In
1994, a study of asters world-wide indicated that the native Eurasian species
stand apart from the North American ones –– especially significant in this
interpretation were the larger size and more symmetrically shaped chromosomes
and the generally larger, 2-sided, glandular achenes of the Eurasian
species.
Because
the concept of the genus Aster is linked (by rules of scientific
nomenclature, ICBN) to a single
species –– Aster amellus, native to Europe and Asia –– the name Aster
is most appropriately associated with the Eurasian species, leaving the
approximately 180 North American species to find names within other
genera.
Among
the North American species, a number of distinct groups can be recognized ––
some of them have been known for a long time.
Each of these groups appears to have developed along its own
evolutionary line, and the 1994 study proposed that each of the North American
groups be recognized as a distinct genus.
By
far the largest number of the North American species transferred from Aster
to other genera are now in Symphyotrichum (about 90 species). Other North American genera where the ‘old’
asters are now located are Almutaster, Ampelaster, Aster, Canadanthus,
Chloracantha, Doellingeria, Eucephalus, Eurybia, Oclemena,
Oreostemma, and Sericocarpus.
Aster ptarmicoides has proved to be a white-rayed species
of Solidago (goldenrod).
Some
of these Latinized scientific names were ‘invented’ and published long ago and,
by the rules of nomenclature, must be used.
The ‘principle of priority’ establishes that the first name published in
a specified manner is the correct one. Symphyotrichum,
which displaces the more euphonious Aster in the majority of the species,
seems especially peculiar and tongue-twisting, and although it has almost never
been used until very recently, it was first proposed in 1832 and can’t be
denied its rightful place.
Only
two North American species remain in the genus Aster, as the genus is
now much more narrowly defined:
Aster alpinus –– a mountain species that crosses from Asia into
Alaska and grows sporadically along the Rocky Mountains through western Canada
into Colorado. The only native NA
species of Aster.
Aster tataricus –– a garden species native to northeastern Asia that
occasionally ‘escapes’ from cultivation in North American plantings. In states mostly east of the Mississippi
River.
In
retrospect, the very large genus long-recognized as Aster was identified
based on a unifying concept of little more than a rhizomatous, herbaceous,
perennial habit and numerous white to blue rays. This combination of features occurs in many distinct groups on
both sides of the Atlantic and Pacific and it’s clear now that the evolution of
Eurasian asters occurred independently of the American species.
DNA
study has confirmed the basic split between the American and Eurasian species
and also shown that the North American species groups are more closely related
to goldenrods (Solidago), fleabanes (Erigeron), Boltonia,
and other American genera than to Eurasian species of Aster. Various summaries and abstracts are
available in documentation of the DNA support of these hypotheses and further
reports are forthcoming, primarily from Dr. Luc Brouillet, Université de
Montreal, with his students and colleagues.
Even
the Eurasian species of Aster have been divided into smaller genera. Aster tripolium (the single species
of the genus Tripolium), Aster sedifolius and A. punctatus (with other species, the
genus Crinitaria) and Aster linosyris and A. oleifolius
(with other species, the genus Galatella) are related among themselves
and more closely related to Bellis, Bellium, and Bellidiastrum
(= Aster bellidiastrum) than to Aster in the strict sense. The strictly defined genus Aster is
now limited to A. amellus and about 180 other species native to Europe
and Asia, including many beautiful ones (e.g., A. ageratoides, A. diplostephioides, A. flaccidus, A. himalaicus, A. tataricus). Among the closest relatives of A. amellus are A. pyrenaeus and A. thomsonii.
POPULAR ACCOUNTS OF THE
NAME CHANGES IN ASTER
Robert Dorn. 2003. Asters
Retreat to Eurasia. Castilleja 22(2): 3.
Gardener’s
Notebook. 2004. Aster La Vista? The American Gardener, November-December, p.
46.
Vernon Harms. 2002.
Where have all
our asters gone? Blue Jay
60: 151–152.
Deborah
Lewis. 2006. An
Aster By Any Other Name...?: The Dismantling of the Genus Aster. Iowa Native Plant Society Newsletter, Vol. 12, Issue 3, October.
Alan
Weakley. 2004. The Curious Case of the
Disappearing Asters. North
Carolina Botanical Garden Newsletter, March-April, p. 9.
Arthur Haines.
2001. Clarifying the
generic concepts of Aster sensu lato in New England. Botanical Notes 7: 1–7.
John Semple. 2009.
An Overview of “Asters.”
Semple’s web site, Univ. of
Waterloo, Ontario, Canada.
An excellent, easy-to-read introduction to the whole group of plants, including lots of good photos.
George
Yatskievych. 2004 (2005). How faster to master the Aster
disaster: a primer on the changing nomenclature of Missouri asters. Missouriensis 25: 26–32.
Brouillet, L., T. Lowrey, L.
Urbatsch, V. Karaman-Castro, G. Sancho, S. Wagstaff, and J.C. Semple. 2009.
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.
Greuter, W. 2003. The Euro+Med treatment of Astereae (Compositae) –– generic
concepts and required new names. Willdenowia 33: 45–47.
A synonymic
survey of Astereae genera accepted for the purpose of the Euro+Med
Project is presented.
As a
consequence of shifts in generic circumscription, or reassessment of accepted
specific and
subspecific
taxa, combinations that are required in the genera Erigeron, Eurybia,
Galatella,
Symphyotrichum
and Tripolium, but do not so far exist, are
validated. In one case (Erigeron alpinus
subsp.
intermedius) the validity of a previous combination, even though it was
rather irregularly proposed,
is confirmed.
Nesom, G.L. 1994.
Taxonomic overview of
Aster sensu lato (Asteraceae: Astereae), emphasizing the New World species. Phytologia 77: 141–297.
The original publication
providing detailed explanations of why North American Aster was split
into the various segregate genera as well as the formalities for making the
nomenclatural transfers from Aster to the segregates.
Nesom, G.L. 1995.
Key to the American genera
of Asterinae (Asteraceae).
Phytologia 79: 281–285.
Includes an identification “key” to the North
American genera segregated from Aster.
Nesom, G.L. 2000. Generic
conspectus of the tribe Astereae (Asteraceae) in North America and Central
America, the Antilles, and Hawaii.
Sida Misc. 20: 1–100.
Semple, J.C. et al. 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.
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., Doelleringia Nees,
Oclemena E.L. Greene, Eurybia (Cass.) S.F. Gray, Canadanthus Nesom,
and Symphyotrichum Nees (including Virgulus Raf.). Univ. Waterloo Biol. Ser. 41: i–viii, 1–135.
Various authors [Geraldine Allen, Luc Brouillet, Ken Chambers, Jerry
Chmielewski, Michelle Leonard, Guy Nesom, John Semple, Scott Sundberg]. 2006.
Astereae
(including aster segregates Almutaster, Ampelaster, Aster,
Canadanthus, Chloracantha, Doellingeria, Eucephalus,
Eurybia, Oclemena, Oreostemma, Sericocarpus, Symphyotrichum). Flora of North America, North of
Mexico. Vol. 20.
The link here goes to the genus Aster
(2 species) in Volume 20 –– each of the segregate genera is treated separately
in the same volume.
John Semple’s web site.
2009. Summary of
the phylogeny of the Tribe Astereae based on ITS gene sequence data. Univ.
of Waterloo, Ontario, Canada.
The cladogram shows that
‘asters’ have multiple evolutionary origins.
Allen, G.A., L. Brouillet, and J.C.
Semple. 2001. A
molecular phylogeny of the Eucephalus asters (Asteraceae) based on ITS
sequences, with biogeographic and morphological inferences. Abstract.
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). Abstract.
Botany 2001, August 2001. Albuquerque, N.M.
Brouillet,
L., G.L. Nesom, A.A. Anderberg, T.K. Lowrey, and L.E. Urbatsch. 2009.
Welwitschiella is a member of the African subtribe
Grangeinae (Asteraceae Astereae): a new phylogenetic position based on ndhF and
ITS sequence data. Kew Bull. 64(4):
1–16. Online, Dec 2009.
Fiz, O., V. Valcárcel, and P. Vargas. 2002.
Phylogenetic position of Mediterranean Astereae
and character evolution of daisies (Bellis, Asteraceae) inferred from
nrDNA ITS sequences. Molec.
Phylogenet. Evol. 25: 157–171.
Noyes, R.D. & L.H. Rieseberg. 1999.
ITS sequence data support a single origin for
North American Astereae (Asteraceae) and reflect deep geographic divisions in Aster
s.l. Amer. J. Bot. 86: 398–412.
Selliah, S. and L.
Brouillet. 2008. Molecular phylogeny
of the North American eurybioid asters (Asteraceae, Astereae) based on the
nuclear ribosomal internal and external transcribed spacers. Canad. J. Bot. 86: 901–915.
Vaezi, J. and L. Brouillet.
2009. Phylogenetic
relationships among diploid species of Symphyotrichum (Asteraceae:
Astereae) based on two nuclear markers, ITS and GAPDH. Molec. Phylogenetics Evol. 51: 540–553.
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Guy Nesom
Updated 1 Jan 2010