Discovery of new cyanobacterial species from crusted soils of San Nicolas Island, California, from genera previously restricted to Brazil and Africa.

We are currently revisiting a study by Flechtner, Johansen, and Belnap (2008) on the algae of biological soil crusts on San Nicolas Island.  A total of 200+ strains have been newly isolated, of which 78 cyanobacterial strains have been sequenced, representing 26 different species.  Of these 26 species, 23 appear to be phylogenetically new to science.  Several isolates show distinctive biogeography, belonging to genera recently described from Brazil. We found evidence of three species of the heterocytous genus Atlanticothrix, two species of Pycnacronema, and one species of Konicacronema.  Our species are morphologically consistent with species of these genera, but molecularly are clearly separated, particularly on the basis of ribosomal gene trees and analysis of the 16S-23S internal transcribed spacer region. There are presently no known vectors for transmission of taxa from the Atlantic Forest in Brazil to San Nicolas Island, or vice versa.  Wind patterns from Africa are known to bring dust from that continent to both South America and North America, but winds in the western hemisphere blow out into the Pacific Ocean in a westerly direction and do not cross the equator.  This suggests that at some time in the distant past, these microbes may have been seeded from Africa to North America, but have been in place long enough to become independent distinctive lineages worthy of recognition as different species from their southern hemisphere congeners. As preliminary evidence supporting an African origin for soil crust taxa, other workers have reported cyanobacterial genera in Africa (Pseudoacaryochloris, Aliterella, and Atlanticothrix) that also occur on San Nicolas Island. Future work will explore the cyanobacterial flora of all the Channel Islands as well as coastal southern California which could serve as a colonization source for cyanobacteria on the islands.