Abstract
Members of the genus Dermatocarpon are widespread throughout the Northern Hemisphere along the edge of lakes, rivers and streams, and are subject to abiotic conditions reflecting both aquatic and terrestrial environments. Little is known about the evolutionary relationships within the genus and between continents. Investigation of the photobiont(s) associated with sub-aquatic and terrestrial Dermatocarpon species may reveal habitat requirements of the photobiont and the ability for fungal species to share the same photobiont species under different habitat conditions. The focus of our study was todetermine the relationship between Canadian and Austrian Dermatocarpon luridum var. luridum along with three additional sub-aquatic Dermatocarpon species, and to determine the species of photobionts that associate with D. luridum var. luridum. Culture experiments were performed to identify the photobionts. In addition, the question of the algal sharing potential regarding different species of Dermatocarpon was addressed. Specimens were collected from four lakes in northwestern Manitoba, Canada and three streams in Austria. Three Canadian and four Austrian thalli of D. luridum var. luridum were selected for algal culturing. The nuclear Internal Transcribed Spacer (ITS) rDNA gene of the fungal partner along with the algal ITS rDNA gene was sequenced to confirm the identity of the lichen/photobiont and afterwards the same data sets were used in phylogenetic analyses to assess algal sharing. The green algal photobiont was identified as Diplosphaera chodatii (Trebouxiophyceae). The phylogenetic analyses of Canadian and Austrian D. luridum var. luridum revealed that ITS sequences are identical despite the vast geographic distance. Phylogenetic placement of D. luridum var. decipiens and D. arnoldianum suggested that a re-examination of the species status might be necessary. This study concluded that additional photobiont culture experiments should be conducted to answer the question of whether multiple photobionts are present within the genus Dermatocarpon.
Highlights
The vast majority of lichens involve the association of a heterotrophic fungus of the Ascomycota and a photoautotrophic alga of the Chlorophyta [1]
An additional algal culture, which was isolated from D. luridum var. luridum thallus collected in Canada, revealed two different algal cell types (Figure 1D)
Additional specimens from Europe are closely associated with the Austrian representatives, while the additional specimens from North America fall out in three sub-clades
Summary
The vast majority of lichens involve the association of a heterotrophic fungus of the Ascomycota and a photoautotrophic alga of the Chlorophyta [1]. The majority of lichen species that live in or associated with aquatic ecosystems are systematically positioned within the Verrucariaceae. Many genera within the Verrucariaceae do not form monophyletic clades, but the genus Dermatocarpon. Some Dermatocarpon species colonize rock substrata that are associated with watercourses, which periodically inundate the lichen thalli; such lichens are considered ―sub-aquatic‖ lichens [8,9]. Other members of Dermatocarpon are not associated with watercourses and live on rocks and occasionally on soil. Members of this genus exhibit rather diverse morphologies, while other commonly known sub-aquatic species include: Dermatocarpon arnoldianum, D. luridum var.
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