Lichen fecundity on the Precambrian Shield: an alternative life history strategy approach

Abstract

Symbiotic interactions are widespread in nature, but the relationship between life history, fecundity, and habitat specificity has been underexplored. This study investigated the life history strategies of foliose saxicolous lichens relative to their surrounding communities. Macrolichens were collected from 39 transects in Manitoba and Ontario. Frequency and percentage of ground cover of macrolichens, environmental variables, and numbers of apothecia and ascospores were recorded. Lichen assemblages were characterized using species similarity in a cluster analysis and ordination methods and were defined into communities using analysis of variance of the biotic variables among assemblages. Lichen life history strategies were inferred from community features, lichen fecundity, and morphological features. The general linear model determined which environmental variables may have influenced fecundity. The 81 species of macrolichens present in three lichen communities differed in species richness, with low species richness in the open mossy rock community, moderate in the grassy rock community, and high in the treed rock community. Three foliose saxicolous lichens dominated particular communities, and the life history strategy was characterized as competitive for Arctoparmelia centrifuga (L.) Hale, stress tolerant for Xanthoparmelia viriduloumbrina (Gyel.) Lendemer, and ruderal generalist for Xanthoparmelia cumberlandia (Gyel.) Hale. The proportion of sexual and asexual reproductive propagules for macrolichens showed uniformity between communities despite a significant difference in species richness. The study provides insights into the ecology of saxicolous lichens growing in the boreal forest and a characterization of lichen communities, and it shows how morphologically similar lichens can exhibit different life history strategies.