Lichen speciation is sparked by a substrate requirement shift and reproduction mode differentiation

We show that obligate lignicoles in lichenized Micarea are predominately
asexual whereas most facultative lignicoles reproduce sexually.AQ1 Our
phylogenetic analyses (ITS, mtSSU, Mcm7) together with ancestral state
reconstruction show that the shift in reproduction mode has evolved
independently several times within the group and that facultative and
obligate lignicoles are sister species. The analyses support the
assumption that the ancestor of these species was a facultative lignicole.
We hypothezise that a shift in substrate requirement from bark to wood
leads to differentiation in reproduction mode and becomes a driver of
speciation. This is the first example of lichenized fungi where
reproduction mode is connected to substrate requirement. This is also the
first example where such an association is demonstrated to spark lichen
speciation. Our main hypothesis is that obligate species on dead wood need
to colonize new suitable substrata relatively fast and asexual
reproduction is more effective a strategy for successful colonization.