Biological soil crusts as unique microecosystem represent a suitable model system to address taxonomy and cryptic diversity of microalgal key players
On a global scale, biological soil crusts (BSC) are the most productive microbial biomass in arid and other extreme regions with various microalgal taxa as key components. BSCs are formed by different living organisms and their by-products, creating a microecosystem with microalgae as key players. The systematics of microalgae is currently changing from a morphological to a molecular phylogenetic species concept. Both systems disagree in taxonomical classification and species delimitation – a fundamental problem for accurate biodiversity estimation that needs to be addressed.
For example, the ubiquitous algae Stichococcus is known from BSCs from various, world-wide habitats, e.g. Arctic, sandy dunes and former mining sites. The world-wide distribution of BSCs makes this interesting microhabitat a suitable candidate to observe speciation processes in microalgae along geographical gradients and varying environmental stressors.
Also, the biodiversity of Bacillariophyceae (diatoms) is surprisingly high in BSCs – not only many different frustules were observed but also living representatives of terrestrial diatoms. Morphological identification of the pennate frustules was sometimes not possible, maybe because of missing information. Terrestrial diatoms are subject of research since decades, but only few studies were published so far. We would like to describe the diatoms biodiversity within biological soil crusts with focus on yet unknown species or even genera.
A polyphasic approach based on molecular data analyzed by modern algorithms and supported by morphological and ecophysiological characteristics will result in a robust taxonomy as well as in the discovery and definition of new species.