Hydration traits in cephalolichen members of the epiphytic old forest genusLobaria(s. lat.)

Abstract

AbstractThis study aims to quantify the size-dependency of important hydration traits inLobaria amplissima, L. pulmonariaandL. virenssampled in sympatric populations on deciduous tree trunks in southern Norway, and to discuss possible implications of species-specific traits for the ecological niches of these old forest cephalolichens. Traits measured were thallus size (area and mass), specific thallus mass (STM), internal (WHCinternal) and external water-holding capacity (WHCexternal), and water content (WC) after shaking and after blotting.Lobaria amplissimahad the highest WHCinternal, 2·6 times higher thanL. pulmonariawith the lowest WHCinternal. WHCinternal, driven by STM, strongly depended on size. WHCexternalwas 28% (L. virens)to 47% (L. pulmonaria) of the WHCinternal. Unlike WHCinternal, WHCexternaldid not depend on thallus area, meaning that WHCexternalis proportionally higher for smaller compared with larger thalli. The most widespread species,L. pulmonaria, benefits from a flexible hydration strategy due to low STM, facilitating the use of more diverse water sources than the other two species that depend more on rain, particularlyL. amplissimawith the highest STM and thus relatively high WHCinternal. ForL. virens, a combination of less specialized hydration traits and a low tolerance to higher light intensity probably jeopardizes its survival outside rainforest habitats.