Gingersrus Database Taxon ID 7787
CURRENT NAME: Costus sp. nov.
PROPOSED NAME: Costus gibbosus
NAME CHANGE NOTES: This form from Ecuador, formerly part of C. guanaiensis var. tarmicus is now published March 22, 2023 in PhytoKeys 222: 75-127 as a new species Costus gibbosus.
FULL SCIENTIFIC NAME: Costus gibbosus D.Skinner & Maas
STATUS : sp. nov.
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Costus gibbosuswas published March 22, 2023 in PhytoKeys 222: 75-127 by Dave Skinner and Paul Maas. This new species has previously been included in the former Costus guanaiensis var. tarmicus. During the research by Maas and Skinner of the Costus guanaiensis complex I visited the type locality for Costus guanaiensis var. tarmicus (f/k/a Costus tarmicus) and discovered that the plants in the region of the type locality in JunÃn, Peru are entirely different from the plants found in western Ecuador that are characterized by the distinctive swollen areas on the lower parts of the sheaths. The Ecuadorian plants also have very different bract appendages and flower colors from the plants in the Peruvian type locality for Costus tarmicus. After completing an analysis of plants in the C. guanaiensis complex, it was clear to me that these Ecuadorian plants belong to a separate species from all the others. I drafted a description of this new species and named it Costus gibbosus from the Latin gibbosus meaning "more swollen in one place than another, with a pouch-like swelling, with hump like swellings".
Paul Maas reviewed this and agreed that it should be as a new species despite the difficulty in recognizing it from dried herbarium specimens which do not ever include the lower sheaths. He selected for the type specimen a 1974 collection by Tim Plowman and Wade Davis (Plowman 4455) from western Ecuador along the road to Santo Domingo. Maas has been growing this new species at Burgers Bush and Utrecht Botanical Garden in the Netherlands, from seeds collected by Plowman. The photo at the left is a recent one of Hiltje Maas at Utrecht where this collection was in flower in December 2020. This collection is also growing at Waimea Arboretum in Hawaii, accession number 74S2037, grown from seeds collected by Plowman.
I have seen this new species many times in my trips to western Ecuador in 2007, 2009, and 2015. It usually is found with yellow flowers, but a population in the southern part of its range (near Caluma, Ecuador) was found with white flowers. The bracts appendages usually fold outward horizontally and curl under at the apex in living plants, contrasted from the Costus tarmicus forms in Peru which usually have very small triangular bract appendages that are upright and only slightly flared outward.
As of this writing (July 2022), the only DNA sample taken for this new species was my R3346, which had been extracted but not sequenced and included in the phylogeny tree.
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