PLANT FAMILY: Costaceae
BOTANICAL NAME: Chamaecostus acaulis
FORMAL SCIENTIFIC NAME: Chamaecostus acaulis (S.Moore) T.AndrÃ© & C.D.Specht comb. nov.
SYNONYMS: Costus acaulis Sp.Moore (1895), Costus kaempferoides Loes. (1929), Costus steinbachii Loes. (1929),
This species is re-established as a proper name for the former Chamaecostus subsessilis plants found west of the Araguaia River basin, based on both morphology and phylogenetic research of Thiago AndrÃ©. Maas had placed into synonymy 11 species names and combined them ultimately into C. subsessilis, noting it to be a complex needing further study. AndrÃ© did extensive sampling across the geographic range and completed a phylogenetic analysis of 9 plants. 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 plant commonly found in cultivation in the USA as Chamaecostus (or Costus) subsessilis 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.