An extensive survey was done of the genome size in the germplasm available for Coreopsis, Phlox and Rudbeckia, to examine the pattern of cytotype variation within each species and determine the natural occurrence of polyploids in these plants.
Zale, P. and P. Jourdan (2015) Genome size and ploidy of Phlox paniculata and related germplasm in subsections Paniculatae and Phlox. J. Amer. Soc. Hort. Sci. 140:436-448.
Jourdan, P., P. Zale and S. Stieve (2015) Germplasm Characterization and Enhancement for Phlox, Rudbeckia and Coreopsis. Acta Hort 1104:349-355
Zale P, Robarts WH, Jourdan P (2016) Genome size and ploidy levels of creeping phlox and related germplasm of mat-forming taxa from eastern and western North America. Scientia Horticulturae 203: 53-61