Species concepts and speciation factors in cyanobacteria, with connection to the problems of diversity and classification

The cyanobacteria are the most important prokaryotic primary producers on Earth, inhabiting a great diversity of aquatic and terrestrial environments exposed to light. However, the evolutionary forces leading to their divergence and speciation remain largely enigmatic compared to macroorganisms due to their prokaryotic nature, including vast population sizes, and largely asexual reproduction. The advent of modern molecular techniques has facilitated an understanding of the important factors shaping cyanobacterial evolution, including horizontal gene transfer and homologous recombination. We review the forces shaping the evolution of cyanobacteria and discuss the role of cohesive forces on speciation. Further, while myriad species concepts and definitions are currently used, only a limited subset might be applied to cyanobacteria due to their asexual reproduction. Additionally, concepts based solely on phenotypes provide insufficient resolution. A monophyletic species concept which is universal may be ideal for cyanobacteria. Actual identification of the cyanobacteria is difficult due to cryptic diversity, lack of morphological variability, and frequent convergent evolutionary events. Thus, applied molecular techniques such as DNA barcoding will be useful for identifications of environmental samples. Lastly, we show that the real biodiversity of the cyanobacteria is widely underestimated, due in part to low sampling efforts, sensitivity to the molecular markers employed, and the species definitions employed by researchers. In conclusion, we anticipate a rapid increase in cyanobacterial taxa described and large revisions of the system in the future as scientists adopt a common approach to cyanobacterial systematics

Phylogeography of the Microcoleus vaginatus (Cyanobacteria) from Three Continents – A Spatial and Temporal Characterization

It has long been assumed that cyanobacteria have, as with other free-living microorganisms, a ubiquitous occurrence. Neither the geographical dispersal barriers nor allopatric speciation has been taken into account. We endeavoured to examine the spatial and temporal patterns of global distribution within populations of the cyanobacterium Microcoleus vaginatus, originated from three continents, and to evaluate the role of dispersal barriers in the evolution of free-living cyanobacteria. Complex phylogeographical approach was applied to assess the dispersal and evolutionary patterns in the cyanobacterium Microcoleus vaginatus (Oscillatoriales). We compared the 16S rRNA and 16S-23S ITS sequences of strains which had originated from three continents (North America, Europe, and Asia). The spatial distribution was investigated using a phylogenetic tree, network, as well as principal coordinate analysis (PCoA). A temporal characterization was inferred using molecular clocks, calibrated from fossil DNA. Data analysis revealed broad genetic diversity within M. vaginatus. Based on the phylogenetic tree, network, and PCoA analysis, the strains isolated in Europe were spatially separated from those which originated from Asia and North America. A chronogram showed a temporal limitation of dispersal barriers on the continental scale. Dispersal barriers and allopatric speciation had an important role in the evolution of M. vaginatus. However, these dispersal barriers did not have a permanent character; therefore, the genetic flow among populations on a continental scale was only temporarily present. Furthermore, M. vaginatus is a recently evolved species, which has been going through substantial evolutionary changes

Blue-green algae (cyanobacteria) in rivers

This chapter presents some of the more commonly encountered lotic cyanobacterial taxa. The cyanobacteria are a group of oxygenic prokaryotes present in nearly all aquatic ecosystems. While the ecological importance of this lineage is well known, much confusion exists pertaining to their systematic and taxonomic status. In order to facilitate generic-level identification, we separate the cyanobacteria into four major groupings: the Chroococcales (coccoid cells often in a mucilaginous envelop), the Oscillatoriales (filamentous forms lacking specialized cells), the Nostocales (filamentous with inducible specialized cells), and the Stigonematales (filamentous, obligatory specialized cells coupled with cell division in multiple planes). We discuss the major genera found in each lineage, the current state of the systematics, and the broad ecological roles and niches of these taxa. Dichotomous keys and images are presented to facilitate generic identifications

Jacksonvillea apiculata (Oscillatoriales, Cyanobacteria) gen. & sp. nov.: A new genus of filamentous, epipsamic cyanobacteria from North Florida

Two strains of an unusual, filamentous, Geitlerinema-like cyanobacterium inhabiting sandy sediments in Lake Oneida (Jacksonville, Florida) were isolated. These strains possessed a unique combination of specific morphological and molecular characters that enable the establishment of a new monospecific genus on the basis of the type species Jacksonvillea apiculata sp. nov. named in honor of the city of Jacksonville. Morphologically, the species differed from Geitlerinema splendidum and other representatives of the genus Geitlerinema by the presence of spherical structures in the cell walls at cross-walls. Similarly, sequences of the 16S ribosomal RNA gene were below the currently accepted similarity for inclusion into the same genus (i.e. 86% sequence similarity), and were most similar to Desertifilum (88%). To acknowledge the high difference of the Jacksonvillea-Desertifilum clade from members of the family Coleofasciculaceae, we established the new family Desertifilaceae fam. nov., which formed a poorly supported sister clade to some unclear Geitlerinema such the black-band disease strains

The dating of the divergence times among cyanobacteria.

<p>Maximum credibility chronogram based on 16S rRNA of cyanobacteria, with an emphasis on <i>Microcoleus vaginatus</i>. It is a continuation of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0040153#pone-0040153-g005" target="_blank">Figure 5</a>. The mean ages and confidence intervals (95% HPD) are indicated at the nodes. The studied strains are in bold. The geographic origin of each strain is indicated as E – Europe, A – Asia, and NA – North America. A plus mark indicates the strains which have been identified anew because of previous incorrect determinations in the culture collection. An asterisk represents a node where <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0040153#pone-0040153-g005" target="_blank">Figure 5</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0040153#pone-0040153-g006" target="_blank">6</a> were originally connected.</p

Underestimated cyanobacterial diversity: Trends and perspectives of research in tropical environments

Cyanobacteria are photo–oxygenic prokaryotes present in nearly all ecosystems, where they are important in global oxygen, carbon, and nitrogen cycles. They are often recognized as the harbingers of eutrophication in freshwater systems and are increasingly being noted as nuisance species in marine ecosystems such as coral reefs. In recent years, cyanobacteria have been intensely studied due to their toxicity, harmful bloom formation, and because their distribution and abundance are expected to increase with climate change. Nevertheless, for all of their importance, many gaps in our knowledge of cyanobacteria remain: the distribution, dispersal, and biogeography of these microorganisms are still not understood. Until 1994 little attention was paid to tropical cyanobacteria and their diversity, despite some harmful invasive species having their putative origins in tropical habitats. However, more practiced articulation and research has recently uncovered previously undescribed biodiversity, and in turn changed our knowledge of the evolutionary relationships within the Cyanobacteria. The purpose of this paper is to describe the challenges of working with the cyanobacteria and to review what we know of them from tropical habitats

A novel genus Ammassolinea gen. nov. (Cyanobacteria) isolated from sub–tropical epipelic habitats

A new monospecific genus of an epipelic, filamentous oscillatorean Phormidium-like cyanobacterium is established. The genus was first discovered from a pond at Fiddlers Ridge Drive, Jacksonville, Florida, USA and subsequently isolated into uni-algal strains. During the process of cultivation, a combination of morphological, ultrastructural and molecular evidence supports the erection of a novel genus. Based on apomorphies which differ from related taxa such as heap-like colony formation, ultrastructural properties and molecular uniqueness, we propose the generic epithet Ammassolinea (sand-dwelling filaments)