Pseudoacaryochloris (Acaryochloridaceae, Cyanobacteria) species from Africa and North America: a disjunct distribution suggesting transatlantic wind dispersal.

Cyanobacteria are critical primary producers not only in the world’s aquatic environments but also in terrestrial environments, where their role in microbial food webs is just starting to be revealed. Two new species of Pseudoacaryochloris, a recently described coccoid cyanobacterial genus from hypolithic and endolithic aridland habitats in the Sahara desert, were found in temperate-climate terrestrial habitats in Ethiopia and on San Nicolas Island, California. The Ethiopian isolate showed closer genetic affinity with the San Nicolas Island strain than either did with the Saharan species. According to molecular evidence—including 16S rRNA gene similarity and phylogeny, and 16S–23S ITS dissimilarity, phylogeny, and secondary structure of conserved domains—the Saharan populations of P. sahariensis were shown to actually represent 2 cryptic species. This rare genus has also been recovered in metagenomics studies of stone buildings and monuments both in Germany and in China. However, it has not been recovered in isolate-driven surveys or metagenomic studies in the Americas prior to this report, suggesting that the taxon is rare with limited distribution. The close genetic relationship of the San Nicolas Island species and the species found in Ethiopia, here described as P. cystiformans and P. abyssiniae, respectively, supports the hypothesis that dispersal of cyanobacterial species from arid soils in Africa has led to establishment of this genus in the Americas, followed by genetic lineage separation in the immigrant population(s). This dispersal and divergence has likely occurred due to infrequent extreme wind storms in Africa that bring dust particles to both the nearctic and neotropical Americas. [ABSTRACT FROM AUTHOR]