Gingersrus Database Taxon ID 7643
CURRENT NAME: Costus pulverulentus - Mesoamerican form
PROPOSED NAME: Costus pulverulentus
NAME CHANGE NOTES: form in Mesoamerica with C. scaber type flower, stamen not exposing thecae
FULL SCIENTIFIC NAME:
STATUS : distinct form
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I have made three trips to southern Mexico, one trip to Guatemala and one to Honduras. In these Mesoamerican countries I have found it very difficult to distinguish between Costus pulverulentus and Costus scaber. None of the plants I have seen have had the flower form found farther south in Costa Rica and Panama. It seems that many of the plants in this region are intermediate between those two species. The shape of the inflorescence in Costus pulverulentus is described as being fusiform (pointed) but many of the plants I have seen tend to mature that way but start out with a rounded apex and most of them have a short calyx. The only way I can distinguish them is to cut under the bracts and check the length of the calyx which is normally very short in C. scaber. Most of the plants do seem to have the 60 degree angle typical of the South American form of C. scaber but the flowers of all these plants - whether C. scaber or C. pulverulentus are pretty much identical. It also seems that the indumentum on sheaths and leaves is variable. I think much more research will be needed to fully resolve the status of these plants.
There are two examples of what I believe fits best into C. pulverulentus in the Mesoamerican form. One from Oaxaca, Mexico (R3454) produces a fusiform shaped inflorescence, with fibrous margins to the bracts - thus perfectly fitting the description of that species. The flower, however, is not at all like the Central American plants, with tightly closed corolla and a stame that barely exceeds the labellum.
The other Mesoamerican example of C. pulverulentus (R3506) from Honduras is shorter than the others, has smaller round leaves and is densely hairy. It has a fusiform inflorescence with fibrous margins to the bracts, but the flower looks very much like a C. scaber flower.
Also, please see the data sheet for Costus 'Mongrel' from Bocas del Toro, Panama that looks similar to this plant form from Mexico.
I really do not know what to make of all this but it seems likely to me that in Mesoamerica we are dealing with an introgression or hybridization between C. pulverulentus and C. scaber, or possibly a separate species. Much additional research is needed.
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