Systematic studies on mexican coreopsis (compositae). Coreopsis mutica: Flavonoid chemistry, chromosome numbers, morphology, and hybridization

Abstract

Coreopsis mutica is a highly variable species occurring in the highlands from Central Mexico southeastward barely into El Salvador and Honduras. It is not continuous over this range, however, but is found in three geographic population centers: one in Guatemala and Chiapas, a second in Oaxaca, and the third in Central Mexico. Populations in Guatemala and Chiapas are uniform in chromosome number (2n = 56), leaf flavonoid chemistry, and morphology. Var.microcephala is proposed to accommodate these assemblages. Plants comprising populations centered around Cd. Oaxaca have a chromosome number of 2n = ca. 112. This large complex consists of two distinct varieties and their putative hybrids. Those plants to the northwest of Cd. Oaxaca (var.subvillosa) are constant in leaf flavonoid chemistry (producing only flavones) and possess a combination of distinctive morphological traits. To the southeast of Cd. Oaxaca plants invariably contain flavonols and anthochlors in their leaves in addition to flavones. Moreover, these plants (the newly proposed var.carnosijolia) are readily separable from var.subvillosa by a number of morphological features. Evidence is presented that the two taxa hybridize in the vicinity of Cd. Oaxaca. On the southeastern edge of the var.subvittosavar. carnosifolia complex a population was encountered which has a chromosome number of 2n = 56 and a very distinctive morphology and flavonoid chemistry. These plants have been accorded taxonomic status as var.multiligulata. Two morphologically similar, yet distinguishable, varieties occur in Central Mexico. It has been determined that the two differ also in chromosome number and leaf flavonoid chemistry. One taxon (var.leptomera) has a chromosome complement of 2n = 56 and produces only flavones in its leaves, whereas var.mutica has a chromosome number of 2n = ca. 112 and produces flavones, flavonols, and anthochlors.