A biosystematic study of Coreopsis tinctoria and C. cardaminefolia (Compositae)

Abstract

This paper presents evidence which leads the authors to propose the reduction ofCoreopsis cardaminefolia (DC.) Nutt. to synonymy underC. tinctoria Nutt.Coreopsis cardaminejolia andC. tinctoria overlap morphologically in all characters measured, except for winging vs. non-winging of the achenes. The winging character is shown to be dependent upon segregation at one or two loci. Both “species” have chromosome numbers of 2n = 24 and 2n = 26. The basic number isx = 12, with some plants showing a supernumerary pair of chromosomes, which apparently undergo post-meiotic preferential distribution on both the maternal and paternal sides. The two taxa overlap extensively in range and occupy the same habitat, rather commonly occurring in mixed colonies.Coreopsis tinctoria is redefined to include the intrapopulational variation heretofore designatedC. cardaminefolia.