Browsing by Author "Viard, Frédérique"
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- A genome-wide investigation of the worldwide invader Sargassum muticum shows high success albeit (almost) no genetic diversityPublication . Le Cam, Sabrina; Daguin-Thiebaut, Claire; Bouchemousse, Sarah; Engelen, Aschwin; Mieszkowska, Nova; Viard, FrédériqueTwenty years of genetic studies of marine invaders have shown that successful invaders are often characterized by native and introduced populations displaying similar levels of genetic diversity. This pattern is presumably due to high propagule pressure and repeated introductions. The opposite pattern is reported in this study of the brown seaweed, Sargassum muticum, an emblematic species for circumglobal invasions. Albeit demonstrating polymorphism in the native range, microsatellites failed to detect any genetic variation over 1,269 individuals sampled from 46 locations over the Pacific-Atlantic introduction range. Single-nucleotide polymorphisms (SNPs) obtained from ddRAD sequencing revealed some genetic variation, but confirmed severe founder events in both the Pacific and Atlantic introduction ranges. Our study thus exemplifies the need for extreme caution in interpreting neutral genetic diversity as a proxy for invasive potential. Our results confirm a previously hypothesized transoceanic secondary introduction from NE Pacific to Europe. However, the SNP panel unexpectedly revealed two additional distinct genetic origins of introductions. Also, conversely to scenarios based on historical records, southern rather than northern NE Pacific populations could have seeded most of the European populations. Finally, the most recently introduced populations showed the lowest selfing rates, suggesting higher levels of recombination might be beneficial at the early stage of the introduction process (i.e., facilitating evolutionary novelties), whereas uniparental reproduction might be favored later in sustainably established populations (i.e., sustaining local adaptation).
- Integrating reproductive phenology in ecological niche models changed the predicted future ranges of a marine invaderPublication . Chefaoui, Rosa; Serebryakova, Alexandra; Engelen, Aschwin; Viard, Frédérique; Serrao, EsterAim Phenology of a wide diversity of organisms has a dependency on climate, usually with reproductive periods beginning earlier in the year and lasting longer at lower latitudes. Temperature and day length are known environmental drivers of the reproductive timing of many species. Hence, reproductive phenology is sensitive to warming and is important to be considered for reliable predictions of species distributions. This is particularly relevant for rapidly spreading non-indigenous species (NIS). In this study, we forecast the future ranges of a NIS, the seaweed Sargassum muticum, including its reproductive phenology. Location Coastal areas of the Northern Hemisphere (Pacific and Atlantic oceans). Methods We used ecological niche modelling to predict the distribution of S. muticum under two scenarios forecasting limited (RCP 2.6) and severe (RCP 8.5) future climate changes. We then refined our predictions with a hybrid model using sea surface temperature constraints on reproductive phenology. Results Under the most severe climate change scenario, we predicted northward expansions which may have significant ecological consequences for subarctic coastal ecosystems. However, in lower latitudes, habitats currently occupied by S. muticum will no longer be suitable, creating opportunities for substantial community changes. The temperature constraints imposed by the reproductive window were shown to restrict the modelled future species expansion strongly. Under the RCP 8.5 scenario, the total range area was expected to increase by 61.75% by 2100, but only by 1.63% when the reproductive temperature window was considered. Main conclusions Altogether these results exemplify the need to integrate phenology better to improve the prediction of future distributional shifts at local and regional scales.
- 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.
- Summer shifts of bacterial communities associated with the invasive brown seaweed Sargassum muticum are location and tissue dependentPublication . Serebryakova, Alexandra; Aires, Tânia; Viard, Frédérique; Serrao, Ester; Engelen, AschwinSeaweed-associated microbiota experience spatial and temporal shifts in response to changing environmental conditions and seaweed physiology. These shifts may result in structural, functional and behavioral changes in the host with potential consequences for its fitness. They, thus, may help the host to adapt to changing environmental conditions. The current knowledge of seasonal variation of seaweed-associated microbiota is however still limited. In this study, we explored temporal and spatial variation of microbial communities associated with the invasive brown seaweed S. muticum. We sampled in northern and southern Portugal, in September, March and July-August (summer). In addition, as (pseudo-)perennial seaweeds display seasonal reproductive phenology, we sampled various parts of the individuals to disentangle the effect of temporal changes from those due to structural development variations. The diversity and structure of associated microbial communities were determined using next generation sequencing of the variable regions V5-7 of the 16S rDNA. We expected to find differentiation in associated microbial communities between regions and sampling months, but with differences depending on the seaweed structure examined. As expected, the study revealed substantial temporal shifts in S. muticum microbiome, for instance with large abundance of Rhodobacteraceae and Loktanella in September-March but prevalence of Pirellulales during the summer months. Variations between regions and tissues were also observed: in northern Portugal and on basal structures, bacterial diversity was higher as compared to the South and apical parts. All examined seaweed structures showed temporal differences in associated microbial community structure over time, except for holdfasts between September and March. Bacteria contributing to these changes varied spatially. Conversely to all other structures, the holdfast also did not show differences in associated community structure between southern and northern regions. Our study highlights the importance of structural microscale differentiations within seaweeds hosts with regard to their associated microbial communities and their importance across temporal and spatial dimensions.