High Host Preferences in Epiphytic Lichens Across Diverse Phorophyte Species in the Mediterranean Region

Contrary to the assumption that epiphytic lichens, which obtain water and nutrients from the atmosphere, do not exhibit host species preference, this notion is challenged by the limited number of studies that cover a wide geographical range and diverse phorophyte species (hereafter referred to as "host species"). To investigate this assumption, we evaluated the host preference of 709 epiphytic lichen species across the Mediterranean basin, examining 72 host species. The research is based on field studies conducted by the authors, supplemented with bibliographic records to expand the study area and the number of host species. We define "host preference" as the association of an epiphytic lichen species with a single host species. Our findings reveal a high prevalence of lichens exhibiting host preference both locally (exceeding 30% of lichen species in each of six geographic areas) and regionally (25% across the entire dataset). This host preference remained consistent even with increased sampling extent, which can be attributed to factors such as hosts with diverse bark types, the wide climatic range of some species, and host species associated with extreme environmental conditions within the Mediterranean region. Overall, we conclude that host bias for epiphytic lichen species remains consistent in Mediterranean landscapes, contributing to a diverse array of epiphytic species and high levels of host species preference. This research provides valuable insights into the complex interactions between lichens and their host species, offering a deeper understanding of biodiversity within Mediterranean landscapes.