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

Abstract

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 123Biodivers Conserv (2015) 24:739-757 DOI 10.1007 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.

Cyanobacterial biodiversity and associated ecosystem services: introduction to the special issue

“…Cyanobacterial taxonomy still requires a consensus approach (Palinska and Surosz 2014) (Oren and Garrity 2014;Imhoff 2014;Pinevich 2014). An overview on cyanobacterial taxonomy, species concepts, and speciation factors having significant impact on their biodiversity status are elaborated by Dvořák et al (2015). Unexplored biodiversity of terrestrial cyanobacteria present on natural and anthropogenic stone surfaces around the world, and their ecological significance, is reviewed by Hauer et al (2015).…”

Difference without distinction? Gaps in cyanobacterial systematics; when more is just too much

“…On another front, practical identifications of cyanobacteria (for applied phycology, ecology, and genetics) are still obtained mainly using morphological observations which may be increasingly problematic as more polyphyletic lineages are elucidated and rarely revised. Further, there is a lack of morphological apomorphies for some newly described lineages (Komárek et al 2014;Dvořák et al 2015b). The potential use of cyanobacteria for environmental bioassessment and biomonitoring efforts is largely limited by available sequence data (for those employing genetic markers) and proper species descriptions using phenotypic data (e.g.…”

“…This might be illustrated with Leptolyngbya nodulosa which was originally described and phylogenetically analyzed with rather depauperate sister and outgroup taxa (all that was available at the time) before subsequently being transferred to a new genus. Revisions using only phenotypic data are discouraged, due to serial convergence of morphotypes (Dvořák et al , 2015b. It should be noted that cyanobacteria have a relatively rich herbaria presence in museums, and thus an investigation of type material is often possible and recommended (Komárek et al 2014;Palinska & Surosz 2014).…”

A new cyanobacterium from the Everglades, Florida - Chamaethrix gen. nov.

“…These events have given rise to the polyphyletic relationships within a majority of cyanobacterial genera, necessitating taxonomic revisions and description of many new taxa (e.g. komárek et al 2014; Dvořák et al 2015). Moreover, morphologically simple genera with wide ecological and biogeographical ranges, such as the unicellular Synechococcus or filamentous Leptolyngbya, may mask numerous polyphyletic lineages (OsOriOsantOs et al 2014;misCOe et al 2016;Dvořák et al 2017).…”