This page contains photos and description of a species, form or cultivar of Costaceae.

Gingersrus Database Taxon ID 6082

Chamaecostus acaulis

OLD NAME: Chamaecostus acaulis

NEW NAME: Chamaecostus acaulis


FULL SCIENTIFIC NAME: Chamaecostus acaulis (S.Moore) T.Andr? & C.D.Specht comb. nov.

STATUS : accepted

CONTINENT: Neotropical

FIELD OBSERVATIONS:(If field observations are available, you can click on the link to open in a new window.)

PHOTOS:(If photos are available, you can click on the link to open in a new window.)

- Costus acaulis Sp.Moore (1895) - Costus kaempferoides Loes. (1929) - Costus steinbachii Loes. (1929)

There is a rather large complex of similar looking plants that have been published under different names, all having an acaulescent (more or less stemless) form and producing bright yellow flowers. In his 1972 monograph, Paul Maas placed ten of these names into synonymy with Costus warmingii which was described in 1890 and included in Schumann's Das Pflanzenreich. Then in his 1977 additions to his monograph Maas reported he had found an earlier name (Globba subsessilis) that had been applied to this form from a collection in Bahia, Brazil and he replaced the name with Costus (now Chamaecostus) subsessilis. Maas had placed into synonymy 11 species names and combined them ultimately into C. subsessilis, noting it to be a complex needing further study.

In February 2015, Thiago André completed his doctoral thesis, studying this group of plants over their wide range from eastern Brazil to Bolivia and Peru in the west. He took detailed measurments of the leaf shapes and completed a molecular phylogeny that included sampling from across the range of this group of plants. He concluded that:

"Most species within the genus Chamaecostus (Costaceae) are well defined, but thereis a broad geographic range and long list of synonyms associated with Chamaecostussubsessilis, which could indicate the presence of some cryptic species within this speciescomplex. Indeed, while Chamaecostus is strongly monophyletic, C. cuspidatus is found to besister to a clade of some but not all samples of C. subsessilis, making it necessary toacknowledge more than one species in the C. subsessilis complex. Leaf morphometricmeasurements of herbarium specimens reveal limited distinction among phylogeneticlineages, demonstrating a cryptic speciation scenario."

André's research was published in Phytotaxa 204 (4): 265-276, and this species was re-established as an accepted name for the former Chamaecostus subsessilis plants found west of the Araguaia River basin, based on both morphology and his phylogenetic research. André did extensive sampling across the geographic range and completed a phylogenetic analysis of 9 specimens. He also studied the morphological traits across the range and in particular measured leaf size and angle of the base and apex of the leaves. He found there were at least two widely separated genetic lineages, one from eastern Brazil in a clade close to C. cuspidatus and the plants from western Brazil to Bolivia and southeastern Peru in a separate group. He described C. acaulis and distinguished it from C. subsessilis by having a shorter habit, and larger, broader, more puberulous leaves. He suggested that there may be some overlap between the two species, especially in the Aruguaia River basin and that geographic origin should be taken into account to assist in identification.

The type specimen for Chamaecostus acaulis is from Mato Grosso, Brazil. André has assigned two of the eleven names from this group of plants to be synonyms of this species:

  1. Costus steinbachii Loes., from Buenavista in Santa Cruz, Bolivia.
  2. Costus kaempferoides Loes., from the Rio Acre in Madre de Dios, Peru.

I have been to both of these localities and I am growing plants from seeds collected in those regions. I am also growing the commonly cultivated form that according to Tim Chapman was originally collected somewhere in Boliva. The three plants in my garden all have densely puberulous leaves (both sides) but are quite different looking vegetatively. My collection from Bolivia (R3391) is mature and in flower, has leaves 32 cm long by 10 cm wide with sheaths raising the leaves up to as much as 25 cm tall. The Peruvian collection (R3427) is much younger but also in flower and it has leaves only 19 cm long by 8 cm wide and barely 1 cm above the ground. My collection from cultivation with the name 'Fruit Loops' (R3398) has much longer, narrower leaves 35 cm long by 10 cm wide and is completely acaulescent, with sheaths 2 to 5 cm long. Previously I had another cultivated plant (R2839) but has since been lost. The three current growing collections look quite different from each other but all three are from western parts of the complex's range and should be included in C. acaulis. I also took measurements from R2839 when it was still alive. It is reported to be a collection from Bolivia and it appears to be consistent with the leaf size and angles with the plants that have now been split back out to Chamaecostus acaulis but could fit within the ranges described for C. subsessilis.
Average apex angle (AA) = 61 °
Average base angle (BA) = 42 °
Leaf lengths (cm) 30.7 27.0 28.5
Leaf widths (cm) 9.0 8.6 8.5

In my opinion, this species cannot be distinguished from the C. subsessilis in eastern Brazil by the leaf morphology and height of the sheaths. There is simply too much variation, even with multiple plants within the same population, depending on the maturity and environmental conditions. Possibly they could be distinguished by the indumenta if the C. subsessilis plants from the east are consistently glabrous on the upper sides of the leaves and if the plants to the west are consistenly densely puberulous. Photos of these collections and other observations can be found at the inaturalist and photo album links above.

C. acaulis is quite common over a wide range in western Brazil, southeastern Peru and Bolivia. As with most Chamaecostus, it is ususally found in large populations with many plants growing together in clumps rather than single plants spread apart as in Costus. It has not been assessed for IUCN Red List but would certainly be of "Least Concern" regarding endangerment in the wild. It flowers during the first months after the dry season, with peak flowering in October and November in its native areas. During the dry season, it usually goes dormant and completely disappears, surviving on the tuberous roots.

I have seen this form sold under a cultivar name of 'Fruit Loops'. It is a deciduous plant with thick tubers on the roots which allow it to survive a period of dormancy during the dry period in native habitats and in cultivation it can survive light freezes during the winters, then resprout in spring. This species is not listed at any of the reporting botanical gardens in the BGCI network, but probably some accessions are still listed under C. subsessilis.

ACCESSIONS:Click links (if any) to see details of individual collections. R3391- R3398- R3427- R3516-

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Photos (if available) of Taxon ID 6082
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Chamaecostus acaulis form, from Skinner R3391 from Santa Cruz, Bolivia - Click to see full sized image
Photo# 20 Accession# R3391
Chamaecostus acaulis form, from Skinner R3391 from Santa Cruz, Bolivia