New insights on stomata analysis of European conifers 65 years after the pioneering study of Werner Trautmann (1953)

International audienceConifer-stomata analysis is an essential part of the palaeoecological toolbox because it allows the determination of the local presence of plant populations with a lower degree of uncertainty than pollen analysis. Although the European postglacial pool of conifer taxa is broad, stomata morphologies for only few taxa have been investigated. Prior stomata morphology studies focused on taxa having wide distribution ranges in central and northern Europe, and stomata morphologies for taxa occurring in southern European and Northern African mountain regions have not yet been described. Here, we present a qualitative assessment of stomata morphologies for 40 taxa from eight genera (Cupressus, Juniperus, Abies, Cedrus, Larix, Picea, Pinus and Taxus) that are present on the European continent and the southern borderlands of the Mediterranean Basin, thereby broadening substantially both the regional and taxonomical coverage of this now 65-years old technique. We found that visual identification of conifer stomata does not allow species-level identifications, supporting the notion of genus-specific stomata morphologies found in prior studies. For each genus, we describe the stomata morphologies taking into account the varying shape of stomata features at different focusing levels. In addition, we provide stop-motion animations (publicly available at http://dx.doi.org/10.6084/m9.figshare.7165261) that may be useful tools for microscope analysts who wish to acquaint themselves with conifer-stomata analysis