Families of Vascular Plants - EEB337H

Asterales - Asteraceae ("Compositae")


HelianthTAD01.jpg (81150 bytes)

1528 genera, 22,750 spp., worldwide; mainly herbaceous, but some are woody.  Flowers in dense, pseudanthial heads (capitula), the common receptacle of these surrounded by an involucre of bracts; bisexual, or some female, sterile, or functionally male.  Flowers epigynous and all tubular and regular, or just the central ones (disk flowers), the marginal ones (ray flowers) irregular with strap-like (ligulate) corollas, or all flowers with either ligulate or bilabiate corollas.

Judd et al. 1999, pp. 396-401.

Please bear with me while I go get this file...

A synapomorphy for the Asteraceae (excluding the Barnadesieae) is a 22 kb inversion in the chloroplast genome (shown in color; LSC, large single-copy region; SSC, small single-copy region; IR, inverted repeat; trnX, tRNA genes).

chloroplast genome, after Downie & Palmer 1992

 

Rudbeckia hirta (Heliantheae) is illustrated below as an example of some of the morphological features that characterize the family (Br, floral bract; G, inferior ovary; C, tip of corolla tube; A, tip of staminal tube; St, lobe of stigma; at right, the staminal tube split and unrolled - note the free filaments).

K (pappus) developing only on fruit or absent, of hairs, bristles, awns, or scales.   C(5).  A5, inserted on C, filaments usually free but anthers united in a ring (syngenesious).  G(2), with a single locule containing a single ovule. The fruit is an achene-like cypsela1. PBAsterfl181.jpg (14499 bytes)

PBAsterinfl400.jpg (18967 bytes)

Disk flowers with tubular C, hermaphrodite or male.

Ray (marginal) flowers with ligulate C, sterile or female.

Flowers with bilabiate (2+3, 4+1) C also formed.

Heterogamous capitula with both disk and ray flowers; homogamous capitula with exclusively one or the other.

 

Capitula can usefully be classified further by referring to the morphology of the flowers they contain, as has been done in the ROM Field Guide to Wildflowers... (p. 144), namely as

  • discoid, i.e. a homogamous head containing only disk flowers (e.g. most Cardueae);
  • ligulate, i.e. a homogamous head containing only ray flowers (e.g. most Lactuceae);
  • radiate, i.e. a heterogamous head in which ray flowers are present around the periphery of the capitulum, and disk flowers occupy the center of the capitulum, as in the Heliantheae (see the illustration of Helianthus at the top of this page).

 

Ontario native and naturalized genera of Asteraceae include the following:  Arctium, Bidens, Cichorium, Galinsoga, Helianthus (also illustrated above), Rudbeckia, Silphium, Solidago, Symphyotrichum (=Aster), Taraxacum, and Tragopogon. Lactuca sativa is lettuce.

1. Cypsela - a single-seeded, dry, indehiscent fruit that develops from an inferior ovary that in turn developed from two gynoecial primordia (hence the two branches of the stigma in the flower). It is achene-like in that the ovary wall is not joined to the seed coat of the enclosed seed.

Tribal classification after Mabberley (1997, 2008); compare with Judd et al. (2008; Table 9.4 - note synapomorphies for tribes) and Zomlefer (1994; Table 14, pp. 206-207) especially for additional distinguishing characteristics (in parentheses, subfamilies I, Barnadesioideae; II, Cichorioideae; III, Asteroideae).

TRIBE DISTRIBUTION HABIT CAPITULA PERIANTH
Anthemidae (III) 108/1725, cosmop. herbs, some shrubs heterogamous K none, or ring or cup; C tubular or tubular/ligulate
Arctotideae (II) 18/200, warm, esp. S Africa herbs, shrubs heterogamous K none, or not capillary; C usually tubular and ligulate
Astereae (III) 178/2700, cosmop. herbs, shrubs, some trees heterogamous K various, C tubular or tubular/ligulate
Barnedesieae (I) 9/92, S. America shrubs, small trees or herbs (97% woody) homo- or heterogamous K bristles with long hairs; C tubular or ligulate
Calenduleae (III) 8/85, Africa, SW Asia, Europe herbs, shrubs heterogamous K none, C tubular/ligulate
Cardueae (II) 79/2500, mostly Eurasia herbs, one pachycaul tree homogamous (or with sterile outer flowers) K capillary, C tubular
Eupatorieae (III) 169/2400, mostly New World herbs, shrubs homogamous K 5-many bristles or scales, or none; C tubular
Gnaphalieae (III) 183/2050, cosmopolitan, esp. S. Afr., Australia herbs, shrubs, or shrublets (often ericoid) homogamous (mostly) K usually capillary bristles, C tubular (rarely tubular/ligulate)
Helenieae (III) 93/635, America, esp. N.; few Old World herbs, trees in one genus heterogamous  
Heliantheae (III) 196/2500, cosmop., esp. America herbs, shrubs, trees, lianes heterogamous K usually 2-3 awns or scales, C tubular or tubular/ligulate; NB black anthers
Inuleae (III) 38/480, Old World, esp. Eurasia perennial herbs, shrubs, tree heterogamous K scales or capillary bristles, C tubular/ligulate
Lactuceae (II) 97/1530, cosmop., esp. N. hemisphere herbs, some pachycaul trees; produce latex homogamous K simple or plumose, C ligulate
Liabeae (II) 14/160, tropical New World shrubs or trees homo- or heterogamous K usually capillary bristles, C tubular or tubular/ligulate
Mutiseae (II) 77/950, warm herbs, lianes, trees homo- or heterogamous K capillary, C variable, bilabiate (2+3) or ligulate
Plucheeae (III) 28/180, trop. and warm, incl. arid herbs, shrubs, trees homo- or heterogamous K scales or capillary bristles, C tubular
Senecioneae (III) 119/3225, cosmop. herbs, shrubs, trees, lianes homo- or heterogamous K capillary, C tubular or tubular/ligulate
Vernonieae (II) 98/1530, mostly tropical herbs, shrubs, trees homogamous K setose, C tubular (rarely ligulate)

See content from The International Compositae Alliance's new book, Systematics, Evolution, and Biogeography of the Compositae (Funk, Susanna, Stuessy & Bayer 2009) HERE:

The International Compositae Alliance


The Flora North America treatment of the Asteraceae (Barkley, Brouillet & Strother 2006) is available HERE:

Flora North America - Asteraceae



Asteraceae

The Families of Flowering Plants
DELTA database in natural language

L. Watson and M. J. Dallwitz


Asteraceae

Images from Botany at the University of Hawaii

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