The ecology of the lichen genus Xanthoparmelia in Italy: An investigation throughout spatial scales

Abstract

This article investigates the ecological requirements driving the overlapping of species distributions within the lichen genus Xanthoparmelia in Italy. In particular, we explored the ecological requirements of chemically and morphologically similar taxa, including four species pairs with sexual vs. vegetative reproduction (Xanthoparmelia loxodes–Xanthoparmelia delisei; Xanthoparmelia angustiphylla–Xanthoparmelia conspersa; Xanthoparmelia cumberlandia–Xanthoparmelia plittii; Xanthoparmelia mexicana–Xanthoparmelia sublaevis) and five morphologically related taxa with different chemosyndromes (Xanthoparmelia stenophylla–Xanthoparmelia protomatrae; Xanthoparmelia pulla–Xanthoparmelia perrugata–Xanthoparmelia luteonotata). Basing our analysis on three different spatial scales (transect, outcrop, national), we investigated the co-occurrence of the species along gradients of micro- and macro-environmental factors. Cluster analysis and information theory measures were used to estimate the relative importance of ecological predictors of species occurrence. Three main distributional trends of pairs and chemospecies were recognized, ranging from the co-occurrence only at local level to a continuous overlapping throughout the three spatial scales of observation. Substrata mineral composition (especially rock calcium content) and climatic features (mainly related to atmospheric humidity) were the most relevant factors driving species pair distribution, at both national and local scales.