Gingersrus Database Taxon ID 7633
CURRENT NAME: Costus sp. nov.
PROPOSED NAME: Costus rubineus
NAME CHANGE NOTES: New species published March 22, 2023 in PhytoKeys 222: 75-127, similar to C. scaber but with longer calyx and other differences, high elevation form
FULL SCIENTIFIC NAME: Costus rubineus D.Skinner & Maas
STATUS : sp. nov.
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Costus rubineus was published March 22, 2023 in PhytoKeys 222: 75-127 by Dave Skinner and Paul Maas. I first saw this new species in 2008 in nothern Peru in the Alto Mayo reserve. I thought it looked somewhat like Costus scaber, but there were several differences. The plants there did not have the characteristic line of hairs on the upper midrib of the leaves, the calyx was long - not short and wide as in C. scaber and the sheaths and lower side of the leaves were densely hairy. This plant form, found at elevations over 1200 meters in Alto Mayo, was entirely different looking from the C. scaber I had seen in the valley below near Rioja. The inflorescences also had a "twisted" shape, so I later registered this under the cultivar name Costus 'Twister'.
The next time I saw this species was in 2016 in Department Huanuco, Peru near the village of Chinchao at an elevation of nearly 2000 meters. The Spanish explorer Hipolito Ruiz had made a collection here that he called Costus ruber in his journal, but his specimen was lost in a shipwreck off the coast of Portugal, and he never mentioned the name again in his journal. He also collected a specimen he called Costus scaber, but the form I saw at lower elevations was consistent with the ususal C. scaber - not like this high elevation plant with its longer calyx.
Finally, in 2017 I was exploring the area around Oaxapampa in Department Pasco, Peru and I saw several examples of this same species at the higher elevations, and the "normal" Costus scaber at the lower elevations. After consultation with Paul Maas we decided this is indeed a new species. I decided to name it Costus rubineus in recognition of the Costus ruber that had been lost from Ruiz's collections in the shipwreck. (The name Costus ruber had already been used by someone else in another species.) This new species is only known from the eastern flanks of the Peruvian Andes at elevations between 1200 and 2000 meters.
The full description, drafted by Dr. Maas, points out the differences between this new species and Costus scaber. Dr. Maas selected as a holotype a collection by Rojas, Gonzales, et. al. 3574 which was was collected at the same localty as my number R3422.
A partial phylogeny was completed by Eugenio Valderrama and his associates in the Chelsea Specht Lab at Cornell University and was published in the journal Frontiers in Plant Science in September 2022. A tissue sample from a plant in Oaxapampa has been included in the molecular phylogeny and found to be well separated from several samples of the similar looking species, Costus scaber, thus verifying that it is indeed a separate species.
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