Genotypic and phylogenetic diversity of new isolates of terrestrial Xanthophyceae (Stramenopiles) from maritime sandy habitats

ABSTRACT

Xanthophyceae (Stramenopiles) are common microalgae in soil habitats, but not commonly known from maritime sandy habitats. Here we studied the genetic diversity of nine new isolates of Xanthophyceae from coastal habitats using two chloroplast-encoded markers. The isolates exhibited only three morphotypes. The sequence comparisons uncovered a respectable phylogenetic diversity, including novel infraspecific genotypes, among the isolates. The phylogenetic analyses of full rbcL gene sequences identified eight of the isolates to five named species based on monophyletic origins and short genetic distances with defined taxonomic reference strains. One strain, representing a coccoid species, was within a so far unrecognised lineage of Xanthophyceae. In four clades of the rbcL phylogeny, the coastal isolates were most closely related to strains from Antarctic soil habitats. Comparisons of the psbA/rbcL spacer region sequences, a highly variable molecular marker, uncovered a fine-scale structuring within a species which was consistent with habitat preferences. The new maritime isolates exhibited genotypes distinct from those of the same species from other habitats. It suggests that the environment selects for specific genotypes in these pioneering algae.

KEYWORDS:

• BSCs (Biological Soil Crusts)
• Intraspecific genotypic variation
• Maritime sandy habitat
• Stramenopile algae
• Xanthophyceae

ACKNOWLEDGEMENTS

TM acknowledges the Alexander von Humboldt Foundation for financial support (Georg-Forster research fellowship at the University of Rostock) and Ulf Karsten for provision of laboratory facilities and his support of collecting samples from the Baltic Sea coast. We thank Maike Lorenz for provision of well-curated algal strains from the SAG culture collection and accession of the new Xanthophyte isolates. Henrike Ledel and Hella Timmermann are acknowledged for the purification of Xanthophyceae strains, and Gabriele Curdt-Hollmann for assistance in sequencing strains of Xanthophyceae. We thank Ladislav Hodač for provision of an isolate of Xanthonema from soil, and the Culture Collection of Algae and Cyanobacteria at the Institute of Botany, Třeboň, Czech Republic, for provision of strain CCALA 518.

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Funding

This work has been funded by the German Science Foundation (DFG) Priority Program 1991 ‘Taxon-OMICS’ (Project RY 173/1-1, extended to NR).