Fungal-algal interactions inRamalina menziesiiand its associated epiphytic lichen community

Abstract

Lichens are a fascinating example of a symbiotic mutualism. It is still uncertain which processes guide fungal-photobiont interactions, and whether they are random or of a more complex nature. Here, the fungal-algal interactions in Ramalina menziesii and co-occurring taxa are analyzed by using DNA sequences of the algal Internal Transcribed Spacer region (ITS), to investigate fungalalgal associations in juvenile R. menziesii and allied species. Algal species were identified by a combination of BLAST searches, median-joining network analysis, and Bayesian phylogenetics. Fungalalgal networks were analyzed for nestedness, both at the species and haplotype level (fungal species vs. algal haplotypes), and the networks were inspected for evidence of compartmentalization. Bayesian phylogenetic trees indicated that the widespread green alga Trebouxia decolorans associated with R. menziesii, as well as six other fungal species. Four additional fungal species interacted with four different species of Trebouxia. Only in one out of ten samples were algal haplotypes shared with the nearest neighbours of juvenile R. menziesii. Fungal-algal species interactions were compartmentalized, while at the level of algal haplotypes, nestedness was found. This pattern is similar to the compartmentalization found in other intimately interacting mutualists.

Ecological specialization in Trebouxia (Trebouxiophyceae) photobionts of Ramalina menziesii (Ramalinaceae) across six range‐covering ecoregions of western North America

“…The lichen disperses mainly sexually on a local scale ( Werth and Sork, 2008 ). The photobiont has been previously determined as Trebouxia decolorans Ahmadjan based on samples from southern California Sork, 2008 , 2010 ;Werth, 2012 ). Trebouxia decolorans is a common photobiont in lichens and has previously been found in species such as Xanthoria parietina from Europe ( Beck and Mayr, 2012 ;Nyati et al, 2013 ;Nyati et al, 2014 ) and in X. hasseana from western North America ( Werth, 2012 ).…”

Microclimatic differentiation of gene pools in theLobaria pulmonariasymbiosis in a primeval forest landscape

“…Free-living photobionts must be able to survive without the positive effect of ecological buffering provided by the mycobiont. There is a growing body of evidence that lichen photobionts are specialized to particular habitats and ecological conditions (Piercey-Normore 2006;Yahr et al 2006;Werth & Sork 2010;Casano et al 2011;Fernandez-Mendoza et al 2011;del Hoyo et al 2011;Peksa & Skaloud 2011;Werth 2012;del Campo et al 2013;Domaschke et al 2013). Our study is in concordance with those studies and showed a distinct ecological, that is altitudinal, niche differentiation in the photobiont Dictyochloropsis eticulata (Table 4, Fig.…”

Comparison of phylogeographical structures of a lichen‐forming fungus and its green algal photobiont in western North America

“…decolorans that is much more broadly distributed than the lichen‐forming fungus R. menziesii , and this suggests that this algal species has very different environmental tolerances. T. decolorans has been reported from several continents and in association with diverse fungal species (Helms et al ., ; Beck & Mayr, ; Werth, ; Muggia et al ., ; Nyati et al ., ,b). The wider distributional range and low specificity of T .…”

“…In contrast, the green alga T. decolorans that is much more broadly distributed than the lichen-forming fungus R. menziesii, and this suggests that this algal species has very different environmental tolerances. T. decolorans has been reported from several continents and in association with diverse fungal species (Helms et al, 2001;Beck & Mayr, 2012;Werth, 2012;Muggia et al, 2013;Nyati et al, 2013a, b). The wider distributional range and low specificity of T. decolorans imply that this photobiont may have persisted under more diverse environmental conditions and experienced a population history distinct from the mycobiont R. menziesii.…”