[eng] Aim: The historical causes responsible for the wide distribution of terricolous, crustose lichenized fungi across the Mediterranean Basin and the Canary Islands have never been explored. Here, we used the terricolous, circum Mediterranean/Macaronesian species Buellia zoharyi (Caliciaceae, Ascomycota) to infer the time frame, and the climatic, geological and ecological factors influencing the origin and current spatial distribution of this species.
Location: Mediterranean Basin and Canary Islands.
Methods: Data from two nuclear markers (nrITS and tef1) obtained from 226 specimens of 23 populations covering the entire distribution range of B. zoharyi were used to calculate genetic diversity indices and haplotype networks and to investigate population size changes and structure. Three secondary calibrations were used to estimate the timing of the divergence of B. zoharyi from its hypothesized sister species, B. elegans, and the diversification of B. zoharyi.
Results: We found low nucleotide diversity and two geographically differentiated
haplogroups, with a contact zone in the Iberian Peninsula. The three dating
approaches established wide temporal windows for the divergence of B. zoharyi
from B. elegans (Eocene‐Pliocene) and its diversification (Miocene‐Pleistocene).
These intervals overlap with the origin and diversification ages found in other
lichen‐forming fungi and vascular plants inhabiting the Mediterranean region.
Main conclusions: In the context of lichen biogeography, our results support
ecological specialization as well as geological and climatic events as drivers of the
evolutionary history of B. zoharyi in the Mediterranean. In particular, the combined
effects of the Messinian salinity crisis and the subsequent Zanclean Flood on the
availability of gypsum soils in the Mediterranean Basin, as well as the Quaternary
climatic oscillations, seem to have collectively shaped the amount and distribution
of B. zoharyi population genetic diversity.