Species in the genus are crustose lichens and their photobiont (the non-fungal organism) is a single-celled green alga.

The actual roles of the three types of conidia present are not thoroughly understood, but mesoconidia are likely asexual propagules based on, for example, the observation that many of the species are frequently found with only mesopycnidia and no apothecia.

It is presumed that a shift in substrate requirement from bark to wood leads to differentiation in reproduction mode and becomes a driver of speciation in Micarea microlichens.

The case of Micarea is the first observation that among lichenized fungi reproduction mode is connected to substrate requirement.

The main hypothesis behind this phenomenon is that obligate species on dead wood need to colonize new suitable substrata relatively fast and asexual reproduction is a more effective strategy for successful colonisation.