PREMISE OF THE STUDY: Although our awareness of ploidy diversity has expanded with the application of flow cytometry, we still know little about the extent to which cytotypes within mixed-ploidy populations are genetically differentiated across environmental gradients. METHODS: To address this issue, we reared 14 populations of Solidago altissima spanning the prairie–forest ecotone in Minnesota in a common garden with a watering treatment. We assessed ploidy frequencies and measured survival, flowering phenology, and plant architectural traits for 4 years. KEY RESULTS: All populations harbored multiple cytotypes; prairie populations were dominated by tetraploids, forest populations by hexaploids. Diploids and polyploids differed significantly for 84% of the traits. Beyond average differences, the slope of trait values covaried with latitude and longitude, but this relationship was stronger for diploids than the other two polyploid cytotypes as indicated by numerous ploidy × latitude and ploidy × longitude interactions. For example, the timing of flowering of the cytotypes overlapped in populations sampled from the northeastern hemiboreal forest but differed significantly between cytotypes sampled from populations in the southwestern prairie. The watering treatments had weak effects, and there were no ploidy differences for phenotypic plasticity. CONCLUSIONS: Our data show that diploids have diverged genetically to a greater extent than polyploids along the environmental clines sampled in this study. Moreover, different environments favor phenotypic convergence over divergence among cytotypes for some traits. Differences in ploidy frequency and phenotypic divergence among cytotypes across gradients of temperature and precipitation are important considerations for restoration in an age of climate change.

Prairie_Forest_Precip_Gradient_DRYADThis file includes all original data related to the analysis published by the American Journal of Botany including: 1) The original radomized block design, 2) the rearranged split-plot block design, 3) the population code as it appears in the manuscript, 4) a genotype number, 5) the watering treatment (D=dry; W = wet), 6) Biome (P=prairie, F=forest), 7) latitude and longitude of wild population, 8) flow cytometry peaks and pg DNA calculation, 9) original rhizome weight at planting, and for each year 2007-2010 when measured, 10) date of first flower, 11) leaf number, 12) height, 13) basal stem diameter, 14) abaxial and adaxial stomatal counts and their ratio, 15) clone number, 16) branch number 17) dried biomass. Herbivory (yes/no) for 2008 is also included.