SCHILLING, EDWARD E.* and PATRICIA B. COX. Department of Botany, University of Tennessee, Knoxville, TN 37996-1100 U.S.A.. - Systematic analysis of Liatrinae (Asteraceae).
Phylogenetic analyses of DNA sequence data were undertaken to address
systematic questions involving subtribe Liatrinae. Molecular
phylogenetic results placed Liatrinae among the relatively derived
x = 10 lineage of Eupatorieae as sister to the
Eupatorium + Eupatoriadelphus clade. This result is in
agreement with biogeographic distributions (the two clades are unique
in Eupatorieae for their distributions centered in eastern North
America), although not with traditional taxonomic treatment. Molecular
results supported separation of Trilisa and Litrisa as
distinct from Carphephorus, and also provided confirming
evidence for placement of the anomalous Garberia and
Hartwrightia within Liatrinae. The shrubby Garberia is
placed basally as the sister group to the remainder of the otherwise
herbaceous subtribe. There is, however, incongruence in the placement
of Hartwrightia. Results based on the chloroplast encoded
matK placed it as sister to Carphephorus, whereas those
based on the nuclear ITS placed it with Trilisa. Combined
matK + ITS results for the entire subtribe gave little
resolution, but with Hartwrightia (and Litrisa, another
anomalous genus) removed, there was strong support for a sister group
relationship between Liatris and Carphephorus, with
Trilisa sister to that clade. Hartwrightia may thus be
an example of a morphologically distinct genus that has arisen through
phylogenetic reticulation.
Key words: Asteraceae, Eupatorieae, ITS, molecular phylogenetics, phylogenetic reticulation