POTGIETER, K*, J ROVA, E WALLANDER, V.A ALBERT, AND L STRUWE. Molecular & Integrative Physiology, University of Illinois, Urbana, IL 61801. - Large molecular trnL intron phylogeny of the Gentianales.
This trnL intron derived phylogeny of the Gentianales represents the
most extensive and most evenly sampled study of the group, or any
angiosperm order for that matter, to date. Past systematic work using
morphological and/or molecular sequence data did not effectively
resolve interfamilial relationships within the Gentianales. Increased
taxon sampling may effectively distribute phylogenetic signal more
evenly and thereby improve resolution of the major families at all
levels within the order. Roughly 500 accessions were sampled from
major tribes of the Strychnaceae, Loganiaceae, Gelsemiaceae,
Gentianaceae, Apocynaceae s.l., and Rubiaceae. Members of the
Oleaceae, Scrophulariaceae, and more distally related genera were
included as outgroups. Apocynaceae s.l. comes out in the most derived
position and has a sister group relationship with a clade consisting
of Strychnaceae-tribe Strychneae and Loganiaceae s.str. Gelsemiaceae
is supported as a distinct family and is unresolved along with
Strychnaceae-tribe Antonieae and Rubiaceae. Surprisingly,
Gentianaceae is in the basalmost position; it is also the only family
(except for tribes Antonieae and Spigelieae in the Strychnaceae) that
lack alkaloids. Most of the traditional families in the Gentianales
appear to be monophyletic, except for Strychnaceae and Loganiaceae.
Key words: Apocynaceae s.l., Gelsemiaceae, Gentianaceae, Gentianales, Loganiaceae, phylogeny, Rubiaceae, Strychnaceae, trnL intron