Potential utility of chloroplast trnL (UAA) gene intron sequences for inferring phylogeny in Scrophulariaceae
Whereas chloroplast DNA-derived sequence data from protein coding regions have been utilized successfully at many taxonomic levels in recent years, sequences which are variable enough to allow for efficient phylogenetic inference (maximum information with relatively low sequencing costs and effort) at the subfamilial level huve been few. Sequence data were obtained in this study from a noncoding region, the trnL (UAA) gene intron, from a selection of taxa from the Scrophulariaceae and closely related families (representing 41 species in 26 genera). Groups of species from commonly recognized tribes and subtribes were included to determine if these taxa were grouped together by analyses of this sequence. These included seven species from the tribe Cheloneae. 14 species of the tribe Antirrhineae, and four from the tribe Euphraseae or Pediculareae, Also included are representatives of Bignoniaceae (four species, each in a different genus ), and the outgroup Anisacanthus thurberi of the Acanthaceae. These taxa were examined to estimate the potential utility of this sequence data set for subfamilial phylogenetic reconstruction. In the majority rule consensus tree, taxa of the tribe Cheloneae (the North American representatives) form a monophyletic clade and generally conform to previous systematic hypotheses from the literature. Sampled taxa of the tribe Antirrhineae (with the exception of Linaria) also appear as a potentially monophyletic clade, with support for the subtribes Antirrhinae and Maurandynae. Based on these sequence data wc recommend reassessment o f some generic placements at the tribal level. The genera Verbascum and Scrophularia appear on the same, well-supported clade and Veronica and Digitalis occur together on another well-supported clade. The trnL intron sequence comparisons indicate that this relatively short region (about 500 bp) may be useful in studies of phylogeny within Scrophulariaceae and allied taxa at the suprageneric level.