Didimosphenia geminata: sequences and morphology data set

<p><span>Microalgae and their invasiveness are recurrent themes in aquatic environments and many invasions by microalgae are linked to eutrophication. However the diatom <i>Didymosphenia geminata </i>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 <i>D. geminata</i> 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 <i>D. geminata</i> 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.</span></p>