A virtual reference herbarium for the ubiquitous lichen genus Cladonia

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Lichens are important components of our ecosystems and, as indicator organisms, are regularly used for monitoring the ecological status of habitats. However, knowledge on their distribution is still sparse, because they are rather inconspicuous and difficult to identify. The identification of unknown species regularly requires comparison with reference material, even for specialists. We suggest here to generate a digital reference herbarium for a ubiquitous and common group of lichens to aid specialists and citizen scientists in the identification of taxa.The genus Cladonia is a perfect starting point for such a project. Its species are cosmopolitan colonizers of soil, plant detritus and wood, and of high conservation concern. In addition, they are the lichens most frequently collected by non-experts. Their identification is difficult, because most species are extremely variable and interspecific differences are subtle. Starting with the unique Cladonia collection of Ludwig Scriba (1847-1933) in FR, rich in types and exsiccatae, we want to create a digital reference herbarium reflecting the full variability of the genus to support the wider scientific community in the reliable identification of Cladonia.In a new approach involving z-stacking and x-y tiling of high-resolution microscopic images we want to digitize ca. 8.000 whole voucher specimens allowing users to study consistently sharp images even of large herbarium specimens online. Additional information on chemical characters will allow specialists to revise vouchers online. All images will be permanently available through Senckenberg’s collection data base SeSam and accessible through several international web portals.