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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; Sedimentological (dry density, micro-fa-cies analysis on thin-slides, X-ray diffraction, layer counting) and elemental analyses (X-ray fluorescence) of a 3.5-m-long sediment core (MAH-B) from saline Lake Maharlou (SW Iran) were used to infer hydrological changes over the last * 3800 years. The sediment consists of thin, alternating beds of evapor-ites (halite, gypsum), carbonates (calcite, aragonite) and detrital minerals (quartz, muscovite, chlorite). We interpret the data with respect to three main hydrologic conditions: (1) nearly complete desiccation of the lake, marked by frequent halite layers, (2) hypersaline conditions marked by gypsum abundance, (3) wet conditions, characterized by high river-borne terrige-nous sediment input with high potassium content. Distinct flood layers indicate fluvial activity. From about 3800-2000 cal year BP, terrigenous sediment supply was high, with peaks at 3700-3650, 3500-3450, and 3400-3250 cal year BP. Evaporative conditions were not common. From ca. 2000 cal year BP to present, detrital minerals are less abundant, and the increase in gypsum abundance suggests drier climate with enhanced evaporation. Frequent desiccation events occurred from 1100 to 700 cal year BP. The late Holocene hydrology of Lake Maharlou corresponds well with records of dune formation and phases of river alluviation in Iran and the Arabian Peninsula, and with regional speleothem records. In addition to the influence of climate change on the lake hydrology, ancient humans modified water drainage in the catchment. Periods of subterranean tunnel (qanats) use correspond to dramatic shrinkage of the water body. We propose that climate changes drove long-term water shortages that were enhanced by anthro-pogenic activities, leading to more frequent desiccation of the lake during the last millennium.