Felix Bast, Satej Bhushan, Aijaz Ahmad John, Jackson Achankunju, Nadaraja Panikkar MV, Christina Hametner and Elfriede Stocker-Wörgötter
In 2011, isolated parts in south Indian state of Kerala as well as neighboring Sri Lanka experienced sporadic spell of red colored “blood rain”, cause of which was later attributed to terrestrial subaerial microalgae of the genus Trentepohlia. Green algae of this genus is commonly found living in symbiosis as phycobionts of lichens in the freeliving form in adjoining tropical rain forests, however, specific identity of which have never been determined. It is known that lichens disperse small algal-hyphal packages, so-called soredia, for vegetative reproduction, which can explain the content of Trentepohlia-spores in the water. Given its extraordinary spore-dispersal mechanism via rain, we were specifically interested to know species-level identity of a randomly collected Trentepohlialean algae of “blood rain” region, and to investigate the possibility that this might had been introduced from elsewhere through areal route. Results of our comparative morphology and molecular phylogenetic analyses using the nuclear ribosomal DNA Internal Transcribed Spacers region concluded that this alga is Trentepohlia annulata – a species of which no previous reports exist from India. These two geographical isolates were separated by Kimura-2-Parameter pair-wise distance of 0.06-which in turn indicate a low rate of evolution at these loci that are renowned for rapid molecular evolution, suggestive of a recent introduction. Phylogeny reconstruction using Bayesian Inference and Maximum Likelihood methods resulted in well-resolved phylograms with a robust clade composed of these isolates. This finding indicates the existence of areal dispersal of algal spores on continental and global scales through “clouds over oceans”- a phenomenon earlier reported for bacteria and fungi, but for the first time in algae.
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