Comparative phylogeography of two free‐living cosmopolitan cyanobacteria: Insights on biogeographic and latitudinal distribution

Abstract

Aim: Free-living bacteria have long been assumed to have little biogeographic signature because of their high potential for passive dispersal. Raphidiopsis raciborskii and Microcystis aeruginosa are free-living cosmopolitan cyanobacteria with a probable tropical origin, that frequently form toxic blooms and are considered invasive species in middle latitudes. Despite these similarities, their phylogeographic patterns have seldom been directly compared. Our aim was to reconstruct the phylogeographic histories of R. raciborskii and M. aeruginosa, in order to explore whether their current distributions could be attributed to the same biogeographic events. Location: Global.Taxa: Raphidiopsis raciborskii (Nostocales) and Microcystis aeruginosa (Chroococcales). Methods:The phylogeography of these species was studied based on global genetic diversity patterns from a dataset of worldwide 16S rRNA gene sequences. Genetic diversity indices were measured globally and by latitude. Analyses based on distance matrices were performed to evaluate the correlation between genetic divergence, geographic distance and climatic conditions. Demographic history was investigated through neutrality tests and Bayesian Skyline Plot analysis.Results: For both species, the genetic diversity is highest in tropical latitudes, and the data provided evidence of recent population expansions (in the last 2,500 years). R. raciborskii showed much lower genetic diversity than M. aeruginosa. A significant phylogeographic structure was found for R. raciborskii but not for M. aeruginosa. Climatic conditions had a significant influence on the genetic structure of both species, but this influence was stronger and varied according to latitude only for R. raciborskii. Main Conclusions:Supporting the hypothesis of a tropical origin and recent dispersal to temperate habitats, both species had higher genetic diversity in tropical latitudes and showed evidence of recent population expansions. R. raciborskii populations showed a significant decline in genetic similarity with increasing geographic distance, indicating an interaction between drift and some dispersal limitation on its phylogeography. In contrast, M. aeruginosa seemed to have a high frequency of intercontinental dispersal. Finally, the particularities of each species, such as the ability to form akinetes in R. raciborskii and high genome plasticity and niche specialization in M. | 1107 RIBEIRO Et al.

Environmental conditions are more effective than nutrient availability and spatial processes on explaining microphytoplankton functional structure in a subtropical hypereutrophic reservoir

“…The variability of purely ENV component explained 45% of the variance in MBFG's biovolume and this component was mainly composed of abiotic predictors showing high seasonal variation (insolation, precipitation, water The key role of seasonal variability of environmental factors in structuring microphytoplankton community in the It a reservoir remains more evident when we observed the relative biovolume and the seasonal distribution of the most abundant MBFGs (MBFG III and V). Rising temperatures and increased organic and nutrient loading, for instance, were pointed as key drivers determining bloom events of the most large filamentous cyanobacteria that represent the MBFG III (Tucci and Sant'Anna, 2003;Viney et al 2007;Okello & Kurmayer 2011;Kosten et al 2012;O'Neil et al 2012;Paerl & Otten 2013;Lv et al 2014;Dao et al 2016;Haakonsson et al 2017;Simi c et al 2017;Bel o et al 2018;Braga & Becker 2020;Ribeiro et al 2020). This support our results that showed an important relative biomass of the MBFG III in the spring and summer samples, when high water temperatures were combined to increased precipitation, which possibly increase the load of allochthonous resources in these seasons.…”

Recent Advances in the Ecology of Bloom-Forming Raphidiopsis (Cylindrospermopsis) raciborskii: Expansion in China, Intraspecific Heterogeneity and Critical Factors for Invasion

“…In the past decades, the occurrence frequency of this species has been significantly increased over the world, including both subtropical and temperate zones of the globe [7,9,10]. Therefore, R. raciborskii was suggested to be an invasive cyanobacterium, and much attention has been paid to its dispersion routes and adaptation mechanisms [9,11,12]. Based on the phylogenetic relationship of strains isolated worldwide, three hypotheses have been proposed for the biogeographic origin and global dispersion of R. raciborskii [7].…”

The CRISPR/Cas Machinery Evolution and Gene Flow in the Hot Spring Cyanobacterium Thermostichus

“…This assumption seems to be working when only morphological characters are analyzed (e.g., [9]), but microorganisms possess relatively low morphological diversity in comparison with genome diversity. Molecular phylogeny provided evidence for the geographical structuring of microbial species in prokaryotes (e.g., [10,11]). Possible geographical isolation was also identified in cyanobacteria, e.g., in Microcoleus [12], and thermophilic cyanobacteria (see below).…”