ITS phylogeny of Middle Asian geophilic Umbelliferae-Apioideae genera with comments on their morphology and utility of psbA-trnH sequences

摘要

Generic delimitation and relationships within the taxonomically controversial group of geophilic Umbelliferae from Middle Asia are problematic. Geophilic plants in arid regions have a short period of development during spring and early summer and survive unfavorable seasons due to the presence of tuber-like underground storage organs. To investigate the circumscription of recently recognized Middle Asian geophilic genera and their relationships, we conducted phylogenetic analyses using DNA sequence data from rapidly evolving nuclear (nrITS) and chloroplast (psbA-trnH intergenic spacer) regions as well as multivariate analyses of the morphological and ITS data. Our results show that Galagania and Mogoltavia are monophyletic, whereas Bunium, Hyalolaena and Oedibasis are polyphyletic. Elaeosticta, one of the larger genera of geophilic Middle Asian umbellifers, is rendered paraphyletic by the inclusion of the enigmatic Hyalolaena melanorrhiza. The genus Scaligeria, in which most species of Elaeosticta were initially described, is not grouped with these genera and has other affinities. Our analyses also show that the morphological characters used for the delimitation of genera within this group of Umbelliferae (such as life form, cotyledon number, presence/absence of petiolules of basal leaflets, shape of mericarp ribs, width of mericarp commissure, number of secretory ducts in mericarp furrows) are rather homoplastic. The psbA-trnH sequences were not informative enough to reveal relationships among the genera studied, although some interesting features in the spacer evolution were revealed (maximum reduction in length among Umbelliferae, homoplasious directed substitutions to restore secondary structure).