Maas, P.J.M. & Maas-van de Kamer, H. (2009). Neotropical Costaceae.
Perennial often large-sized herbs, with rhizomes. Stems terete , straight or spirally contorted , containing an acid juice. Leaves spirally arranged, with closed sheaths and a truncate or 2- lobed ligule . Inflorescence a spike , terminal on a leafy stem or sometimes on a separate leafless, basal shoot , rarely flowers solitary in the axils of the upper leaves (Monocostus K.Schum.); bracts often brightly coloured, coriaceous to herbaceous , imbricate , each subtending 1 flower , with a linear callus just below the apex ; bracteole 1, folded or tubular. Flowers zygomorphic ; calyx tubular, 3- lobed ; petals 3, connate into a distinct tube; fertile stamen 1, petaloid , anther 1, usually attached at the middle; labellum equaling or much exceeding the corolla , tubular or horizontally spreading; style 1, filiform , lying close to the stamen and embraced by the thecae, stigma 1, 2-lamellate with a 2- lobed appendage or cup-shaped and unappendaged, margins ciliate ; ovary inferior, 2-3-locular, with 2 septal nectarial glands towards the apex , placentation axile , ovules many, anatropous. Fruit a white capsule , 3- or 2-locular, crowned by the persistent calyx , often irregularly and tardily dehiscent . Seeds many, angular- ovoid to 4-sided, with a white aril , glossy black or brown.
Distribution in the Neotropics
Family: From Mexico in the North to S Brazil and N Paraguay in the South, also present in the West Indian Islands.
- Chamaecostus C.D.Specht & D.W.Stev. - Colombia, Venezuela, the Guianas, and Amazonian and SE Brazil, and Bolivia.
- Costus L. - throughout he Neotropics.
- Dimerocostus Kuntze (3 spp.) - from Honduras in he North to Peru and Bolivia in the South.
- Monocostus (1 sp.) - Eastern Peru.
Key differences from similar families
Costaceae have various flower characters in common with Zingiberaceae, but they differ by having:
- Non-aromatic leaves.
- Closed leaf sheaths.
Key to genera of the Neotropical Costaceae
1. Flowers solitary in the axils of the upper leaves...Monocostus
1. Flowers in a terminal spike... 2
2. Ovary 2-locular; bracteole tubular...Dimerocostus
2. Ovary 3-locular; bracteole folded or tubular... 3
3. Low or very small, occasionally acaulescent plants, never exceeding 1 m in height; bracts herbaceous to chartaceous, green or yellow; bracteole tubular, bicarinate at the abaxial side; stigma cup-shaped...ChamaecostusNotable genera and distinguishing features
3. Tall, gigantic, or low plants, usually over 1 m tall; bracts coriaceous, rarely chartacous, red, orange, yellow or green; bracteole folded; stigma 2-lamellate, always provided with a dorsal 2-lobed appendage...Costus
- Monocostus is unique in the family in having solitary, axillary flowers; it is endemic to Eastern Peru, where it grows in forests on limestone.
- Chamaecostus has been recently separated from Costus by Specht et al. (2001, 2006) based on molecular evidence. Formerly it had been placed (see Maas, 1972) in Costus subgenus Cadalvena Fenzl.
- Stems with an acid juice.
- Leaves spirally arranged, with a ligule and a closed sheath.
- Inflorescence a spike, covered with often brightly coloured bracts (except for Monocostus).
- Flowers zygomorphic.
- Stamen 1, petaloid.
- The largest part of the flower is the tubular to spreading lip (labellum).
- Calyx tubular and persistent on top of the fruit.
- Inflorescenceterminal on the leafy stem or on a separate, leafless, basalshoot.
- Most species have thick, coriaceous bracts; in some species the bracts are chartacous to herbaceous.
- General Description
Number of genera
- Chamaecostus (7 spp.)
- Costus (ca. 50 spp.)
- Dimerocostus (2 spp.)
- Monocostus (1 sp.)
- All genera are native.
The petaloid labellum of Costaceae has been supposed to consist of 5 staminodes.Notes on delimitation
- Costaceae were formerly treated as a subfamily of Zingiberaceae (Costoideae), but recent research revealed that they should be treated as a family of its own. The family belongs in the Zingiberales.
Larsen, K. 1998. Costaceae. In: K. Kubitzki (ed.), The families and genera of vascular plants 4: 128-132.
Maas, P.J.M. 1972. Costoideae (Zingiberaceae). Flora Neotropica Monograph 8: 1-140.
Maas, P.J.M. 1972. Renealmia (Zingiberaceae- Zingiberoideae). Costoideae (Additions) (Zingiberaceae). Flora Neotropica Monograph 18: 162-219.
Specht, C.D. 2006. Systematics and evolution of the tropical monocot family Costaceae (Zingiberales): A multiple dataset approach. Syst. Bot. 31: 89-106.
Specht, C.D., & Stevenson, D.W. 2006. A new phylogeny-based generic taxonomy for the monocot family Costaceae (Zingiberales). Taxon 555: 153-163.
Specht, C.D., Kress, W.J., Stevenson, D.W., & DeSalle, R. 2001. A molecular phylogeny of Costaceae (Zingiberales). Mol. Phyl. Evol. 21: 333-345.
First published in J. Jap. Bot. 17: 203. 1941 [Apr 1941] (1941)
- APG IV (2016) http://dx.doi.org/10.1111/boj.12385
Kew Names and Taxonomic Backbone
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Milliken, W., Klitgard, B. and Baracat, A. (2009 onwards), Neotropikey - Interactive key and information resources for flowering plants of the Neotropics.