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Trees play a key role in the structure and function of many ecosystems worldwide. In the Mediterranean Basin, forests cover approximately 22% of the total land area hosting a large number of endemics (46 species). Despite its particularities and vulnerability, the biodiversity of Mediterranean trees is not well known at the taxonomic, spatial, functional, and genetic levels required for conservation applications. The WOODIV database fills this gap by providing reliable occurrences, four functional traits (plant height, seed mass, wood density, and specific leaf area), and sequences from three DNA-regions (rbcL, matK, and trnH-psbA), together with modelled occurrences and a phylogeny for all 210 Euro-Mediterranean tree species. We compiled, homogenized, and verified occurrence data from sparse datasets and collated them on an INSPIRE-compliant 10 × 10 km grid. We also gathered functional trait and genetic data, filling existing gaps where possible. The WOODIV database can benefit macroecological studies in the fields of conservation, biogeography, and community ecology.

Environmental DNA (eDNA) metabarcoding has recently gain much attention to assess aquatic environment biodiversity. A great variety of protocols have been developed to collect, extract, and analyze eDNA, some of which are continuously evolving and optimized with technological improvements. Such technological shifts might deprecate the biological data produced with earlier protocols, leading to a loss of biological knowledge. Here, we investigated the robustness of an aquatic eDNA metabarcoding method through the comparison of two biodiversity datasets generated by two optimized protocols with different collection and extraction steps. To this end, we compared fish community richness and composition of 12 streams and 3 rivers from French Guiana, sampled with two distinct protocols commonly used in aquatic eDNA studies. Although sample collection with each protocol was not achieved the same year, our results show that species richness and species composition were only slightly affected by the protocol choice, both protocols producing similar fish assemblages at each sample site. Both protocols had a higher replicability in streams than in rivers, strengthening the importance to adapt sampling effort to waterbody type as rivers host a larger number of species than small streams. Despite the need for a standardized approach in eDNA metabarcoding studies, testing the robustness of datasets to protocol variations remains crucial to valorize old data, time series, or data collected in difficult to access locations.

International audience; The statistical reliability of a pollen count in representing the true composition of modern and fossil pollen assemblages depends on the minimum number of pollen grains counted. In palynological literature this number varies between b150 and N1000, but very few studies have probed the question using robust statistical approaches. Here, we use the Pearson-Brown Prophecy formula and apply it to different fossil pollen counts from two large lake systems in Iran to calculate the minimum terrestrial and total pollen count necessary to obtain a reliable representativity of pollen assemblages. Our results surprisingly show that a pollen count of b150 is sufficient to achieve a reliability of 0.90 with no additional significant information obtained when counting more pollen. If the upland vegetation reconstruction is important, then terrestrial pollen counts as low as 67 could be sufficient. It seems that the statistically significant pollen counts are site-specific and vary between different environments and even within the same type of environment. We suggest that this value should be calculated for each pollen site so that the pollen analysts can more efficiently manage their time when counting pollen slides.