Acceleration of Biodiversity Assessment (ABA): Changes in the diversities of terrestrial microalgae and cyanobacteria (including lichen symbionts) along an altitudinal gradient in a tropical mountain forest
Final Report Abstract
This project aimed at assessing the diversity of terrestrial microalgae in a tropical rain forest of Ecuador in various habitats, i.e. the surfaces of tree bark and leaves, upper layers of soil and lichen symbiosis with the green algae (Chlorophyta) as example. Using mainly a culture-independent approach to reveal molecular marker signatures from the 18S (as a phylogenetic tag) and ITS2 rRNA genes (for reidentification of species and strains at a high resolution) simultaneously for the same environmental clones, the diversity of terrestrial green algae (incl. a genus of lichenized algae) was studied along an altitudinal gradient from 1000 to 3000 meters a.s.l. Sixteen 18S phylotypes within the Trebouxiophyceae, a group of closely related Scenedesmaceae, Chlorophyceae (probably genus Coelastrella and/or close relatives with it) as well as numerous Operational Taxonomic Units (OTUs) representing the ulvophyte Trentepohlia were recorded in two or more out of a total of 40 samples which were collected at 17 defined research plots covering the three terrestrial habitats and three altitudinal levels. Evidence for a world-wide distribution of terrestrial green algae was found. In four genera the same or almost the same (98% identity) ITS2 sequences were recovered as already available from corresponding terrestrial habitats in Europe, i.e. Apatococcus, Coccomyxa, Heterochlorella and a lichenized species of Vulcanochloris. This may be explained by the fact that representatives of these genera are robust aerophytic algae that exhibit desiccation tolerance or are protected by the association with a lichen fungus both facilitating long-distance dispersal. At the same time new lineages of green algae, so far only known from the study sites, were revealed, i.e. within genera known to be distributed also outside of the tropics, i.e. Apatococcus, Coccomyxa, Chloroidium, Trebouxia and the Scenedesmaceae. This may indicate that these genera are so diverse in the study area that new and so far not formally described lineages can be recovered. Our study allowed a thorough analysis of three terrestrial habitats in a rather limited geographical region within short time whereas similar studies in other regions have not been preformed systematically and rather represent numerous single findings that have accumulated over a longer period of time. Therefore, also the simple effect of “well sampled at the study sites, but clearly undersampled elsewhere” may account for this, despite the above mentioned genera seem to be reasonably well sampled based on the numerous sequence records in NCBI/Genbank available for them. Phyllosiphon and Heveochlorella were the OTU-richest trebouxiophyte phylotypes, but only a tiny fraction of the diversity recovered in our study has already been known from elsewhere. Both sub-projects of our study converged in diversity analyses of the trebouxiophyte genus Symbiochloris which was found in lichen symbioses as well as outside of any clearly visible lichen associations on surfaces of leaves and tree bark. Our study area appeared as a diversity hotspot of Symbiochloris. Its abundant and diverse occurrence outside from lichen associations was unexpected given the few species so far known to occur free-living, i.e. more than 30 ITS2 CBC–clades were recovered. The concept of distinguishing ITS2 CBC-clades within a green algal genus seems to be appropriate for those genera within which CBCs can be detected. Several of the recovered Symbiochloris CBC clades corresponded to currently recognized species. In contrast, there seem to be only three (yet unnamed) species lichenized in the study area with two of them (S3 and S7) probably restricted to lichen symbioses. Interestingly, he many studied specimens (>300) of Lobaria and Sticta were found all associated with a probably single species of Symbiochloris, the yet not formally described S3, but several divergent lineages may occur within that lineage. The diversity and distribution patterns of the Symbiochloris S3 photobionts still need to be explored furthermore.
Publications
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(2012) Molecular evidence for the wide distribution of two lineages of terrestrial green algae (Chlorophyta) over tropics to temperate zone. ISRN Ecology: 9
Hodač L, Hallmann C, Rosenkranz H, Faßhauer F, Friedl, T
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(2014) Molecular phylogeny and symbiotic selectivity of the green algal genus Dictyochloropsis s.l. (Trebouxiophyceae) a polyphyletic and widespread group forming photobiont-mediated guilds in the lichen family Lobariaceae. New Phytologist 202: 455-470
Dal Grande F, Beck A, Cornejo C, Singh G, Cheenacharoen S, Nelsen MP, Scheidegger C
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(2015) Metabolic Profiling of Alpine and Ecuadorian Lichens. Molecules 20: 18047-18065
Mittermeier VK, Schmitt N, Volk LPM, Suárez JP, Beck A, Eisenreich W
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(2016) Taxonomic revision and species delimitation of coccoid green algae currently assigned to the genus Dictyochloropsis (Trebouxiophyceae, Chlorophyta). Journal of Phycology
Škaloud P, Friedl T, Hallmann C, Beck A, Dal Grande F
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(2016) Widespread green algae Chlorella and Stichococcus exhibit polar-temperate and tropical-temperate biogeography. FEMS Microbiology Ecology, Volume 92, Issue 8, 1 August 2016, fiw122
Hodac L, Hallmann C, Spitzer K, Elster J, Faßhauer F, Brinkmann N, Lepka D, Diwan V, Friedl T
