Asters An Overview

John C. Semple WAT

An Overview of "Asters"

Flowering plants commonly known as "asters" are members of more than a dozen genera in the tribe Astereae of the Sunflower family. Asters of all sorts occur throughout North America and across northern and central Eurasia, with a few species in South America. There are estimated to be 250-300 species worldwide; more than half of them are native to Canada and/or the United States. Traditional treatments place most asters in the genus Aster L. However, during the last decade analyses of morphology, chloroplast DNA restriction fragment length polymorphisms and ITS sequence data, and on going karyotype studies have all demonstrated that asters are polyphyletic and members of a number of very distinct phylads within the tribe (Nesom 1994 and numerous cited papers); Lane et al. 1996; Xiang and Semple 1996; Noyes and Rieseberg 1999; Brouillet et al. 2001; Semple et al. 2001). Asters can be divided into two categories following the general phylogeny of the entire tribe: (I) "asters" related to genera native to South America, Africa and Asian, and (II) "asters" of the North American clade of the tribe.

The presentation here represents a significant shift in my position regarding generic limits to one that I believe will be the "new standard taxonomy" of asters. There really is no satisfactory compromise between the desire to maintain Aster as a large broadly defined genus with as many species as possible and the need to recognize that the traditional very broad concept of the genus is not monophyletic and not based on synapomorphies (shared derived traits). The treatment of asters in Semple et al. (1996) was an attempt at an acknowledged compromise between the old and new classifications and as such is inconsistent with the most recent data.. Most significant is that the molecular evidence strongly shows that there are no true asters in North America (members of the genus Aster) with one exception the arctic-alpine Aster culminis and that majority of species placed in the genus by North American botanists belong in Eurybia Nees and Symphyotrichum Nees.

The generic treatments of North American asters proposed by Guy Nesom (1994) fit the new data quite well, although there are a number of species and a few groups of species that are not aligned in accordance with the molecular data. These are either realigned as indicated in this website or the continuing ambiguity about their phylogenetic position is discussed.

In the discussion below many of the genera cited are linked to additional pages at the this website presenting information on morphology, cytology and summaries of unresolved problems with phylogeny and classification. Numerous illustrations of individual species can be accessed from these additional pages.

The Tribe Astereae includes over 3000 species in nearly 200 genera. This website deals with only a small portion of these taxa.

I. South American and Old World Astereae

The first category of asters and many non-aster-like Astereae are found in South American, Africa and SE Asia and Australia with close relatives in Europe and Asia. The genus Aster in the new monophyletic sense (type species Aster amellus) is Eurasian and a member of this first category of Astereae. The genus includes species previously included in Diplactis and Kalimeris. The basal grade of phylads also includes some African and Eurasian "aster" and aster-like genera such as Bellis, Callistephus, Felicia, Galatella, Linosyris and Tripolium, which at one time or another have been included in Aster in the broadest polyphyletic sense. These all have a chromsome base number of x=9. Bremer (1994) hypothesized that the tribe had either paleotropical or North American origins. Semple (1995) incorrectly hypothesized that the tribe had its origins in Eurasia and that on the basis of RFLP cpDNA data genera such as Erigeron and Felicia were primitive members of the tribe, while Aster was North American and not primitive. Nesom (1994) proposed a southern hemisphere origin for the tribe, which is now likely the correct hypothesis. Long distance dispersal must account for the present distribution pattern of the tribe across the southern hemisphere and from southern hemisphere areas into northern hemisphere areas. Rather than the tribe migrating into the Southern Hemisphere, it appears to have migrated out of the Southern Hemisphere into Eurasian several times and into North America just once. Members of the North American clade much more recently migrated into Europe, Asia and South America (e.g., Erigeron and Solidago).

II. Asters of the North American Clade

The North American Clade of the tribe Astereae is well defined genetically (Noyes and Rieseberg 1999; Brouillet et al. 2001). It includes various kinds of asters, the goldenrods (Solidago), the grass-leaved goldenrods (Euthamia), fleabanes (Erigeron), goldenasters (Bradburia, Chrysopsis, Heterotheca, Pityopsis), many other genera of white, purple and yellow rayed flowering herbs and shrubs (e.g., Chrysothamnus, Petradoria, Machaeranthera, Xanthisma) and a number of rayless species.

The North American Clade also includes some 13 genera of "asters" which occur as basal members of several different main branches of the clade. These include Doellingeria, Eucephalus, Eurybia, Herrickia, Ionactis, Oclemena, Oreostemma, Sericocarpus and Subtribe Symphyotrichinae, which is divided on molecular and morphological grounds into Canadanthus, Ampelaster, Almutaster, Psilactis and Symphyotrichum (including Brachyactis and Virgulus). Brouillet et al. (2001) and Brouillet et al. (2004) included sufficient species to adequately resolve the phylogenetic position of each of these genera within the North American Clade. Previous studies lacked sufficient numbers of "asters" to achieve this, although members of some were included in DNA studies (Xiang and Semple 1996; Noyes and Rieseberg 1999). Nesom's studies (2000, 1996 and earlier) give an overview of the morphological limits of these native North American genera of asters with some modifications noted on this web site. Revised treatments of all of this aster genera are in press in Flora of North America. Vol. 20. Asteraceae, Part 2. Astereae and Senecioneae (Oxford University Press).

Publications on asters by John C. Semple

Semple, J.C. 1976. The karyotype of Aster ericoides L. (Asteraceae): some Canadian populations. Canad. J. Genet. Cytol. 18: 661-664.

Semple, J.C. 1978. The cytogeogrpahy of Aster pilosus (Compositae-Astereae): Ontario and the adjacent United States. Canad. J. Bot. 56: 1274-1279.

Semple, J.C. 1979. The cytogeography of Aster lanceolatus (synonyms A. simplex and A. paniculatus) in Ontario with additional counts from populations in the United States. Canad. J. Bot. 57: 397-402.

Semple, J.C. and L. Brouillet. 1980a. A synopsis of North American asters: the subgenera, sections and subsections of Aster and Lasallea. Amer. J. Bot. 1010-1026.

Semple, J.C. and L. Brouillet. 1980b. Chromosome numbers and satellite chromosome morphology in Aster and Lasallea. Amer. J. Bot. 67: 1027-1039.

Semple, J.C. and J. Ford. 1981. The phytogeography of leaf morphology in two species of North American asters: Lasallea novae-angliae and L. oblongifolia (Compositae). Brittonia 35: 517-522. [Lasallea = Virgulus]

Semple, J.C. 1982. Observations on the morphology and cytology of Aster hemisphaericus, A. paludosus and A. chapmanii with comments on the chromosomal base number and phylogeny of Aster subg. Aster sect. Heleastrum. Syst. Bot. 7: 60-70.

Semple, J.C. and R. A. Brammall. 1982. Wild Aster lanceolatus × lateriflorus hybrids in Ontario and comments on the origin of A. ontarionis (Compositae: Astereae). Canad. J. Bot. 60: 1895-1906.

Semple, J.C. 1982b. Aster avitus in North Carolina. Castanea 47: 409-410.

Semple, J.C., J.G. Chmielewski, K. S. Rao & G. A. Allen. 1983. The cytogeography of Aster lanceolatus. II. A preliminary survey of the range including A. hesperius. Canad. J. Bot. 61: 434-441.

Chmielewski, J.G. and J.C. Semple. 1983. The cytogeography of Aster lanceolatus. III. Cytoecology in southern Ontario. Canad. J. Bot. 61: 1879-1886.

Semple, J.C., J.G. Chmielewskiand C.C. Chinnappa. 1983. Chromosome number determinations in Aster L. (Compositae with comments on cytogeography, phylogeny and chromosome morphology. Amer. J. Bot. 70: 1432-1443.

Semple, J.C. and J.G. Chmielewski. 1983. Treatment of Aster. In: G.W. Argus and D.J. White, eds. Atlas of the rare vascular plants of Ontario. Part 2. National Museums of Canada, Ottawa.

Semple, J.C. 1984. Cytogeographic studies on North American asters. I. range surveys of Virgulus adnatus, V. concolor, V. georgianus, V. grandiflorus, V. novae-angliae, V. ob- longifolius, V. patens, and V. walteri. Amer. J. Bot. 71: 522-531.

Semple, J.C. and J.G. Chmielewski. 1985. The cytogeography of Aster pilosus (Compositae- Astereae). II. Survey of the range, with notes on A. depauperatus, A. parviceps and A. porteri. Rhodora 87: 367-379.

Chmielewski, J.G. and J.C. Semple. 1985. Cytogeographic studies on North American asters. II. Virgulus ericoides and V. novae-angliae in southern Ontario. Canad. J. Bot. 63: 1652-1653.

Semple, J.C. 1985a. Chromosome number determinations in Fam. Compositae tribe Astereae. Rhodora 87: 517-527.

Semple, J.C. 1985b. New names and combinations in Astereae. Phytologia 58: 429-431.

Chmielewski, J.G. and J.C. Semple. 1985 [1984]. Significant range extension series: Aster praealtus var. praealtus new to Perth County. Ontario Field Biol. 38 [1984]: 37.

Semple, J.C. and J.G. Chmielewski. 1987a. A revision of the Aster lanceolatus Complex (Compositae: Astereae): a multivariate morphometric study. Canad. J. Bot. 65: 1046-1062.

Semple, J.C. and S. B. Heard. 1987. The asters of Ontario: Aster L. and Virgulus Raf. (Compositae: Astereae). Univ. Waterloo Biol. Ser. 30: 1-88.

Semple, J.C. and J.G. Chmielewski. 1987b. Chromosome numbers in Fam. Compositae, Tribe Astereae. II. Additional Counts. Rhodora 89: 319-325.

Semple, J.C. and J. G. Chmielewski, and M. Lane. 1989. Chromosome numbers in Fam. Compositae, Tribe Astereae. III. Additional counts and comments on some generic limits and ancestral base numbers. Rhodora 91: 296-314.

Chmielewski, J.G., and J.C. Semple. 1989. The cytogeography of Aster pilosus var. pilosus in southern Ontario revisited. Canad. J. Bot. 67: 3517-3519.

Semple, J.C. and J.G. Chmielewski. 1991. A multivariate morphometric study and revision of Aster subg. Doellingeria sect. Triplopappus (Compositae: Astereae). Canad. J. Bot. 69: 256-276.

Semple, J.C. 1992. A geographic summary of chromosome number reports for North American asters and goldenrods (Compositae: Astereae). Ann. Missouri Bot. Garden 79: 95-109. [Based on invited paper presented at the W.H. Lewis Tribute Symposium, St. Louis, 7 Oct 1990]

Semple, J.C., Jie Zhang and ChunSheng Xiang. 1993. Chromosome numbers in Fam. Compositae, Tribe Astereae. V. Eastern North American taxa. Rhodora 95: 234-253.

Semple, J.C. 1995. A review of hypotheses on ancestral chromosomal base numbers in the tribe Astereae and the genus Aster. In D.J.N. Hind, C. Jeffrey and G.V. Pope, eds. Advances in Compositae Systematics. pp.153-165. Royal Botanic Gardens, Kew.

Xiang, ChunSheng and J.C. Semple. 1996. Molecular systematic study of Aster sensu lato and related genera (Asteraceae: Astereae) based on chloroplast DNA restriction site analyses and mainly North American taxa.. In D.J.N. Hind (Editor-in-Chief). Proceeding of the International Compositae Conference, Kew, 1994. Vol. 1. Systematics (vol. eds D.J.N. Hind and H. Beentje). pp. 393-423. Royal Botanic Gardens, Kew.

Semple, J.C., S. Heard and ChunSheng Xiang. 1996. The Asters of Ontario (Compositae: Astereae): Diplactis Raf., Oclemena Greene, Doellingeria Nees and Aster L. (including Canadanthus Nesom, Symphyotrichum Nees and Virgulus Raf.). U. Waterloo Biol. Series 38: 1-94.

Semple, J.C., ChunSheng Xiang, Jie Zhang, M. Horsburgh and R. Cook. 2001. Chromosome number determinations in Fam. Compositae, Tribe Astereae. VI. Western North American taxa and comments on generic treatments of North American asters. Rhodora 103: 202-218.

ALLEN, G.A.*, BROUILLET, L., SEMPLE, J.C. 2001. A molecular phylogeny of the Eucephalus asters (Asteraceae) based on ITS sequences, with biogeographic and morphological inferences. CBA/ABC Meeting, Kelowna, BC, June 2001.

BROUILLET, L.*, ALLEN, G. , SEMPLE, J.C., and ITO, M. 2001. ITS phylogeny of North American asters (Asteraceae: Astereae): basal grade to North American lineages and distinct from Eurasian ones. CBA/ABC Meeting, Kelowna, BC, June 2001.

BROUILLET, L.*, G. A. ALLEN, J. C. SEMPLE, and M. ITO. 2001. ITS phylogeny of North American asters (Asteraceae : Astereae). Botany 2001 [ASPT/BSA/IOPB joint meeting] Albuquerque, New Mexico 12-16 August 2001.

Chmielewski, J.G., and J.C. Semple. 2001. The Biology of Canadian weeds. 113. Symphyotrichum lanceolatum (Willd.) Nesom [Aster lanceolatus Willd.] and S. lateriflorum (L.) Löve & Löve [Aster lateriflorum (L.) Britt.]. Canad. J. Plant Sciences 81: 829-849.

Chmielewski, J.G., and J.C. Semple. 2001. The Biology of Canadian weeds. 114. Symphyotrichum pilosum (Willd.) Nesom (Aster pilosus Willd.). Canad. J. Plant Sciences 81: 851-865.

Semple, J.C., S.B. Heard and L. Brouillet. 2002. Cultivated and native asters of Ontario (Compositae: Astereae): Aster L. (including Asteromoea Blume, Diplactis Raf. and Kalimeris (Cass.) Cass.), Callistephus Cass., Galatella Cass., Doellingeria Nees, Oclemena E.L. Greene, Eurybia (Cass.) S.F. Gray, Canadanthus Nesom, and Symphyotrichum Nees (including Virgulus Raf.). U. Waterloo. Biol. Series No. 41: 1-134. [abstract]

Chmielewski, J.G., and J.C. Semple. 2003. The biology of Canadian weeds. 125. Symphyotrichum ericoides (L.) Nesom (Aster ericoides L.) and S. novae-angliae (L.) Nesom (A. novae-angliae L.). Canad. J. Plant Sciences 83: 1017-1037.

Semple, J.C., and R.E. Cook. 2004. Chromosome numbers in Fam. Compositae, Tribe Astereae. VII. Some eastern North American and Eurasian taxa. Rhodora 106: 253-272.

Semple, J.C. 2004. Miscellaneous nomenclatural changes in Astereae (Asteraceae). Sida 21(2): 759-765.

Leonard, M.R, R.E. Cook and J.C. Semple. 2005. A multivariate morphometric study of the aster genus Sericocarpus Nees (Asteraceae: Astereae). Sida 21: 1471-1505.

Semple, J.C. and J.L.A. Hood. 2005. Pappus variation in North American Asters. I. Double, triple and quadruple pappus in Symphyotrichum and related aster genera (Asteraceae: Astereae). Sida 21: 2141-2159.

Semple, J.C. and J. G. Chmielewski. 2006. Doellingeria Nees. pp. 43-46. In Flora North America Editorial Committee, eds. Flora of North America. Vol. 20. Asteraceae, Part. 2. Astereae and Senecioneae. Oxford University Press.

Semple, J.C. and M.R. Leonard. 2006. Sericocarpus Nees. pp. 101-105. In Flora North America Editorial Committee, eds. Flora of North America. Vol. 20. Asteraceae, Part 2. Astereae and Senecioneae. Oxford University Press, New York.

Semple, J.C. 2006. Ampelaster Nesom. pp. 460. In Flora North America Editorial Committee, eds. Flora of North America. Vol. 20. Asteraceae, Part 2. Astereae and Senecioneae. Oxford University Press.

Brouillet, L., J.C. Semple, G.A. Allen, K. Chambers and S. Sundberg. 2006. Symphyotrichum Nees pp. 465-539. In Flora North America Editorial Committee, eds. Flora of North America. Vol. 20. Asteraceae, Part 2. Astereae and Senecioneae. Oxford University Press.

Brouillet, L., T. Lowrey, L. Urbatsch, V. Karaman-Castro, G. Sancho, S. Wagstaff, and J.C. Semple. 2008, in press. Chapter 37. Phylogeny and evolution of the Astereae (Compositae or Asteraceae). Pp. 449-490. In Systematics, Evolution and Biogeography of the Compositae, Funk, V.A., A. Susanna, T. Stuessy, and R. Bayer (eds.). IAPT, Vienna, Austria.