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Didimosphenia geminata: sequences and morphology data set

Citation

Cardenas, Leyla (2020), Didimosphenia geminata: sequences and morphology data set, Dryad, Dataset, https://doi.org/10.5061/dryad.gb5mkkwn4

Abstract

Microalgae and their invasiveness are recurrent themes in aquatic environments and many invasions by microalgae are linked to eutrophication. However the diatom Didymosphenia geminata has gained notoriety in forming thick mucilaginous mats in pristine, rocky-bottomed rivers with no obvious connection to elevated levels of nutrients. This species is native to freshwaters of the circumboreal region of the Northern Hemisphere and blooms in the Southern Hemisphere have been attributed to recent introductions of the species to these regions. Although regional population genetic analyses have suggested multiple recent introduction of this species, the gene flow and the spatial genetic diversity distribution on a global scale remains unknown. We develop a phylogeographic analysis to investigate the genetic diversity of D. geminata populations around the globe. Our results indicate two distinct genetic lineages geographically distributed that remain spatially isolated. One lineage is exclusively found in Europe, the other is distributed in North America, New Zealand and South America. Since blooms of D. geminata commenced in North America and in Europe simultaneously, these data support the idea that factors associated with global environmental change and possibly the associated biome are the cause of blooms globally. We further discuss the role of human mediated-dispersal.

Methods

Sampling collection.
A total of 55 samples of didymo were collected in Spain, Italy, Polonia, Russia, Canada, Chile, Argentina and New Zealand. Samples were stored in 90% ethanol or in RNA-later solution for posterior analyses. Didymo cells were measured using a light microscopy (LM) and a scanning electron microscope (SEM). LM observations were performed using an inverted Leitz Fluovert microscope. SEM observations were performed in the UMI core facility (http://microscopiaelectronica.uach.cl). Morphometric analysis of didymo samples from Argentina (n=2), Chile (n= 6), Canada (n=6), Spain (3) and Italy (n=2) was run considering maximum length, maximum width, head pole width and foot pole width of cells. Morphometric variability of cells among samples were tested using one way-ANOVA. 

Total DNA was extracted using the CTAB plus Proteinase K protocol. Target genes were two nuclear genes, the large (LSU) and the small (SSU) ribosomal subunits rDNA and two mitochondrial markers, the cytochrome oxidase B (COB) and the NADH dehydrogenase subunit 6 (NAD-6). All PCRs were performed in a final volume of 12.5 mL containing 2.5 ml of buffer 5X, 1.5 ml of MgCL2 (5mM), 0.25 of dNTPs (0.2mM each one), 0.125 ml for each primer (10um), 1 ml of BSA (0.24 mg/ml), 0.0625 ml GoTaq (0.025U), 5.375 ml milli Q water, and 1 ml of total DNA. Amplicons were purified using E.Z.N.A. Cycle Pure Kit (Omega Bio-tek) and sequenced at the core facility Austral-omics (www.australomics.cl) using an ABI-3500 sequencer. Sequences edition and alignments were performed using the bioinformatics software Geneious Pro.

Funding

Agencia Nacional de Investigación y Desarrollo, Award: Fondecyt 1170591

Agencia Nacional de Investigación y Desarrollo, Award: (FONDAP) programme Research Center 15150003