Molecular Evidence for the Wide Distribution of Two Lineages of Terrestrial Green Algae (Chlorophyta) over Tropics to Temperate Zone

Phylogenetic analyses of 18S rDNA sequences from environmental clones and culture strains revealed a widespread distribution of two subaerial green algal lineages, Jenufa and Xylochloris, recently described from rainforests in southeast Asia. A new lineage of Jenufa (Chlorophyceae), most closely related to or even conspecific with J. minuta, was formed by sequences of European origin. Two more lineages of Jenufa were formed by three additional sequences from Ecuador and Panama. The other lineage was a close relative of Xylochloris irregularis (Trebouxiophyceae), probably representing a new species of the genus and distinct from the only so far described species, X. irregularis. It comprised two distinct clades each containing almost identical sequences from Germany and Ecuador. Analyses of the new sequences for both genera allowed to presume a preference of J. minuta to subaerial growth on rock or artificial hard substrates combined with a remarkable adaptation to extended periods of darkness, whereas Xylochloris may preferably occur on tree bark or in the soil. 1. Introduction The neutral dispersal model [1] suggests that microorganisms do not exhibit biogeography, that is, they are so small that no distribution barriers exist for them. This has been subject of debates by several authors, that is, geographic distribution was found in ciliates [2] and some microalgae [3]. A recent study based on 18S rDNA sequence comparisons provided evidence for endemism in an Antarctic habitat, that is, several new independent lineages of green algae were found in the benthos of an Antarctic lake [4, 5]. However, caution needs to be applied because there may still be an insufficient number of sequences available for many groups within the green algae. A lineage may appear “endemic” only as long as no other close relatives to it are known and this may easily change with the availability of new sequences from close relatives. In contrast to benthic freshwater algae, subaerial algae may be widely dispersed due to their remarkable adaptation to fast changing and adverse environmental conditions. Their resting cysts may easily survive transportation over long distances in the air being resistant to drought, high as well as low light intensities, and high UV radiation, for example, due to the presence of thickened cell walls or light protection pigments [6–9]. Recently, subaerial microalgae from southeast Asian tropical rainforest habitats gained increased interest by a series of studies [10–14] which lead to the establishment of two new genera of green algae, Jenufa [13]