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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

Abstract : 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.
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Submitted on : Thursday, April 10, 2014 - 4:24:34 PM
Last modification on : Wednesday, September 28, 2022 - 4:20:11 PM
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  • HAL Id : tel-00968426, version 1


Marine Robuchon. 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. Biodiversité et Ecologie. Museum national d'histoire naturelle - MNHN PARIS, 2014. Français. ⟨tel-00968426⟩



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