Gingersrus Database Taxon ID 7773Costus acreanusOLD NAME: Costus acreanus NEW NAME: Costus acreanus NAME CHANGE NOTES: No change in names but species was expanded to include the form known as the 'El Gato' form based on similarities with the type from Acre, Brazil. THIS IS NOW UNCERTAIN! FULL SCIENTIFIC NAME: Costus acreanus (Loesener) Maas STATUS : accepted CONTINENT: Neotropical FIELD OBSERVATIONS:(If field observations are available, you can click on the link to open in a new window.) FIELD OBSERVATIONS PHOTOS:(If photos are available, you can click on the link to open in a new window.) GOOGLE PHOTO ALBUM SYNONYMS: - Costus cylindricus Jacq. var. acreanus Loes. (1929) BOTANICAL NOTES: For years I was terribly confused by this species, and just when it seemed we had solved that confusion, the DNA told us a different story! The type for Costus acreanus was from the Rio Acre in Madre de Dios, Peru near the Brazil border. It was collected by Ernst Ule in 1911 and the herbarium specimen is at Kew Gardens in UK. Very few details are visible on the specimen. It was originally described by Loesener in 1929 as Costus cylindricus var. acreanus. There was another Ule collection from the same region that Loesener called Costus validus which was lost in Berlin, and is listed by Dr. Maas as a synonym for C. arabicus. From looking at the photograph and reading the Loesener description, I have wondered if possibly that was the species we are now calling Costus acreanus, and perhaps Loesener's Costus cylindricus var. acreanus is really the plant with the tubular flower that is proposed as a sp. nov. Costus pseudospiralis, which is also common in the region of the Rio Acre. The description in the 1972 monograph depicted a short plant (1-2 meters tall), with sheaths, ligules and leaves only minutely puberulous or glabrous, an inflorescence that could be either terminal on a leafy stem or basal on a separate leafless shoot, with a densely velutinous bract, bracteole and calyx. The flowers were not fully described, based only on the descriptions by the collectors - Ule for the type and Pires & Black from a collection at Quince Mil in Cuzco, Peru. There was nothing in the description to indicate a pendent or nodding inflorescence which has turned out to be the most obvious and distinctive character of this species when seen in the field. The illustration in the monograph clearly shows bracts with foliacous appendages, but the description did not mention appendages at all! It seems to be based upon a specimen from Colombia, Plowman 2298, which I have doubts about its determination as C. acreanus. It was not until January of 2020 that I began to fully understand this species. I traveled to the southern part of the state of Acre in Brazil, in the region along the Rio Acre and into adjacent Peru. There, I found thousands of plants of this species, and took many photographs and documented the details of the plants and their flowers to help revise the description for a forthcoming revised monograph. To my surprise, what I found was a species that almost always has a pendent or nodding inflorescence with dark puple, non-appendaged bracts, and open labellum flowers either mostly white or pink colors, and with a stature at least 2-3 meters tall. It was the same basic form I had first seen in 2007 in southern Ecuador - a plant I registered with the cultivar name 'El Gato'. If we include the 'El Gato' form, Costus acreanus' range extends at least from southern Colombia as far south as Beni in Bolivia, and is most common in southern Peru and western Brazil. It is quite distinctive in the field based on the pendent inflorescence, and in herbarium specimens a sharp bend can sometimes be seen at the base of the inflorescence. It is somewhat variable in form, sometimes having dark puple undersides to the leaves in the southern part of its range, but not in the 'El Gato' plants of Ecuador and Colombia. Plants there usually have red dots on the basal part of the sheaths, and the labellum wings are often parallel to each other giving the flower a flattened appearance. A basal inflorecence (on a leafless or nearly leafless shoot) is sometimes found to the south but I have never seen plants in Ecuador or Colombia flowering basally. The hairiness (as in most Costus) is quite variable, but generally there are velutinous bracts, bracteole and calyx as described. In the many plants I have observed in the field I have not seen hairs on the corolla lobes and only once saw the the calyx exceed the bracts (at Manu Learning Centre), except when a plant is in fruit and the bracts were open. We had planned to describe a new species to be called Costus pendens based on the plants I had seen in Ecuador and Colombia, but after I visited the type locality of Costus acreanus and saw the plants there nearly all with the same pendent inflorecence, we decided the Ecuadorian and Colombia plants must also be included in the species C. acreanus. For this species I have created a special page to show the variation in Costus acreanus across its range. You can see this page by clicking on the link to go to Google Photos. We thought we had finally solved this species until a recent molecular phylogeny was completed that included plants from the region of the type locality as well as the 'El Gato' collection (R3079) from Ecuador. It turned out that R3079 is in a separate lineage from the samples from Acre, Brazil and Madre de Dios, Peru in the south, and the 'El Gato' form may be an undescribed new species after all! It was found in a separate clade in a lineage with the new species Costus convexus. Additional research and perhaps inclusion of an 'El Gato' sample from Colombia is needed to resolve this question. For now, I am separating the "El Gato Form" to a separate page on this website to be found at the following link: http://www.gingersrus.com/DataSheet.php?PID=7509.
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