Enric; Bárbara, Ignacio; Berecibar, Estibaliz; Blanfuné, Aurélie; Bogaert, Kenny; Bouckenooghe, Silke; Boudouresque, Charles-François; Brodie, Juliet; Cecere, Ester; Díaz-Tapia, Pilar; Engelen, Aschwin; Gunnarson, Karl; Shabaka, Soha Hamdy; Hoffman, Razy; Husa, Vivian; Israel, Álvaro; Karremans, Mart; Knoop, Jessica; Le Gall, Line; Maggs, Christine A.; Mineur, Frédéric; Parente, Manuela; Perk, Frank; Petrocelli, Antonella; Rodríguez-Prieto, Conxi; Ruitton, Sandrine; Sansón, Marta; A Serrao, Ester; Sfriso, Adriano; Sjøtun, Kjersti; Stiger-Pouvreau, Valérie; Surget, Gwladys; Taşkin, Ergün; Thibaut, Thierry; Tsiamis, Konstantinos; Van De Weghe, Lotte; Verlaque, Marc; Viard, Frédérique; Vranken, Sofie; Leliaert, Frederik; De Clerck, OlivierEffective monitoring of non-indigenous seaweeds and combatting their effects relies on a solid confirmation of the non-indigenous status of the respective species. We critically analysed the status of presumed non-indigenous seaweed species reported from the Mediterranean Sea, the Northeast Atlantic Ocean and Macaronesia, resulting in a list of 140 species whose non-indigenous nature is undisputed. For an additional 87 species it is unclear if they are native or non-indigenous (cryptogenic species) or their identity requires confirmation (data deficient species). We discuss the factors underlying both taxonomic and biogeographic uncertainties and outline recommendations to reduce uncertainty about the non-indigenous status of seaweeds. Our dataset consisted of over 19,000 distribution records, half of which can be attributed to only five species (Sargassum muticum, Bonnemaisonia hamifera, Asparagopsis armata, Caulerpa cylindracea and Colpomenia peregrina), while 56 species (40%) are recorded no more than once or twice. In addition, our analyses revealed considerable variation in the diversity of non-indigenous species between the geographic regions. The Eastern Mediterranean Sea is home to the largest fraction of non-indigenous seaweed species, the majority of which have a Red Sea or Indo-Pacific origin and have entered the Mediterranean Sea mostly via the Suez Canal. Non-indigenous seaweeds with native ranges situated in the Northwest Pacific make up a large fraction of the total in the Western Mediterranean Sea, Lusitania and Northern Europe, followed by non-indigenous species with a presumed Australasian origin. Uncertainty remains, however, regarding the native range of a substantial fraction of non-indigenous seaweeds in the study area. In so far as analyses of first detections can serve as a proxy for the introduction rate of non-indigenous seaweeds, these do not reveal a decrease in the introduction rate, indicating that the current measures and policies are insufficient to battle the introduction and spread of non-indigenous species in the study area.