Adaptations of epilithic lichens to the microclimate conditions of the White Sea coast

Abstract

Anatomical and functional features of the following three epilithic lichens Umbilicaria torrefacta, Physcia caesia, Physcia dubia were studied. These species have different morphological characteristics of thalli and occupy similar environmental conditions on supralittoral of the White Sea coast. The studied lichens are widespread in the territory of Karelia. U. torrefacta is an obligate epilithic species, Physcia caesia and Physcia dubia colonize both bark of trees and stones. Within the study area, these species were found only on coastal boulders. Photobiont of all studied lichens is unicellular green alga of the genus Trebouxia (Purvis et al. 1992). Based on the study, it was found that Ph. caesia adapts to the environmental conditions through the variability of photosynthetic pigments level which is confirmed by a strong variation of the chlorophylls a/b ratio and chlorophylls/carotenoids ratio (coefficient of variation, CV > 42%) with the stability of anatomical structures (CV ≤ 11%) – functional adaptation. Lichen Ph. dubia adapts through the variability of anatomical layers (upper cortex, algal layer, medullae, lower cortex, thallus thickness) (CV > 22%), and amounts of photosynthetic pigments (CV > 19%) – structural and functional adaptation. For U. torrefacta, the structural adaptation to environmental conditions (CV thickness of anatomical layers > 28%, CV amounts of photosynthetic pigments – 7, 8%) was recorded.