Global ploidy levels of Phragmites australis

Phragmites australis is one of the most widely distributed macrophytes in the world and a model system for biological invasions, as both native and introduced lineages grow sympatrically across North America. Decades of research on this tall grass and its biotic and abiotic interactions have advanced our understanding of plant ecology and plant invasions, including evidence for the relationship between distribution and specific traits to particular ploidy levels within the species. Phragmites australis is characterized by its allopolyploid origins with a base chromosome number of x = 12, with tetraploids and octoploids dominating worldwide. While aneuploids of tetraploid plants have been documented with a total chromosome count around 48 modern high-resolution imaging has found only euploids in all samples. As P. australis chromosomes have large heterochromatin terminal knobs that break easily, earlier evidence of aneuploidy could be the result of artefactual aneuploid counts. The data published here represents samples the authors collected from the field and analyzed using flow cytometry and by extracting data from the published literature. Based on our own data and data extracted from the literature, we found that tetraploids of this species are the most widely distributed globally and are the dominant invasive ploidy level in North America. Higher ploidy levels are more restricted, particularly those greater than 8x.

Methods
This data sets consists of two types of ploidy data, observed samples from our common gardens either in Kingston, RI, USA or in Průhonice, Czechia which consisted of plants were collected from all over the world and grown in either garden and data extracted from published and unpublished literature. The method used to determine ploidy level is included for all ploidy values reported. All data are georeferenced.

Observed samples from our collection were freshly collected tissue samples from independent P. australis clones representing distinct populations obtained from the living collections curated at the University of Rhode Island, Kingston and the Institute of Botany, Czech Academy of Sciences, Průhonice, CZ. We also included some fresh tissue samples from field collections from plants not grown in our garden. These were transported to our lab in Průhonice, CZ on ice and analyzed immediately. All fresh samples were analyzed using flow cytometry and verified using chromosome counts.

For the ploidy data extracted from the literature, we carefully searched the Phragmites literature (Web of Science, Google Scholar, Scopus, extensive web search and cross-checked all published ploidy levels against populations in our own collection) for reported data on ploidy levels on P. australis using the following combination of key words: Phragmites australis, Phragmites communis, common reed, ploidy, polyploidy, chromosome, karyotype, and cytotype. We also searched the Chromosome Counts Database (http://ccdb.tau.ac.il/) to compile a comprehensive database of reported ploidy levels in P. australis and the location of their collections.

This data set represents a comprehensive global compilation of reported ploidy levels for P. australis ploidy levels.