Global Biodiversity Patterns of the Photobionts Associated with the Genus Cladonia ( Lecanorales , Ascomycota )
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FUNGAL MICROBIOLOGY
Global Biodiversity Patterns of the Photobionts Associated with the Genus Cladonia (Lecanorales, Ascomycota) Raquel Pino-Bodas 1
&
Soili Stenroos 2
Received: 19 August 2020 / Accepted: 22 October 2020 # The Author(s) 2020
Abstract The diversity of lichen photobionts is not fully known. We studied here the diversity of the photobionts associated with Cladonia, a sub-cosmopolitan genus ecologically important, whose photobionts belong to the green algae genus Asterochloris. The genetic diversity of Asterochloris was screened by using the ITS rDNA and actin type I regions in 223 specimens and 135 species of Cladonia collected all over the world. These data, added to those available in GenBank, were compiled in a dataset of altogether 545 Asterochloris sequences occurring in 172 species of Cladonia. A high diversity of Asterochloris associated with Cladonia was found. The commonest photobiont lineages associated with this genus are A. glomerata, A. italiana, and A. mediterranea. Analyses of partitioned variation were carried out in order to elucidate the relative influence on the photobiont genetic variation of the following factors: mycobiont identity, geographic distribution, climate, and mycobiont phylogeny. The mycobiont identity and climate were found to be the main drivers for the genetic variation of Asterochloris. The geographical distribution of the different Asterochloris lineages was described. Some lineages showed a clear dominance in one or several climatic regions. In addition, the specificity and the selectivity were studied for 18 species of Cladonia. Potentially specialist and generalist species of Cladonia were identified. A correlation was found between the sexual reproduction frequency of the host and the frequency of certain Asterochloris OTUs. Some Asterochloris lineages co-occur with higher frequency than randomly expected in the Cladonia species. Keywords Asterochloris . Lichens . Specificity . Symbiosis . Trebouxiophyceae
Introduction A lichen has been traditionally considered as a stable symbiotic association between a fungus (mycobiont) and at least a green alga or a Cyanobacterium (photobiont) [1]. However, a recent study considered a lichen to be a self-sustaining ecosystem constituted by a mycobiont, one or more photobionts, and a number of other microorganisms [2]. The photobionts Supplementary Information The online version contains supplementary material available at https://doi.org/10.1007/s00248-02001633-3. * Raquel Pino-Bodas [email protected] 1
Comparative Plant and Fungal Biology, Royal Botanic Gardens, Kew, Richmond TW9 3DS, UK
2
Finnish Museum of Natural History, University of Helsinki, P.O. Box 7, Helsinki 00014, Finland
transfer to the mycobiont, in form of polyols or glucose, the carbon they have fixed during photosynthesis. The mycobiont uses these compounds for its nutrition and for synthesizing secondary metabolites. For its part, the mycobiont provides the photobiont with adequate light, humidity, and gas exchange, which allows it to carry out the
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