Characterization of Hawaiian freshwater and terrestrial cyanobacteria reveals high diversity and numerous putative endemics

Fifty samples of cyanobacteria were collected and characterized as part of the Hawaiian Freshwater Algal Biodiversity Survey. Fifty-two percent of the samples originated from Oahu, while the remainder were collected from Kauai (14%), Maui (20%) and Hawaii (14%). A diversity of habitats (e.g. streams, wet walls, taro fields, terrestrial areas and ditches) was represented by the collection sites, which is reflective of the abundance of suitable non-marine algal substrata in these isolated, humid, subtropical islands. Most samples were isolated and cultured for observation of morphological features, and all were sequenced for both the Universal Plastid Amplicon (UPA) marker (partial 23S rRNA) and 16S rRNA gene. Alignments of both markers (separately and concatenated) with additional GenBank sequences for phylogenetic representation were analyzed using Maximum Likelihood, Bayesian and Maximum Parsimony approaches. Nodal support was highest for the concatenated UPA+16S rRNA gene alignment, and phylogenetic analyses indicated a monophyletic Nostochophycidae, and monophyly, although with low support, for the Oscillatoriophycidae and Synechococcophycidae. A conservative estimate is that 11 of the taxa are putative endemics to the Hawaiian Islands, further highlighting the uniqueness of this isolated and understudied flora, and the potential for discovery of novel taxa through taxon-focused biodiversity surveys.