Introduction: Recent developments in cyanobacterial research with special reference to aquatic habitats, molecular ecology and phylogenetic taxonomy

The global importance of cyanobacteria is well known from their worldwide distribution and abundance as well as their contribution to atmospheric oxygen. In spite of a long history of cyanobacterial research in microbiology and botany, only a small portion of their high diversity has been recovered and only recently been addressed by molecular and phylogenetic methods. Controversies in traditional and modern approaches to cyanobacterial taxonomy still persist, which has stimulated their discussion within the 20th IAC Symposium. In this special section, we present a set of nine contributions, selecting the most interesting outcomes of the meeting. The molecular approaches applied deal on one hand, with classical single and multilocus phylogenetic taxonomy methods, on the other hand with high-throughput next generation sequencing methods to rapidly identify diversity of cyanobacteria in environmental samples without the possibility to investigate their taxonomic status in depth. The studied ecosystems include a variety of freshwater, brackish and marine, planktonic and benthic habitats from which cyanobacteria were sampled. Study regions comprise temperate, arctic, alpine and tropical environments from four continents. We discuss the salient points of the contributions from this volume and formulate four main issues from which conclusions are drawn in order to contribute to future progress in cyanobacterial research.