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International audience; Palaeoecology is increasingly contributing to conservation biology and restoration ecology by extending the recent annual to decennial records of ecological observations to centennial and millennial time scales. One of the almost neglected potential applications of palaeoecological investigations in conservation biology is the discovering of hidden species in subrecent fossil records. Such discoveries can be common in biodiversity hotspots in which the fauna and flora are not still fully known. In this study, we present the case of the liverwort Riella in continental southwest Asia (Iranian plateau), a very vulnerable taxon growing and reproducing under very special ecological circumstances. Our study adds two new species of Riella (R. echinata and R. helicophylla) in addition to the formerly reported R. cossoniana, to the subfossil bryophyte flora of Iran. We demonstrate the important contribution that the genus has played in the history of wetland flora of the semi-arid to arid areas of Iran during the late Quaternary. We further demonstrate the possibility that it is still thriving in many wetland systems and may need to be discovered and then protected in its potential habitats. We suggest that in the biodiversity hotspots of lower latitudes, more attention has to be paid to taxonomic identification of species to reveal the hidden part of the biodiversity for defining better conservation strategies for vulnerable aquatic ecosystems such as the seasonal wetland systems.

International audience; Palynological and geochemical analyses provide valuable information about modern and past climatic regimes and vegetation. The impact of climate and humans on past vegetation in the semi-arid areas of northwestern Iran has received increased interest in the wake of warming temperatures in the Middle East. Palynological and down-core XRF elemental abundances from a peat core from Lake Neor enabled a reconstruction of vegetational changes of the past 7000 years over the highlands of northwestern Iran. Periods of increased arboreal pollen (AP) types and high (Artemisia + Poaceae)/Chenopodiaceae ratios along with low titanium abundances, high percentages of total organic carbon, more negative δD values, and higher carbon accumulation rates suggest a relatively wet climate. These conditions have persisted during the periods 6700-6200, 5200-4450 and 3200-2200 cal a BP. The overall low AP values, substantial rise of Chenopodiaceae, high Ti abundances and low values of palaeo-redox proxies, are all evidences of a drier climate, as has been reconstructed for the periods 6200-5200 and 4030-3150 cal a BP and the last 2200 years. An important feature of the last centuries is the increase of anthropogenic and pastoral indicator pollen types. Our results may provide basic data to predict future trends in vegetation dynamics under future climate change in western Asia.

International audience; Palustrine carbonates are frequently found with active and dried karstic springs in the foothills of the mountains bordering the Persepolis Basin, southwest Iran. A combination of geological conditions favours their formation, including (i) the presence of karstic limestone aquifers in the limbs of anticlines cut through by fault systems; (ii) very gentle slopes from the spring resurgence point towards the centre of the alluvial plain, creating a flat waterlogged area; and (iii) a semiarid climate with marked precipitation seasonality or significant fluctuations in water discharge and wetland water table. We suggest the term "anastomosing wetlands" or "anastomosing palustrine environments" to denote the studied karstic spring-fed carbonate wetlands, because of similarities with anastomosing river systems in aerial view. The common presence of extended anasto-mosing wetland carbonates in the Persepolis Basin and adjacent basins in the central and southern Zagros suggests that they can play an important role in the geological records of collision-related basin-and-range settings dominated by karstic limestones. Karstic spring wetlands are a main source of fresh water hosting a rich biodiversity, which attracts human communities, whose impact is visible in the archaeological material imbedded in the wetland stratigraphy. Fresh water availability, through these spring wetlands, partly explains why the semiarid Persepolis region was selected by successive civilizations, from Elamites to Persians until early Islamic entities, to establish regional centres throughout the period from the third millennium B.C. to the first millennium A.D. Only a few of these ecosystems have survived the intensive human activities of recent decades.; Des carbonates palustres sont fréquemment associés à des sources karstiques actives et asséchées dans le contrefort des montagnes bordant le bassin de Persépolis, dans le sud-ouest de l'Iran. Une combinaison de conditions géologiques favorise leur formation, à savoir : i) la présence d'aquifères de calcaires karstiques dans les flans d'anticlinaux découpés par des systèmes de failles, ii) les pentes très douces des points de résurgence de sources vers le centre de la plaine alluviale, créant une zone plane saturée et iii) un climat semi-aride caractérisé par une saisonnalité marquée des précipitations ou d'importantes fluctuations de l'écoulement de l'eau et de la nappe phréatique dans les zones humides. Nous proposons le terme « zones humides anastomosées » ou « milieux palustres anastomosés » pour désigner les zones humides à carbonates karstiques alimentées par des sources en raison de similitudes qu'elles présentent en vue aérienne avec des réseaux hydrographiques anastomosés. La présence répandue de carbonates dans les zones humides anastomosées du bassin de Persépolis et des bassins voisins des parties centrales et sud des monts Zagros indiquerait qu'ils peuvent jouer un rôle important dans les profils géologiques des milieux de bassins et montagnes. Ces milieux sont associés à des collisions tectoniques dans lesquels prédominent des calcaires karstiques. Les zones humides karstiques alimentées par des sources constituent une source d'eau douce majeure abritant une grande diversité). biologique qui attire les collectivités humaines, dont l'impact est visible dans le matériel archéologique présent dans la stratigraphie des zones humides. La disponibilité d'eau douce qu'offrent ces zones humides alimentées par des sources explique en partie pourquoi la région semi-aride de Persépolis a été retenue par des civilisations successives, des Élamites aux Perses jusqu'aux premières entités islamiques, pour y établir des centres régionaux durant toute la période allant du 3 e millénaire avant notre ère au 1er millénaire de notre ère. Seuls quelques-uns de ces écosystèmes ont survécu à l'intense activité humaine des récentes décennies.