Macromorphological and cytogenetic analysis of the genus Cosmos (Asteraceae, Coreopsideae), with a key for identification [Análisis macromorfológico y citogenético del género cosmos (Asteraceae, Coreopsideae), con una clave para su identificación]

Abstract

The genus Cosmos is restricted to the Americas, and Mexico represents its center of diversifi cation. Some species have a wide distribution and have been intensively collected, whereas others, due to their narrow distribution, are poorly known. This has generated a poor understanding of its morphological variability and infrageneric and interspecifi c limits, as well as confusion at the intergeneric level within tribe Coreopsideae. Polyploidy and aneuploidy have played an important role in the speciation of the group. The ploidy level variation can be seen between species, as well as in populations of the same species. Macromorphological data are used to support recognition of intergeneric limits, infrageneric groups, and species. Evidence of chromosome number variability and geographic distribution information for Cosmos is also included. These data are fundamental for the taxonomic understanding of the genus. A key for the identifi cation of all species of Cosmos is provided.