Phylogenetic Affinities Among and Within the Coneflower Genera (Asteraceae, Heliantheae), a Chloroplast DNA Analysis

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Abstract
For most of their taxonomic history the genera Dracopis, Echinacea, Ratibida, and Rudbeckia have been closely allied with one another. More recently an alternative classification scheme was proposed by Harold Robinson in which he established the subtribe Rudbeckiinae to accommodate three of the genera, Dracopis, Ratibida, and Rudbeckia. He placed Echinacea in subtribe Ecliptinae. To understand better the possible relationships among these and other genera, restriction site analysis of the chloroplast genome was undertaken. Employment of 22 enzymes resulted in detection of 643 restriction site mutations of which 249 were phylogenetically informative. Wagner parsimony generated 84 equally parsimonious trees. Bootstrap and decay analyses were used to explore the robustness of the resulting clades. Weighted parsimony analyses of the data set using weights ranging from 1.1:1.0 to 1.5:1.0 in favor of site gains generated very similar tree topologies. Chloroplast DNA data support Robinson's subtribal disposition of the coneflower genera. Among the genera of Ecliptinae investigated, two evolutionary lineages were supported. The lineage containing Echinacea includes Heliopsis, Helianthella, Eclipta, and Acmella. Wyethia, Balsamorhiza, Engelmannia, Berlandiera, and Silphium are in the sister lineage. Most species of Echinacea and Rudbeckia were included in the restriction site analyses. Within these genera, some species groups were strongly supported. Low levels of variation at the species level, however, precluded detailed phylogenetic inferences. Multiple samples within species in most cases show little chloroplast DNA variation.

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