BROUILLET, LUC1*, GERALDINE A. ALLEN2, JOHN C. SEMPLE3, and MOTOMI ITO4. 1Herbier Marie-Victorin, IRBV, Universite de Montreal, 4101 Sherbrooke St. E, Montreal, QC, Canada, H1X 2B2; 2Department of Biology, University of Victoria, P.O. Box 3020 STN CSC, Victoria, British Columbia, Canada, V8W 3N5; 3Department of Biology, University of Waterloo, Waterloo, ON, Canada, N2L 3G1; 4Department of Systems Sciences (Biology), University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902, Japan. - ITS phylogeny of North American asters (Asteraceae : Astereae).
Genus Aster s.l. has been the object of much controversy, particularly
in North America (NA). Recently, splitting the aggregate genus has
been suggested, notably in the thorough morphological review of Nesom
(1994, 2000), but students of the group have yet to agree on
delimitation and relationships of the segregate taxa. Also,
relationships with Eurasian taxa, and among them, have been
controversial. Recent ITS phylogenetic analyses by Morgan (1997) and
Noyes (2000, & Rieseberg 1998) provide a framework to test hypotheses
of relationships among members of the Aster complex. In this
phylogenetic analysis, we are adding more than 60 ITS sequences of
many critical taxa representing all major lineages that have been
recognized within Aster s.l., in order to intensify taxon sampling
both within and among groups in the NA Astereae and in Eurasian Aster.
All North American and derivative taxa form a monophyletic clade,
while Eurasian taxa also form a single clade excluding all NA taxa.
Thus, we confirm that Aster is polyphyletic; the name should be
applied only within subtribe Asterinae (Eurasian clade); Doellingeria
is strictly North American and not disjunct with east Asia. Each major
clade of NA Astereae have an aster segregate at its base: Eucephalus
and Doellingeria are basal to all NA Astereae; Sericocarpus is sister
to the Solidago lineage within Solidagininae; the Symphyotrichinae
(all asters) are sister to Machaerantherinae, where Eurybia and
Oreostemma are basal; Ionactis and Oclemena are sister to the
Conyzinae-Chrysopsidinae clade. Within the Symphyotrichinae,
Canadanthus, Ampelaster and A. chapmanii form a grade basal to
Symphyotrichum (including Psilactis). Biogeographically and
ecologically, it appears that on both sides of North America,
temperate, mesic taxa have developed first, followed by multiple
radiations into more xeric habitats.
Key words: Aster s.l., Asteraceae, Astereae, Biogeography, ITS, Molecular phylogeny