SUMMARY1. Reliable assessments of groundwater biodiversity are urgently needed to resolve current issues relating to the protection of aquifers. The assessment of groundwater biodiversity is hampered by the physical complexity and difficult access to the subterranean environment, which is related to the vastness, high degree of fragmentation and environmental heterogeneity of groundwater systems. Knowledge on groundwater biodiversity is also biased towards penetrable karstic habitats (caves), whereas other common habitats such as those found in porous aquifers have been neglected. This situation calls for a standardised and comprehensive strategy to sample an exhaustive and balanced set of groundwater habitats. 2. A standardised sampling protocol aimed at capturing the main sources of environmental heterogeneity within regions was applied in six regions across Europe. Four hierarchical levels were considered: (i) region (c. 400 km 2 ); (ii) basin (c. 100 km 2 ); (iii) aquifer type (karstic or porous) and (iv) habitat (hyporheic and phreatic zones for porous aquifers; saturated and unsaturated zones for karst aquifers). A total of 192 sampling sites equally distributed among habitats were sampled within each region. 3. Stygobiotic species richness significantly varied across regions, probably as a result of important difference in physical and biogeographical characteristics among the regions. Only one species (Graeteriella unisetigera) occurred in all six regions, underlining the narrow geographic range and high degree of endemism of stygobiotic fauna. The low frequency of occurrence of stygobionts also points to the importance of rarity in ground waters and its relevance for drawing up sampling designs. 4. Rarefaction curves were calculated to determine sampling efficiencies within each region. Despite the high sampling effort, the curves did not reach saturation, especially in the Cantabria, Lessinia and Krim regions, which had the greatest numbers of rare species. 5. Species accumulation curves were also calculated by considering the main sources of environmental heterogeneity among basins, aquifer types and habitats captured by the sampling protocol. In two regions (Roussillon and Jura) sampling efficiency was improved
The interstitial subterranean isopod Microcharon (Crustacea) is highly diversified within the Mediterranean. The present distribution of 70 species is considered the result of the joint history of this genus and its environment. This stygobiont is derived from marine surface ancestors. Both Plate Tectonics and the two-step model of colonization and evolution, the second phase of which represents vicariance during the Tethys regressions, enable an understanding of the evolutionary history of this monophyletic group. The single extant marine littoral species was separated from its sister group by the closure of the Gibraltar Straits during the Messinian. The drift of the Apulian plate, the AlboranKabylian-Calabrian fragment as well as the opening of the western Mediterranean through the translation of the Corsican-Sardinia plate could explain the divergences in the western and the eastern Mediterranean. The primitive sister groups in Morocco and in Spain would have been left by the Turonian Tethys regression. Such regressions of the Tethys embayments could have played a major role in the evolution of the genus from Turonian up to Tortonian in Norht Africa, and up to Pliocene and even to Pleistocene in Italian, Iberian and Greek zones. Several eastern European species may be a product of the Paratethys regressions. Everywhere, species with plesiomorphic characters are related to old regressions and vice versa. Local geological events could have resulted in further vicariance divergences. There is a good congruence between the evolutionary history of Microcharon and other stygobiont isopod, amphipods or syncarids living in the same regions studied in the Mediterranean.
De nombreuses données existent sur la faune aquatique souterraine de France mais elles sont encore dispersées. Depuis 2002, un effort a été entrepris pour rassembler sous la forme d'une base de données, les informations disponibles concernant la distribution de cette faune aquatique souterraine de France. Un premier bilan en est présenté dans cet article. La base comprend actuellement 381 espèces et sous-espèces correspondant à plus de 5700 enregistrements. Cette diversité place la faune française parmi l'une des plus riches faunes aquatiques souterraines d'Europe. Le bilan réalisé montre que l'état actuel des connaissances est très hétérogène en fonction du groupe zoologique considéré et de la région étudiée. La base de données sera utilisée pour identifier les régions à forte de biodiversité (richesse spécifique, endémisme) et les aires françaises de conservation prioritaires. Elle permettra également de formuler et de tester différentes hypothèses sur l'origine et les facteurs responsables de la biodiversité aquatique souterraine.
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