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Effects of glaciation and whole genome duplication on the distribution of the Campanula rotundifolia polyploid complex

Citation

Sutherland, Brittany; Galloway, Laura F. (2021), Effects of glaciation and whole genome duplication on the distribution of the Campanula rotundifolia polyploid complex, Dryad, Dataset, https://doi.org/10.5061/dryad.hqbzkh1gp

Abstract

Premise Of The Study

Both intrinsic and extrinsic factors contribute to a species distribution. Among plants, the extrinsic effects of glaciation and intrinsic effects of whole genome duplication are powerful drivers of biogeographical patterns, but the interplay of these factors is poorly understood. Here, we investigate the roles glaciation and whole-genome duplication have played in the evolution of the widespread polyploid complex Campanula rotundifolia.

Methods

We assessed the cytotype of 37 populations that spanned the geographic and cytotypic range of the C. rotundifolia complex. We constructed a chloroplast phylogeny for these populations and used RAD-seq to create nuclear phylogenies and networks for a subset of 23 populations; and estimated divergence times of major clades using Bayesian estimation of substitution rates.

Key Results

Campanula rotundifolia originated in south-central Europe and underwent range expansion throughout much of Europe and North America. Multiple genome duplications have occurred in C. rotundifolia—at least two tetraploid and three hexaploid formations.

Conclusions

Nuclear and chloroplast phylogenies are largely congruent with a history of populations surviving glacial maxima in known Pleistocene refugia in Europe and North America. Divergent European clades are consistent with two disjunct glacial refugia within Europe. North America was colonized by hexaploids derived from Western European lineages. A glacial refugium in Midwestern North America likely facilitated post-glacial recolonization of North America and limited genetic divergence. These results implicate both glaciation and whole-genome duplication as contributing factors to the extant biogeography of C. rotundifolia.

Methods

This dataset consists of two DNA sequence alignments, one nuclear sdRAD DNA, one chloroplast DNA. All individual sequences are also archived in NCBI. Nuclear RADseq sequences are in the SRA archive (Accession SRP151156) and chloroplast sequences are in GenBank (Accessions: MH509220 – MH509381). RADseq data was generated for 26 pooled populations (6-10 individuals / population) using the SacI restriction enzyme and sequenced on an Illumina HiSeq 2500. Chloroplast sequences were generated using Sanger sequencing for up to three individuals per 37 populations. Chloroplast sequences were aligned using CodonCode Aligner and proofread by hand. RADseq sequences were first screened using Stacks for SNPs that varied between populations but were fixed within populations, because we sequenced pooled data. These retained reads were than concatenated into one sequence by population and aligned.

Usage Notes

If others wish to perform their own alignments, the individual reads are available on NCBI (Accessions MH509220 – MH509381).

Funding

National Science Foundation, Award: DEB-1457686