Regional gradients in occurrence and size of the epiphytic lichen: Hypogymnia physodes (L.) Nyl. in southern Sweden
(English)Manuscript (preprint) (Other academic)
Background: Despite their omnipresence throughout the world, the demography of lichens is poorly documented and understood. Contributing to this lack of understanding are the small propagules involved, the difficulty of separating individuals and asexual reproduction strategies.
Aim: In the present study we searched for possible regional gradients in thallus size distribution and abundance of the common epiphytic lichen Hypogymnia physodes. We expected the species to display large-scale spatial gradients as it had been previously shown to decrease in presence in the southernmost part of Sweden. More specifically the aim was to examine whether the gradients in occurrence and diameter of thallus correspond.
Methods: The lichen was sampled on 66 sites in southern Sweden. Initial analyses were done by rotating the reference system of investigated sites around the origin to search for the angle that would result in the largest explanatory power of models fitted to data. Two models were used: one based on presence/absence data and the other on the diameter of the thalli.
Results: Presence/absence data showed an increased occurrence of H. physodes with the strongest directional gradient at 15° (north-north-east) and an increase of thallus diameter with the strongest directional gradient at 304° (west-north-west).
Conclusions: As the gradients identified in thallus size and occurrence were almost perpendicular, it seems that the processes governing growth and establishment/death do not co vary.
Diameter, direction, dispersal, distribution, forest, Hypogymnia physodes, lichen, regional gradient, thallus, tree
IdentifiersURN: urn:nbn:se:liu:diva-56491OAI: oai:DiVA.org:liu-56491DiVA: diva2:319774