Phylogenetic relationships of Pachycladon (Brassicaceae) species based on three nuclear and two chloroplast DNA markers

Abstract

Sequence data from three nuclear ribosomal and two chloroplast DNA markers were used to assess interspecific relationships in Pachycladon. Of the two chloroplast markers, the rbcL data show no parsimony‐informative nucleotide differences, whereas the trnL‐trnF has eight parsimony‐informative nucleotides. The three nrDNA markers ITS, FRIGIDA, and gapC all had variable sites. For FRIGIDA we were able to sequence only five species and these have nine parsimony‐informative sites. Sequencing of cloned ITS PCR products yielded several unique copies of ITS for most species, and 34 parsimony‐informative nucleotides. The network of these ITS copies shows much sharing of ITS types within two groups of species, firstly P. cheesemanii/P. exilis and secondly P. enysii/P. fastigiata/P. stellata. In gapC two distinct sequence types (copy A and copy B) were cloned and these have 92.1% sequence similarity. The gapC‐copy A and copy B sequence matrices contain three and four parsimony‐informative characters, respectively. Previous studies of nrDNA ITS, morphological, and Amplified Fragment Length Polymorphism data distinguished three groups of New Zealand Pachycladon. In this study, P. exilis/P. cheesemanii was the most frequently retrieved of these groups, occurring in the FRIGIDA, ITS, and trnL‐trnF networks. A second group comprising P. enysii, P. fastigiata, P. latisiliqua, and P. stellata was only partially retrieved in the trnL‐trnF, ITS, FRIGIDA, and gapC‐copy B networks. A third group identified from previous studies of P. novae‐zelandiae and P. wallii was not retrieved in any of the networks. Overall, the five networks are characterised by a star‐like pattern of radiation with little structure in the internal branches.