﻿Eighteen new species of Neotropical Costaceae (Zingiberales)

﻿Abstract In preparation for a full taxonomic revision of the Neotropical genera of Costaceae (i.e., Chamaecostus, Costus, Dimerocostus, and Monocostus), we present the description of 17 new species of Neotropical Costus and one new species of the Neotropic endemic genus Chamaecostus with notes on their distribution and ecology, vernacular names (when known), and diagnostic characters for identification. Distribution maps are included for all species, and each description is accompanied by photographic plates illustrating diagnostic characters.


Introduction
The Neotropical members of the family Costaceae (Zingiberales) comprise two separate evolutionary lineages of species included in genera Costus, Chamaecostus, Dimerocostus and Monocostus. Originally considered a subfamily of the Zingiberaceae, they were first treated comprehensively in Floral Neogropica monographs No. 8 Costoideae (Zingiberaceae) and Monograph No. 18 Costoideae (Additions) (Maas 1972(Maas , 1977 and as part of the Flora of Suriname (Maas 1979). Species pertaining to the genus Chamaecostus, included in these monographs as Costus subgenus Cadalvena, were subsquently removed from Costus based on phylogenetic analyses demonstrating that they are in fact more closely related to Monocostus and Dimerocostus than to other species of Costus (Specht et al. 2001;Specht 2006a;Specht and Stevenson 2006). Of these genera, Chamaecostus, Monocostus and Dimerocostus are endemic to the Neotropics while Costus contains species with African distributions that appear to be ancestral to a clade of Neotropical species (Specht and Stevenson 2006;Specht 2006a, b;Salzman et al. 2015).
Recent years have also seen a rise in ecological and evolutionary studies on Costaceae, which have greatly impacted our interpretation of phenotypic patterns and evolutionary processes leading to a better understanding of species delimitations and phylogenetic relationships among taxa (Sakai et al. 1999;Specht et al. 2001;Kay and Schemske 2003;Kay et al. 2005;Kay 2006;Specht 2006a, b;Specht and Stevenson 2006;Araújo and Oliveira 2007;Kay and Schemske 2008;Yost and Kay 2009;Bartlett and Specht 2010;Specht et al. 2012;Surget-Groba and Kay 2013;Almeida et al. 2015;André et al. 2015;Morioka et al. 2015;Salzman et al. 2015;André et al. 2016;Bergamo et al. 2016;Valderrama et al. 2020;Vargas et al. 2020;André et al. 2022). These studies have helped to tease apart species complexes, identify cryptic variation, define biogeographic patterns and pollinator relationships, understand aspects of floral developmental evolution, and explore the tempo and mode of speciation and diversification across the neotropical lineages.
In the present publication, 17 new species of Costus and one new species of Chamaecostus are described. We include novel character observations made in recent years, including differences in the orientation of the flower relative to the inflorescence, a character that is variable between but consistent within species of Costus and thus useful for identification. Floral orientation may be a key feature in defining pollinator preferences and efficiencies (Fenster et al. 2009), and future studies will investigate possible functional significance. In a later study, we will incorporate these new species into a complete revision for all Neotropical Costaceae, including keys to all species, updated distribution maps, photographs with diagnostic characters, a complete index of exsiccatae (comprising ca. 11.000 entries) and a phylogenetic hypothesis to demonstrate evolutionary relationships.

Materials and methods
Material from ca. 150 herbaria was consulted for this study. A complete list of specimens examined will be provided in the forthcoming revision (Part II).
In addition, extensive field observations and collections have contributed to this study, supporting our understanding of species distributions and providing opportunities to photograph and observe key traits for distinguishing among taxa, including the colour of floral organs, orientation of the flower relative to the inflorescence (abaxial, erect, adaxial), colour of bracts, and colouration patterns of vegetative material. Field work was led by Paul and Hiltje Maas, with all co-authors participating. Dave Skinner visited most Neotropical countries and made essential observations on this group, particularly visiting type localities and taking detailed photographs, contributing to our understanding of the distribution of characters among taxa. Skinner's observations have been recorded in iNaturalist and are available at www.inaturalist.org/observations/selvadero. Living material is available in cultivation at the Fairchild Tropical Gardens in Miami, Florida, USA. Notes. For additional field data, see Costa et al. (2011), where this species has been treated under the name Costus congestiflorus.    (Figs 5,6) is well recognisable by adaxially oriented flowers, an often present ring of brown, erect and rather stiff hairs at the base of the ligule, and the abaxial leaf lamina and the bracts being often densely villose. It could be confused with Costus laevis Ruiz & Pav., but that species has much darker flowers and is often completely glabrous. Type. Colombia, Antioquia: Mun. San Rafael, along road from Guatapé to San Rafael, Río El Bizcocho, Finca El Castillo, 1059m, 12 Oct 2013isotypes JAUM, K, MO-3159234, MO-3159235).
Notes. Costus antioquiensis sp. nov. could be confused with C. allenii Maas, but in that species, the entire surface of sheaths, ligule and petiole are villose, while C. antioquiensis is highly variable in its indument. Most material has a quite dense villose indument all over the plant, but some specimens of the same population can be almost completely glabrous, especially the adaxial side of the leaves. The ring of erect hairs at the base of the ligule is almost always present in C. antioquiensis but consistently lacking in C. allenii.
Etymology. This species is named after the Bolivian department of Cochabamba, where it was collected.
Habitat and ecology. In forests, in open shade or sunny areas, often found along roadsides and other disturbed areas, at elevations of 360-1500 m. Flowering year-round.
Etymology. Costus convexus sp. nov. is named for the form of the bracts, which are distinctly convex; thus, the epithet convexus, an adjective meaning "convex or curved outwards" in Latin.
Paratypes Notes. Plants of Costus convexus sp. nov. can grow to be huge plants, up to 5 m tall, with large inflorescences and flowers. The younger shoots and leaves usually have a glaucous covering making them appear similar to C. glaucus Maas but having an inflorescence with distinctly convex bracts that are reddish or pink instead of the pale green and glaucous bracts in C. glaucus. It is also characterized by having upper leaves that wrap tightly around and, in doing so, completely hide the young inflorescence.
Etymology. This species is named for our dear colleague and friend Douglas Daly, whom PM and HM met many times in his home institute at the New York Botanical Garden Herbarium (NY) and who enabled us to undertake field work in the Brazilian regions of Acre and Amazonas. He also inspired CDS during her graduate studies at the New York Botanical Garden, providing insights into excellence in field research and tropical botany.
Habitat and ecology. In forests, in wet, shady areas, often in disturbed places, at elevations of 450-1300 m. Flowering in the rainy season.
Etymology. Costus obscurus sp. nov. is known for its leaves having a very dark green adaxial surface and dark purple abaxial surface, and for growing in dark and shady places, hence the specific epithet obscurus ('obscurus' means 'dark, shady, "indistinct' in Latin). This species might also be considered "obscure" (in English: unclear, uncertain, unknown, or in doubt) because it has been confused by the authors in the past as either C. erythrophyllus Loes. or as C. acreanus (Loes.) Maas. Only recently has it been determined to be an undescribed species.
Paratypes Notes. Plants of Costus obscurus sp. nov. have a compact appearance, with leaves closely spaced together along the shoot and generally pointed upward rather than horizontally or drooping. The leaves' dark green adaxial surface and dark purple abaxial surface are striking in appearance. Costus obscurus can be confused with C. erythrophyllus Loes., but can be distinguished from that species by its shorter, truncate ligule instead of a long and deeply 2-lobed ligule as well as by having smooth rather than (mostly) plicate leaves.
This new species has been widely cultivated from the type collection Plowman 5054. Plowman's journal indicates the distribution of live plants to Marie Selby Botanical Garden and Lyon Arboretum, which is accessioned as L-81.0901. It has sometimes been confused with the famous "El Whiskey" plant from Colombia, but it can be easily distinguished by the indumenta on the adaxial and abaxial leaf surfaces.

Costus oreophilus Maas & D.Skinner, sp. nov.
urn:lsid:ipni.org:names:77316094-1 Diagnosis. Costus oreophilus sp. nov. (Fig. 15) can be confused with C. laevis Ruiz & Pav., with which it shares the mostly green bracts and adaxially oriented flowers, but it is distinguished by the puberulous sheaths and leaves and a smaller ligule (3-10 mm vs. 5-20 mm long); moreover the corolla lobes are often recurved, a feature rarely seen in Costus.
Etymology. The species name "oreophilus" is derived from the Greek words oros (= mountain) and philos (= beloved) as this is a mountain-loving species.
Paratypes  later, we recognize these specimens merit specific rank. Costus oreophilus differs from C. convexus sp. nov. Maas & Skinner by various features such as the hairy instead of glabrous sheaths and leaves, a smaller calyx (6-12 vs. 15-25 mm long), a smaller ligule (3-10 vs. 20-45 mm long), and recurved corolla lobes, a feature quite rare in Costus.
The authors are indebted to orchid specialist Marco Jiménez Villata of Zamora, Ecuador, who has explored the forests of Zamora-Chinchipe for over 30 years. He showed Dave Skinner several localities in the province, where he was able to make photographs of this species. Skinner later found the living plants of this new species in Tungurahua, which were consistent with the plants in Zamora-Chinchipe but usually with less dense hairs on the undersides of the leaves. Moreover, in living material, the corolla lobes were found to be sharply recurved, which is very unusual in the genus Costus.
Habitat and ecology. Along forested roadsides, at an elevation of ca. 1600 m. Flowering and fruiting: May and July. Etymology. This species is named "pitalito" after its type locality near Pitalito, in the Colombian department of Cauca.
Notes. Costus pitalito looks superficially like C. leucanthus Maas by its white flowers and a very long ligule, but it differs by obtuse ligule lobes and bracts with densely brownish villose margins. Diagnosis. Costus prancei sp. nov. (Fig. 17) looks quite similar to C. sprucei Maas (a species restricted to the Brazilian state of Pará) and has been confused with it in the past, both sharing most of the vegetative and floral characters, but this species has yellow to orange flowers whereas they are pinkish red in C. sprucei.
Etymology. This species is named after our friend and dearest colleague Sir Ghillean Prance, who invited us (PM and HM) in 1971 to join various of his expeditions into the Brazilian Amazon region and who inspired me (PM) very much to continue working as a Neotropical taxonomist. Notes. We have named this species after Sir Ghillean Prance, who enabled the first author (PM) to undertake his first steps in the Amazonian world and assisted and taught him in a very kind and generous way.
Costus sprucei Maas and C. prancei sp. nov. closely resemble a third species, C. chartaceus Maas, which occurs in Amazonian Colombia, Ecuador, and Peru. They share many of the vegetative and floral features, but C. chartaceus Maas mostly has an unequally lobed ligule of 5-15 mm long, while that of the other two is truncate and 2-7 mm long. The essential difference can be found in the flower colour, which is pinkish-white in C. chartaceus (vs. pinkish-red in C. sprucei and yellow to orange in C. prancei).
The two Peruvian collections (Gentry et al. 52203 and Uliana et al. 1342) look quite similar to this species and agree in most of the floral measurements, but the leaves are quite large for this species (i.e., 25-35 × 9-13 cm). Maas & H.Maas, sp. nov. urn:lsid:ipni.org:names:77316099-1 Diagnosis. Costus pseudospiralis sp. nov. (Fig. 18) looks superficially quite similar to C. spiralis (Jacq.) Roscoe, but differs by the orientation of the flowers (floral opening facing abaxially v adaxially) and a cordate leaf base. It differs from C. douglasdalyi by the inflorescence terminating a leafy shoot instead of terminating a shorter leafless shoot (sometimes referred to as 'basal' in the literature), the presence of villose indumentum on most of its vegetative parts (vs. glabrous or sparsely puberulous), and a cordate (vs. acute to rounded) leaf base.
Habitat and ecology. In secondary roadside vegetation, at elevations of 150-700 m. Flowering year-round.
Etymology. This species is named "pseudospiralis", referring to its resemblance to C. spiralis.
Etymology. Costus rubineus sp. nov. is named in reference to the Spanish explorer Hipolito Ruiz who visited in August 1780 the place called Chinchao in the Peruvian department of Huánuco. In his journal, he mentioned the collection of a plant he referred to as "Costus ruber", but his collection was lost in a shipwreck off the coast of Portugal, and this species' name was never again mentioned in the journal. Since there is already a C. ruber C.Wright ex Griseb. (a synonym of C. pulverulentus C.Presl), we cannot use that name but are using the very apt name of C. rubineus to reflect the beautiful ruby-red colour of the bracts. The first author of this species visited the Chinchao region in 2016 and found at that locality specimen which he believed to be the same species as Ruiz mentioned in his journal (Skinner 2016  Notes. Costus rubineus sp. nov. is a species mostly restricted to relatively high elevations (except for Foster 8950A, which was found at 300 m) in the departments of Pasco, San Martín, and Huánuco, Peru. It looks, at first glance, somewhat similar to C. spiralis (Jacq.) Roscoe, but it differs from that species by its abaxially oriented flowers and a very short ligule. The living plants look similar to C. scaber Ruiz & Pav., but that species differs by a much shorter calyx (3-7 mm vs. 9-15 mm long in C. rubineus) and the presence of a row of erect hairs on the adaxially of the lamina (lacking in C. rubineus). There are often several flowers at the same time at anthesis, whereas in C. scaber, there is usually just one flower at anthesis. Description. Herb 0.5-0.7 m tall. Leaves sheaths 10-18 mm diam; ligule 10-20 mm long, obliquely truncate; petiole 5-15 mm long; sheaths, ligule and petiole glabrous, purple-red to green; lamina ovate-elliptic to narrowly ovate-elliptic, 22-29 × 10-13 cm, dark, olive green adaxially, red-purple to dark purple abaxially, with 5-6 dark green bands corresponding with slightly raised veins above, adaxial and abaxial surfaces both glabrous, base acute, apex acute to shortly acuminate (acumen 3-5 mm long). Inflorescence ovoid, ca. 7 × 4.5 cm, terminating a leafy shoot; bracts and appendages of bracts, bracteole, calyx, and ovary glabrous. Flowers abaxially oriented; bracts red, coriaceous, broadly ovate, 3-4 × 2-3.5 cm; appendages green, foliaceous, ascending, triangular-ovate, 2.5-5 × 2-3.5 cm, apex acute; bracteole boat-shaped, 24-30 mm long; calyx red, 12-20 mm long, lobes very shallowly triangular, 2-5 mm long; corolla white, 60-75 mm long, glabrous, lobes narrowly elliptic, 45-60 mm long; labellum white, distal edge horizontally spreading, broadly obovate, 60-70 × 50 mm, lateral lobes striped with red, middle lobe reflexed with yellow honey mark, irregularly lobulate, margin crenulate; stamen white, tinged with red, 35-40 × 13-14 mm, not exceeding the labellum, apex 3-dentate, anther 8-10 mm long. Capsule not seen.
i. Habitat and ecology. In tropical wet forests at an elevation of 250-400 m. Flowering period is uncertain.

Figure 21.
Etymology. This species has been named after its type locality El Whiskey (Putumayo, Colombia), with "cola" the Latin for "living in".
Paratypes Notes. This new species has long been widely cultivated worldwide, originally grown from seeds collected by Tim Plowman when preparing Plowman & Davis 4396 at the type locality. Until a late stage in our revision, we united this species with C. erythrophyllus Loes. Although the flowers and inflorescence look very much like those of that species, the leaves are quite different in their colour and the almost absence of distinct plication. They also have a thicker mesophil layer and are waxy in living plants. This species can also be distinguished from C. erythrophyllus by the length and shape of the ligules, which are truncate to obliquely truncate instead of being deeply lobed.   In April 2022, Dave Skinner visited the Santa Cruz private reserve of Project Amazonas near Iquitos, Loreto, Peru and found large populations of plants in primary forest that are identical vegetatively and have flowers that match those of Costus whiskeycola. However, the bracts lack leafy appendages. It is yet to be determined whether or not these plants are of this same species.