DOI: 10.5061/dryad.gqnk98smp
title: Variation in reproduction and gene flow between cytotypes in a polyploid complex: one size does not fit all

description: Whole-genome duplication is considered an important speciation mechanism
 in plants. However, its effect on reproductive isolation between higher
 cytotypes is not well understood. We used backcrosses between different
 ploidy levels and surveys of mixed-ploidy contact zones to determine how
 reproductive barriers differed with cytotype across a polyploid complex.
 We backcrossed F1 hybrids derived from 2X-4X and 4X-6X crosses in the
 Campanula rotundifolia autopolyploid complex, measured backcross fitness,
 and estimated backcross DNA cytotype. We then sampled four natural
 mixed-ploidy contact zones (two 2X-4X and two 4X-6X), estimated ploidy,
 and genotyped individuals across each contact zone. Reproductive success
 and capacity for gene flow was markedly lower for 2X-4X than 4X-6X
 hybrids. In fact, 3X hybrids could not backcross; all 2X-4X backcross
 progeny resulted from neotetraploid F1 hybrids. Further, no 3X individuals
 were found in 2X-4X contact zones, and 2X and 4X individuals were
 genetically distinct. By contrast, backcrosses of 5X hybrids were
 relatively successful, particularly when crossed to 6X individuals. In
 4X-6X contact zones, 5X individuals and aneuploids were common and all
 cytotypes were largely genetically similar and spatially intermixed. Taken
 together, these results provide strong evidence that reproduction is low
 between 2X and 4X cytotypes, primarily occurring via unreduced gamete
 production, but that reproduction and gene flow are ongoing between 4X and
 6X cytotypes. Further, it suggests whole genome duplication can result in
 speciation between diploids and polyploids, but is less likely to create
 reproductive barriers between different polyploid cytotypes, resulting in
 two fundamentally different potentials for speciation across polyploid
 complexes.
description: The datasets attached are locations of individual plants in four
 mixed-ploidy populations in Germany, the Czech Republic, the United
 Kingdom, and Canada. Latitude and longitude were recorded for each plant
 using a degrees and decimal minutes system. Locations were then converted
 into a Cartesian coordinate system by calculating distance in meters from
 the southernmost plant and from the easternmost plant to establish Y-axis
 and X-axis coordinates, respectively. In no population was the same plant
 both the southernmost and westernmost. Leaf tissue from each plant was
 then collected and dried in silica gel. Genome content was estimated using
 flow cytometry, which was then compared to external standards to calculate
 estimated ploidy level.
description: This dataset consists for four csv files, one for each of the
 four populations listed below. Each csv file contains four columns, and
 each row represents one individual. Columns are as follows: Plant ID,
 Longitudinal distance (east-west, in meters), Latitudinal distance
 (north-south, in meters), and estimated genome copy number. In some case,
 suspected aneuploids were present. These were recorded as either 4.5 or
 5.5. Populations: Cheddar Gorge,
 Cheddar, England - Tetraploid-Hexaploid contact zone
 Misery Bay Provincial Nature Reserve, Ontario, Canada -
 Tetraploid-Hexaploid contact zone Mittelndorf, Saxony,
 Germany - Diploid-Tetraploid contact zone Prague, Czech
 Republic - Diploid-Tetraploid contact zone