Mining the past for the future: cyanobacterial herbarium specimens for systematics, evolution, and cyanotoxin diversity.

While cyanobacteria are some of the most important primary producers on Earth, we still have limited understanding of their diversity and evolution. Herbarium collections offer a large and almost untapped source of cyanobacterial specimens. Here, we summarize the application of omics in the study of herbarium specimens of cyanobacteria which can enable us to advance our understanding of the diversity and evolution of this lineage. While we focus on taxonomic studies, where herbaria specimens have already uncovered novel diversity and resolved long-standing taxonomic conundrums by genome analysis of the type specimens, other uses abound. We show that herbaria can serve as instruments to investigate the impact of global changes based on amplicon sequencing. Further, researchers are discovering that cyanotoxins remain stable in the dried specimens, allowing for chemical analyses and novel compound discovery and exploration of past patterns in the cyanotoxin diversity in the environment. Ultimately, we would like to motivate researchers to utilize herbaria collections by outlining some of the possibilities of cyanobacterial-based herbaria samples.