Multi-scale drivers of community diversity and composition across tidal heights: an example on temperate seaweed communities

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Dinard Herbarium: A Source of Information to Infer Temporal Changes in Seaweed Communities?

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Remote sensing methods for the biophysical characterization of protected areas globally: challenges and opportunities

Protected areas (PAs) are a key strategy to reverse global biodiversity declines, but they are under increasing pressure from anthropogenic activities and concomitant effects. Thus, the heterogeneous landscapes within PAs, containing a number of different habitats and ecosystem types, are in various degrees of disturbance. Characterizing habitats and ecosystems within the global protected area network requires large-scale monitoring over long time scales. This study reviews methods for the biophysical characterization of terrestrial PAs at a global scale by means of remote sensing (RS) and provides further recommendations. To this end, we first discuss the importance of taking into account the structural and functional attributes, as well as integrating a broad spectrum of variables, to account for the different ecosystem and habitat types within PAs, considering examples at local and regional scales. We then discuss potential variables, challenges and limitations of existing global environmental stratifications, as well as the biophysical characterization of PAs, and finally offer some recommendations. Computational and interoperability issues are also discussed, as well as the potential of cloud-based platforms linked to earth observations to support large-scale characterization of PAs. Using RS to characterize PAs globally is a crucial approach to help ensure sustainable development, but it requires further work before such studies are able to inform large-scale conservation actions. This study proposes 14 recommendations in order to improve existing initiatives to biophysically characterize PAs at a global scale

Etude spatio-temporelle de la biodiversité des forêts de laminaires des côtes bretonnes par une approche intégrée de génétique des populations et d'écologie des communautés

The topic of this PhD thesis was the study of biodiversity patterns and the assessment of the underlying processes within the kelp forests. The focus of this work was to characterise the variability of biodiversity over space and time at both the intra and inter specific level. Population genetic diversity of the two sister species Laminaria digitata and Laminaria hyperborea, and the specific diversity of the understory macroalgae were studied in Brittany (France) at several hierarchical levels (along a coastline of 500 km) between seasons and across the last twenty years. Results revealed that populations of L. digitata, inhabiting the lower margin of the intertidal, were less diverse and more structured than the populations of L. hyperborea, a subtidal species. Similarly, algal communities associated to L. digitata were less diverse and more structured than those associated to L. hyperborea. These observations are likely related to the higher dispersal distance of spores and gametes in the subtidal than the intertidal. Our results demonstrated the presence of mosaic biotic conditions at the scales of the Brittany coast with contrasted spatio-temporal characteristics. This variability is most certainly the main explanation of the differences observed in biodiversity patterns. Cold waters occur along the two adjacent regions of Morlaix Bay and Iroise Sea which are characterised by moderate temperature variations between seasons and across years These two regions were the less impacted by global warming compared with the other regions of Brittany studied. Here, high levels of diversity and connectivity were reported for both intra and inter specific biodiversity in the two targeted species of kelp. Conversely, St Malo Bay had the lowest level of diversity and connectivity at the genetic and specific levels for both species L. digitata and L. hyperborea. In this region, seasonal variations of temperature amplitude were the highest observed in Brittany and this trend intensified over the two decades. In South Brittany, where sea surface temperatures were the highest, biodiversity patterns varied according to the species considered (L. digitata being at its southernmost range) and the level of diversity considered. In conclusion, our results have shown the occurrence of a mosaic of environmental conditions at a scale from 10 to 250 km. This scale is often not taken into account in ecological niche models. Moreover, correlations between spatial patterns of diversity at both the genetic and specific levels (SGDC) were generally positive. Despite the strength of association, their significance varied depending on the space and the species considered.Cette thèse a pour objet l'étude des patrons de biodiversité et des processus qui la soustendent au sein d'un écosystème marin remarquable : les forêts de laminaires. L'originalité de ce travail a été de caractériser les variations spatio-temporelles de la biodiversité conjointement à deux niveaux de diversité intra et inter-spécifique. La diversité génétique des populations des deux espèces soeurs Laminaria digitata et Laminaria hyperborea, et la diversité spécifique des macroalgues vivant sous leur canopée ont été étudiées à l'échelle de la Bretagne, dans l'espace, à différents niveaux hiérarchiques (sur 500 km de côte), et dans le temps, à l'échelle des saisons et des deux dernières décennies. Les résultats obtenus révèlent que les populations de L. digitata, occupant la marge inférieure de l'intertidal, sont moins diverses et plus structurées que celles de l'espèce subtidale : L. hyperborea. De la même manière, les communautés algales en sous strate de L. digitata sont moins diverses et plus structurées que celles associées à L. hyperborea. Ces deux observations s'expliqueraient en partie par une dispersion plus importante en zone subtidale qu'en zone intertidale. Nos résultats démontrent qu'à l'échelle du littoral breton, il existe une mosaïque de conditions abiotiques avec des caractéristiques spatio-temporelles contrastées, et que cette variabilité permet d'expliquer certaines différences dans les patrons de diversité. Ainsi, les deux régions de la baie de Morlaix et de la mer d'Iroise forment " une poche d'eau froide " caractérisée par une faible amplitude des températures à la fois saisonnières et annuelles et apparaissent comme relativement peu impactées par le changement global par rapport aux autres régions étudiées. Les niveaux de diversité et de connectivité y sont forts aussi bien pour les mesures de diversités intra et inter-spécifiques et pour les deux espèces cibles. Inversement, la baie de St Malo, montre les niveaux de diversités et de connectivités génétique et spécifique les plus faibles aussi bien pour L. digitata que pour L. hyperborea alors que c'est la région étudiée qui révèle les plus fortes amplitudes saisonnières de températures des eaux de surface, cette variabilité s'accentuant nettement au cours des deux dernières décennies. Les patrons de diversités en Bretagne Sud, où les eaux sont les plus chaudes, diffèrent selon l'espèce cible (L. digitata s'y trouve en limite d'aire) et/ou le niveau de diversité considéré. En conclusion, nos résultats montrent qu'il existe une mosaïque d'environnements différents à une échelle spatiale (10 à 250 km) qui n'est souvent pas prise en compte dans les modèles de niches écologiques prédisant les changements de biodiversité. De plus, les corrélations entre les patrons spatiaux de diversité génétique et spécifique (SGDC) sont généralement positives, bien que leur force et leur significativité varient dans l'espace et/ou selon l'espèce cible considérée

Management and conservation of the kelp species

Marine protected areas (MPAs) have been depicted as a useful tool for improving fishery management and protecting biodiversity. For example, by acting as source populations, MPAs may provide a spillover of adults/propagules, enhancing recruitment to surrounding, non-protected waters. However, such positive effect will depend on how a MPAs design matches population biology and dispersal abilities of the target species. High levels of intraspecific genetic diversity without pronounced structure have been found in many marine organisms over large spatial scales (from hundreds to thousands kilometres) but do not hold for other ecologically and economically important species such as coral reef fishes, seagrasses and kelps. In particular, the limited potential for dispersal of many macroalgae suggests the occurrence of self-sustaining, “closed” populations that contrast with the “open” populations of many fishes and invertebrates. Consequently, the high resilience of fish/invertebrate populations cannot be generalized to the whole marine realm. In the present work, we use genetic tools to explore the role of the MPA Parc naturel marin d’Iroise in the management of the emblematic kelp Laminaria digitata. While kelps have received much more scientific attention than any other seaweed group, there is still critical baseline knowledge which needs to be addressed for their effective management. Our genetic survey of 12 L. digitata populations along the Brittany coast, four of them located within the boundaries of the Parc naturel marin d’Iroise, allowed us to assess the conservation value of these kelp populations. In particular, classical genetic metrics as well as more recent clustering approaches were used to identify and characterize Management Units. Moreover, assignment tests were employed to determine contemporary migration events and source/sink populations. Our results show that populations within this MPA have high conservation value. However, we also identify other populations of conservation interest

Comparaison des patrons de diversité génétique entre deux espèces soeurs de laminaires le long du littoral breton

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How does molecular-assisted identification affect our estimation of α, β and γ biodiversity? An example from understory red seaweeds (Rhodophyta) of Laminaria kelp forests in Brittany, France

International audienceUsing two distinct identification methods, one based on morphological characters only and the other combining morphological and molecular characters (integrative identification method), we investigated the differences in the biodiversity patterns of red seaweed communities associated with kelp forests at various spatial scales: the regional diversity of Brittany, France (γ-diversity), the local diversity at different Breton sites (α-diversity) and the differentiation in species diversity and abundances among those sites (β-diversity). To characterise α and β diversities, we conducted an initial survey in winter 2011 at 20 sites belonging to four different sub-regions, with specimens collected from six quadrats of 0.10 m2 at each site, three in the tidal zone dominated by Laminaria digitata and three in the zone dominated by Laminaria hyperborea. To further characterise the regional diversity, we carried out another survey combining several sampling methods (quadrats and visual census) in different seasons (winter, spring and summer) and different years (2011 and 2012). In all, we collected 1990 specimens that were assigned to 76 taxa with the identification method based on morphological characters and 139 taxa using the integrative method. For γ and α diversity, the use of molecular characters revealed several cases of cryptic diversity and both increased the number of identified taxa and improved their taxonomic resolution. However, the addition of molecular characters for specimen identification only slightly affected estimates of β-diversity

Data from: Contrasting genetic diversity patterns in two sister kelp species co-distributed along the coast of Brittany, France

We investigated patterns of genetic structure in two sister kelp species to explore how distribution width along the shore, zonation, latitudinal distribution and historical factors contribute to contrasting patterns of genetic diversity. We implemented a hierarchical sampling scheme to compare patterns of genetic diversity and structure in these two kelp species co-distributed along the coasts of Brittany (France) using a total of 12 microsatellites, 9 for Laminaria hyperborea and 11 for Laminaria digitata, of which 8 amplified in both species. The genetic diversity and connectivity of L. hyperborea populations was greater than that of L. digitata populations in accordance with the larger cross-shore distribution width along the coast and the greater depth occupied by L. hyperborea populations in contrast to L. digitata populations. In addition, marginal populations showed reduced genetic diversity and connectivity, which erased isolation-by-distance patterns in both species. As L. digitata encounters its southern range limit in southern Brittany while L. hyperborea extends down to mid-Portugal, it was possible to distinguish the effect of habitat continuity from range edge effects. We found that L. digitata did not harbour high regional diversity at its southern edge, as expected in a typical rear edge, suggesting that refuges from the last glacial maximum for L. digitata were probably not located in southern Brittany, but most likely further north. For both species, the highest levels of genetic diversity were found in the Iroise Sea and Morlaix Bay, the two regions in which they are being currently harvested. Preserving genetic diversity of these two foundation species in these areas should, thus, be a priority for the management of this resource in Brittany