The phylogenetic and taxonomic position of Lilaeopsis (Apiaceae), with notes on the applicability of ITS sequence data for phylogenetic reconstruction

The relationships of the genus Lilaeopsis Greene have been difficult to determine primarily due to its simple morphology with entire, linear to spathulate leaves, simple umbels and lack of carpophore. Consequently, the genus has been referred to both Hydrocotyloideae and Apioideae. DNA sequence data from different genes (rbcL and matK) and non-coding regions (rpoC1 intron and ITS) were explored in order to determine the phylogenetic relationships of Lilaeopsis. Separate and combined analyses of rpoC1 intron, rbcL and matK data give almost congruent results with respect to a clade including Lilaeopsis. The three species of Lilaeopsis included in the analyses form a monophyletic group within the Oenanthe clade and hence belong to the Apioideae. Presently, the Mexican genus Neogoezia Hemsl. is considered its most likely sister group. Optimisation alignment of the ITS sequence data results in widely different phylogenetic hypotheses, but on the basis of congruence tests, two very similar trees can be selected. These trees are, however, incongruent with the trees obtained from analyses of the chloroplast sequences. As alignment of the ITS sequences is problematic even within the Oenanthe clade, the reliability of phylogenies on the basis of ITS data of higher taxonomic levels in the Apiaceae is questioned. However, for phylogenetic analysis within Lilaeopsis ITS sequences may prove useful and unproblematic.