Molecular phylogeny of Daucus (Apiaceae): Evidence from nuclear ribosomal DNA ITS sequences

Abstract

The genus Daucus L. (Apiaceae Lindl.) is defined morphologically by a suite of easily observed and well-known characters, including dorsally compressed mericarps, hairs on primary ridges, and singly arranged spines on the secondary ridges of the fruit (Okeke, 1978). The genus is mainly distributed in Europe including the Mediterranean regions, southwestern and central Asia, and tropical Africa. A few species are also found in the other continents; D. glochidiatus (Labill.) Fischer & C.A. Mey. is restricted to Australia and New Zealand, D. montanus Humb. & Bonpl. ex Spreng. to central and South America, and D. pusillus Michx. to North and South America (Heywood, 1983). The genus is economically important; it includes the common carrot, Daucus carota L. ssp. sativus (Hoffm.) Arcang., a root crop which is widely cultivated in most parts of the world. The carrot is medicinally important as stimulant, deobstruent, and excitant and also valuable for other urinary problems, skin affliction, jaundice, dropsy, and uterine ailments (Heywood, 1978; Okeke, 1978). Taxonomically, Daucus and other spiny-fruited genera (e.g., Caucalis L., Torilis Adans., and Orlaya Hoffm.) were treated into tribe Caucalideae Tausch on the basis of the unique presence of spines, hooks, tubercles, or bristly hairs on the primary and/or secondary ridges of their fruits (Bentham and Hooker, 1867). This is in contrast to Drude (1898), who distributed these spiny-fruited plants into tribe Dauceae and tribe Scandiceae subtribe Caucalidinae. Drude believed that members of Dauceae were allied to plants in his tribe Laserpitieae, whose members have fruits without spines but with primary and prominent secondary ridges. Koso-Poljansky (1916; 1917), following Drude’s segregation of the spiny-fruited umbles into Dauceae and Caucalidinae, expanded tribe Dauceae including many representatives of Drude’s Laserpitieae. However, all the spiny-fruited taxa (e.g., Drude’s Dauceae and Scandiceae subtribe Caucalidinae) were united as a single tribe Caucalideae on the basis of phytochemistry and micro-characters of fruits using scanning electron microscopy (Heywood and Jury in Heywood, 1982) whereas the tribe Laserpitieae was retained as an independent tribe (Heywood, 1978). Infrageneric classification of Daucus L. largely based on anatomical and morphological features of the mature fruit has been also controversial. The genus Daucus were variously divided into sections, subgenera, or some species of the genus were even treated into separated genera, Journal of Species Research 3(1):39-52, 2014