Environmental factors that drive the distribution and abundance of a threatened cyanolichen in Southern Europe: a multi-scale approach

Premise of the study: High-quality information about threatened species is required to prevent current global biodiversity losses. Lichens are important components of forest biodiversity and help to maintain ecosystem functioning. The epiphytic cyanolichen Lobarina scrobiculata is red-listed in Europe and North America, but knowledge of its ecology and distribution in Southern Europe is scarce.

Methods: We used a multispatial scale design to investigate the effects of macroclimate, forest structure, tree features, and microhabitat on the occurrence, abundance, spatial distribution, and performance of Lobarina scrobiculata in the Iberian Peninsula at plot and tree scales. Generalized linear models and mixed models were used for analysis.

Key results: We recorded ca 14000 individuals of the threatened species Lobarina scrobiculata from 22 populations in the Iberian Peninsula. Our results suggest that L. scrobiculata thrives mainly in oak forests with highly variable annual precipitation levels. At the plot scale, the L. scrobiculata abundance increased with annual precipitation and tree density (habitat quantity). At the tree scale, our models highlighted the importance of tree size and bark roughness (habitat quality) as the main drivers of species occurrence and abundance. We detected a marked spatial pattern on tree trunks, i.e., L. scrobiculata occurred preferentially on north-facing surfaces and close to the ground where humidity is higher.

Conclusions: By integrating multiscale modeling, we analyzed a unique large dataset and these results are essential for understanding the ecology of this threatened cyanolichen. There is an urgent need to preserve the forests that this species currently inhabits as well as potential colonization sites.