A surprisingly diverse population of microscopic green algae is found in desert microbiotic crusts, with many having made the evolutionary leap from aquatic to terrestrial habitats. Here, Zoe Cardon, Magdalena Bezanilla and colleagues (Cardon, et al. 2018) present an initial characterisation of a set of closely related but differentially adapted green algal species within the family Scenedesmaceae. The three desert and two aquatic species enable study of the evolution of desiccation tolerance and determinants of multicellularity. The authors show that all five species divide by multiple (rather than binary) fission, however, the progeny of the three desert-derived species are unicellular, whereas the two aquatic-derived species form multicellular colonies. The three desert species survive repeated desiccation and rehydration, whereas the aquatic species died or recovered very little photosynthetic activity after desiccation. This contrast is mirrored by differential accumulation of intracellular reactive oxygen species in rehydrated cells. These findings indicate that these five species within the Scenedesmaceae are a promising group for the comparative analyses of green microalgal form and function.
