Chironieae

Rosepink Sabatia angularis, copyright Allen Gathman.

Belongs within: Gentianales.
Contains: Coutoubeinae, Canscorinae, Centaurium, Chironia.

The new centaury
Published 1 January 2021

In an earlier post, I described the South American flowering herbs known as the Coutoubeinae. In this post, I’m going to take a step back and look at a clade of which the coutoubeines form a part, the Chironieae.

Seaside centaury Centaurium littorale, copyright Anne Burgess.

The Chironieae are one of the major tribes of the flowering plant family Gentianaceae, including about 160 known species. Representatives are found in most parts of the world, though as part of the native flora in Australasia they do not extend past the north of Australia (some exotic species have been introduced further south). The Chironieae seem to primarily be supported as a clade on the basis of molecular data (Struwe et al. 2002). All members are herbs, from annuals to short-lived perennials. Most have an erect growing habit; members of the Caribbean genus Bisgoeppertia are annual climbers and some species of the Mexican genus Geniostemon are creeping perennials. There may or may not be a basal rosette of leaves, and a number of genera have winged stems. Flowers are solitary or borne in cymose or racemose inflorescences. These flowers are most commonly salver-shaped (that is, shaped like a flat dish) or tubular, and usually have four or five petals (some species may have up to twelve). The calyx is usually comprised of fused sepals and is unwinged and tubular. The fruit is usually a septicidal capsule (splitting along the septa between carpels), more rarely a berry.

Yellow centaury Cicendia filiformis, copyright Hajotthu.

Members of the Chironieae are divided between three subtribes that are mostly distinct both morphologically and biogeographically. As described in the previous post, the Neotropical Coutoubeinae are characterised by releasing their pollen in tetrads whereas the other subtribes shed individual pollen grains. The Canscorinae are mostly found in the Old World tropics and have white or cream-coloured flowers (less commonly yellow, pink or purple) with the calyx tube longer than the calyx lobes. The Chironiinae mostly includes found in northern temperate regions, as well as the southern African genera Chironia and probably the South American Zygostigma. Their flowers come in a range of colours—pink, yellow, purple or blue, but less commonly white or cream-coloured—and may have calyx lobes longer than the tube. Many chironiine flowers also have anthers that become spirally twisted after releasing pollen whereas those of Canscorinae are always straight. Molecular data usually support the monophyly of the three subtribes and the majority view seems to be that the temperate Chironiinae represent the sister group of a tropical clade of Canscorinae and Coutoubeinae.

Cultivated Eustoma, copyright Rameshng.

Perhaps the best known members of the Chironieae are the centauries of the genus Centaurium. Historically, about fifty species across the Holarctic have been included in this genus. However, phylogenetic studies have demonstrated that this broad sense of the genus is polyphyletic and thus it has been cut down to a group of about twenty species found in Europe and western Asia. The name ‘centaury’ refers to the use of common centaury Centaurium erythraea as a medicinal herb, after the legendary centaur healer Chiron. Other Old World species are now placed in the genus Schenkia whereas North American species form the genera Gyrandra and Zeltnera. The yellow centauries of Cicendia are small, filiform annuals native to Europe and the Americas that have been introduced to Australia. The rose gentians Sabatia of North America bear pinkish-purple flowers, often in lax cymes. There are also the prairie gentians of the genus Eustoma. Native to southern North America, these plants bear large, showy flowers that have become popular in cultivation. Commercially, they are labelled as lisianthus. This is not to confused with Lisianthius, a distinct genus of Gentianaceae, or Lisyanthus, a name that has been used in the past for members of yet another gentianaceous genus. Both of these belong to completely different tribes in the family, and may be subjects for another day.

Systematics of Chironieae
<==ChironieaeSK02
|--+--CoutoubeinaeSK02
| `--CanscorinaeSK02
`--Chironiinae (see below for synonymy)SK02
| i. s.: Bisgoeppertia Kuntze 1891SK02
| |--*B. volubilisSK02
| `--B. scandensBC02
| Zygostigma Grisebach 1839SK02
| |--*Z. australeSK02 [=Sabbatia australisG39]
| `--Z. uniflorum [=Erythraea uniflora]G39
| Orthostemon erectus [=Exacum erectum]G39
| SchuebleriaG39
| |--S. confertaG39
| |--S. diffusa [incl. Exacum brachiatum]G39
| |--S. patulaG39
| |--S. pusilla Grisebach 1839G39
| |--S. stricta [incl. Sabbatia verticillaris]G39
| `--S. tenellaG39
| Apophragma tenuifolium [=Exacum tenuifolium; incl. E. violaceum]G39
| ChloraG39
| | i. s.: C. grandifloraD17 [=C. perfoliata var. grandifloraG39]
| | |--C. g. var. grandifloraD17
| | `--C. g. var. trimestrisD17
| | C. quadrifolia [=Gentiana quadrifolia]G39
| `--C. sect. Urananthus Grisebach 1839G39
| `--C. (sect. *U.) exaltata (see below for synonymy)G39
|--+--Ixanthus Grisebach 1839SK02
| | `--*I. viscosusSK02 [=Gentiana viscosaG39]
| `--Blackstonia Hudson 1762SK02 [incl. Chlora sect. Xanthanthus Grisebach 1839G39]
| |--*B. perfoliataSK02 [=Chlora perfoliataBR65, Gentiana perfoliataG39]
| | |--B. p. var. perfoliataG39
| | |--‘Chlora’ p. var. acuminataG39
| | `--‘Chlora’ p. var. sessilifolia [incl. C. serotina]G39
| |--B. grandifoliaBC02
| |--B. imperfoliataSK02 [=Chlora imperfoliataG39; incl. C. crenulataG39, C. dubiaG39]
| | |--B. i. var. imperfoliataG39
| | `--‘Chlora’ i. var. lanceolataG39
| `--B. intermediaBC02 [=Chlora intermediaG39]
`--+--+--Geniostemon Engelmann & Gray 1881SK02
| | |--*G. coulteriSK02
| | |--G. gypsophilumSK02
| | `--G. schaffneriBC02
| `--+--Exaculum Caruel 1886SK02
| | `--*E. pusillumSK02 (see below for synonymy)
| `--Cicendia Adanson 1763SK02, BR65
| | i. s.: C. pulchella (n. d.)G39
| |--C. sect. MicrocalaG39
| | |--*C. filiformisSK02 [=Gentiana filiformisBR65, Microcala filiformisBR65]
| | `--C. quadrangularisBR65 (see below for synonymy)
| `--C. sect. HippocentaureaG39
| |--C. candollei [=Exacum candollei; incl. E. glaucum]G39
| |--C. exaltataG39
| `--C. fastigiata [=Exacum fastigiatum]G39
`--+--+--CentauriumSK02
| `--+--ChironiaSK02
| `--Orphium Meyer 1838SK02
| `--*O. frutescensSK02
`--+--Eustoma Salisbury 1806SK02
| |--*E. silenifoliumSK02
| |--E. exaltatumH93
| |--E. grandiflorumSK02
| `--E. russellianumSK02
`--Sabatia Adanson 1763SK02
| i. s.: S. brevifoliaBC02
| S. elliotiiJS02
|--S. sect. Eusabbatia Grisebach 1839G39
| |--*S. dodecandraSK02 [=Chironia dodecandraG39, Chlora dodecandraG39]
| |--S. angularis [=Chironia angularis]G39
| |--S. brachiataG39
| |--S. calycosa [=Chironia calycosa; incl. Gentiana calycina, C. dichotoma]G39
| |--S. campestrisG39
| |--S. chloroides [=Chironia chloroides]G39
| | |--S. c. var. chloroidesG39
| | `--S. c. var. stricta [incl. Chironia decandra]G39
| |--S. corymbosa [incl. Swertia difformis, Chironia cymosa, C. lanceolata, C. paniculata]G39
| |--S. gracilis [=Chironia gracilis; incl. C. campanulata, Sabbatia campanulata]G39
| |--S. macrophyllaG39
| |--S. paniculataG39
| `--S. stellarisG39
`--S. sect. Pseudochironia Grisebach 1839G39
`--S. (sect. *P.) gentianoidesG39

Chironiinae [Chironiae, Chloreae, Chlorinae, Erythraeaceae, Erythraeariae, Erythraeeae, Erythreae, Sabatieae, Sabbatieae, Teleiandrae]SK02

Chlora exaltata [=Gentiana exaltata, Lisianthus exaltatus; incl. L. glaucifolius, Erythraea plumieri]G39

Cicendia quadrangularisBR65 [=Gentiana quadrangularisG39, Exacum quadrangulareG39, Microcala quadrangularisBR65; incl. E. chilenseG39, E. inflatumG39]

*Exaculum pusillumSK02 [=Cicendia pusillaSK02, Exacum pusillumG39, Gentiana pusillaG39; incl. Erythraea luteolaG39, Chironia minimaG39]

*Type species of generic name indicated

References

[BR65] Black, J. M., & E. L. Robertson. 1965. Flora of South Australia. Part IV. Oleaceae–Compositae. W. L. Hawes, Government Printer: Adelaide.

[BC02] Bouman, F., L. Cobb, N. Devente, V. Goethals, P. J. M. Maas & E. Smets. 2002. The seeds of Gentianaceae. In: Struwe, L., & V. A. Albert (eds) Gentianaceae: Systematics and Natural History pp. 498–572. Cambridge University Press: Cambridge.

[D17] Diels, L. 1917. Beiträge zur Flora der Zentral-Sahara und ihrer Pflanzengeographie. Nach der Sammelausbeute des Freiherrn Hans Geyr von Schweppenburg. Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie 54 (Beiblatt 120): 51–155.

[G39] Grisebach, A. H. R. 1839. Genera et Species Gentianearum adjectis observationibus quibusdam phytogeographicis. J. G. Cotta: Stuttgardt.

[H93] Hickman, J. C. (ed.) 1993. The Jepson Manual: Higher Plants of California. University of California Press: Berkeley (California).

[JS02] Jensen, S. R., & J. Schripsema. 2002. Chemotaxonomy and pharmacology of Gentianaceae. In: Struwe, L., & V. A. Albert (eds) Gentianaceae: Systematics and Natural History pp. 573–631. Cambridge University Press: Cambridge.

[SK02] Struwe, L., J. W. Kadereit, J. Klackenberg, S. Nilsson, M. Thiv, K. B. von Hagen & V. A. Albert. 2002. Systematics, character evolution, and biogeography of Gentianaceae, including a new tribal and subtribal classification. In: Struwe, L., & V. A. Albert (eds) Gentianaceae: Systematics and Natural History pp. 21–309. Cambridge University Press: Cambridge.

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