Lichenization is a symbiotic ecological strategy that is widely distributed among the fungi, but in which the diversity of partners is relatively poorly known. Limited morphological diversity has hindered the recognition of true diversity in many lichen fungi, and also in their algal partners. In the temperate and boreal zones, the crustose microlichens are the most speciose but arguably the least studied, particularly in terms of their photobiont partners. In this study, we sampled eight species of Micarea s. str. collected from Europe, culturing and sequencing their green-algal partners using chloroplast (rbcL) and nuclear ribosomal (nucSSU) markers. All specimens collected in Great Britain were associated with members of Coccomyxa (including Pseudococcomyxa), but in the smaller sample of Ukrainian material, both Coccomyxa and Elliptochloris were found. This study extends the known range of fungal hosts for symbionts in the genus Coccomyxa, and supports earlier findings that a separate lineage of predominantly non-symbiotic Coccomyxa exists.
