NrDNA external transcribed spacer (ETS) sequence data, reticulate evolution, and the systematics of Machaeranthera (Asteraceae)

Abstract

Abstract Sequence data from the nrDNA external transcribed spacer (ETS) were generated to help resolve questions about the evolution of Machaeranthera left unanswered by previous analyses of chloroplast DNA (cpDNA) restriction site data and nrDNA ITS sequence data. Combined ITS and ETS (nrDNA) evidence agreed with cpDNA evidence in supporting a close relationship between Oonopsis and M. tanacetifolia. Nuclear rDNA evidence also supported an alliance between M. sections Blepharodon and Sideranthus. The nrDNA evidence provided greater support for the relationships of M. gypsitherma, M. heterophylla, M. stenoloba, and M. viscida than earlier analyses of ITS sequence data, reinforcing earlier conclusions that these species have experienced reticulate evolution. Finally, nrDNA evidence provided strong support for a group consisting of M. bigelovii, M. canescens, M. gypsitherma, and M. riparia. The relationships that nrDNA evidence supported for these four species conflicted substantially with those supported b...