Costus osae 

Scope: Global
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Taxonomy [top]

Kingdom Phylum Class Order Family
Plantae Tracheophyta Liliopsida Zingiberales Costaceae

Scientific Name: Costus osae Maas & H.Maas
Taxonomic Source(s): The Plant List. 2013. The Plant List Version 1.1. Available at: (Accessed: 29/9/2013).
Taxonomic Notes: Costus osae was described by Paul and Hiltje Maas in 1997. It is easily identified by the broad felty leaves and bright red appendaged bracts with red flowers. Identification can be confirmed by dissecting the inflorescence and checking the bracteoles which are two-keeled (bicarinate) instead of the usual single keeled canoe shape of the bracteoles of other Costus species. Within the genus, the only other species with this character is Costus ricus Maas and H. Maas.

This species is a wild relative of cultivated ornamental ‘spiral gingers’, such as Hellenia speciosa (J.Koenig) Govaerts, comb. nov.  (Crepe Ginger) (formerly Costus speciosus Koen ex. Retz.), C. scaber Ruiz & Pav. (Indian Head Ginger), C. comosus (Jacq.) Roscoe (Red Tower Ginger), C. woodsonii Maas (French Kiss), and C. productus Gleason ex Maas (Orange Tulip Ginger).

Assessment Information [top]

Red List Category & Criteria: Vulnerable D1 ver 3.1
Year Published: 2015
Date Assessed: 2015-07-22
Assessor(s): Skinner, D.
Reviewer(s): Magos Brehm, J.
Contributor(s): Magos Brehm, J.
Costus osae is endemic to a small area in the Golfo Dulce region of Costa Rica. It is found in a very specific habitat of rocky areas along creeks and parts of its current area of occupancy are unprotected and subject to disturbance. Some subpopulations are inferred to be declining but there appear to be sufficient stable subpopulations in protected areas so this species is assessed as Vulnerable based solely on the population estimate of less than 1,000 mature individuals.

Geographic Range [top]

Range Description:Costus osae is endemic to the area near the Osa Peninsula in southeastern Costa Rica. It is found mostly in two areas, in the northern part of the peninsula between Rancho Quemado and Rincon, and in the forests to the north of  the town of Golfito across the Golfo Dulce. It is found in rocky terrain along the banks of creeks and rivers at altitudes ranging normally from 50 to 400 m asl. One anomalous collection record at 900 m asl, to the east of the predominant range of this species is accepted and included in the data.

The extent of occurrence (EOO) calculates to 544 km2 using GeoCAT to draw a polygon around the sites of the collection records. The area of occupancy (AOO) calculates to 215 km2 using the auto-value in GeoCAT to create cells about 4.9 km wide around the collection sites. GeoCat 4.9 km automatic grid size was used to create an inferred AOO based on knowledge of the habitats and protected areas within the EOO where there is a very high likelihood of presence at other sites beyond the recorded sites.

Countries occurrence:
Costa Rica (Costa Rica (mainland))
Additional data:
Estimated area of occupancy (AOO) - km2:215Continuing decline in area of occupancy (AOO):Yes
Estimated extent of occurrence (EOO) - km2:544
Continuing decline in extent of occurrence (EOO):Unknown
Lower elevation limit (metres):50
Upper elevation limit (metres):900
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:This assessor has observed subpopulations at two localities, Quebrada Aquabuena near Rincon and the Rio Bonito/Quebrada Negra areas of the Parque Nacional Piedras Blancas. At the first site, visited in 2013, there was a sizeable subpopulation, estimated to be at least 50 mature individuals which had blanketed a small area. In the other area, visited in 2005 and again in 2011, the plants were more isolated with only three to five plants seen together at a given site. In several trips to the Osa Peninsula, this assessor has not seen this species in the southern part of the Peninsula or in the western part near Drake or the San Pedrillo area of the Corcovado National Park, nor have collections been recorded in those parts of the Golfo Dulce region. Based on these observations and communication from Reinaldo Aquilar who lives in the area, this assessor estimates a total population size of 300-500 mature individuals that is decreasing to some extent, but not quantifiable.
Current Population Trend:Decreasing
Additional data:
Number of mature individuals:300-500Continuing decline of mature individuals:Yes
Extreme fluctuations:UnknownPopulation severely fragmented:Unknown

Habitat and Ecology [top]

Habitat and Ecology:This species is found in a very specific habitat, below steep rocky slopes and along banks of creeks and small rivers growing in rocky soil. It tends to be sensitive to habitat change.

Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):8

Use and Trade [top]

Use and Trade: This species is used as an ornamental plant in gardens. It is also a wild relative of, and potential gene donor to, other species of ornamental Costus that are cultivated and sold in the horticultural trade.

Threats [top]

Major Threat(s): There is some threat of habitat loss, especially in the unprotected part of its area of occupancy (AOO) between Rancho Quemado and Rincon, on the Osa Peninsula of Costa Rica. This species is more likely than others to be affected by disturbance and wild populations could be especially hard hit by the effects of global warming as it seems to be especially sensitive to habitat change (R. Aquilar pers. comm. 2015). The area around Rancho Quemado is likely to be experiencing a reduction in numbers due to habitat loss but other areas are currently protected.

Conservation Actions [top]

Conservation Actions: Some subpopulations occur within existing protected areas but are not actively managed. The subpopulations located in the protected areas of Corcovado National Park and Piedras Blancas National Park should be actively monitored. This species is found in the living collections of several large botanical gardens and is propagated and cultivated as a popular ornamental plant, but nearly all of these are clones from a single collection and there is no current conservation of the genetic diversity of the speciesSeeds from different subpopulations should be deposited in genebanks to preserve the genetic diversity.

Citation: Skinner, D. 2015. Costus osae. The IUCN Red List of Threatened Species 2015: e.T56347828A56353118. . Downloaded on 21 July 2018.
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