Coreopsideae is a tribe of flowering plants belonging to the Asteroideae subfamily.[1] It includes widely cultivated genera such as Cosmos and Dahlia.
A similar group has been recognized since 1829, generally as part of the tribe Heliantheae (Cassini, 1819).[2] In the late 20th century, molecular studies caused a slightly redefined version of this group to be recognized as its own tribe, Coreopsideae.[2] The larger version of Heliantheae was split into tribes including Bahieae, Chaenactideae, Coreopsideae, Helenieae and, finally, Heliantheae (sensu stricto).[3] Within the tribe, the traditional definition of genera based on flower and fruit characters does not reflect evolutionary relationships as inferred through molecular phylogenetics.[4]
The tribe is characterized by shiny green bracts at the base of the flower head in two rows: an inner row of tightly spaced bracts and an outer row of a smaller number pointing downward.[5] It includes five genera that use C4 carbon fixation: Chrysanthellum, Eryngiophyllum, Glossocardia (including Guerreroia), Isostigma, and Neuractis. These genera are thought to share a common ancestor and thus a single origin of C4 carbon fixation.[6]