Two new species of Chlorospatha section Orientales (Araceae) from western Andes in Colombia

Abstract Two new species of Chlorospatha (section Orientales) from the western slope of the Cordillera Occidental in the departments of Valle del Cauca and Choco (Colombia) are described here. The new species represent the first records of section Orientales for Colombia, which was previously known only from the eastern Andes in Ecuador. The two new species are similar to C. longipoda, C. hannoniae and C. boosii. Chlorospatha minimasp. nov. is differentiated by its small overall size (less than 30 cm tall), blade strongly inequilateral with smooth adaxial surface, and spadix less than 2.2 cm long. Chlorospatha silverstoneisp. nov. is differentiated by its large overall size (30–60 cm tall), 1–3 leaves per plant, and quilted adaxial blade surface.


Introduction
The tribe Caladieae (Araceae) comprises 11 genera and 326 species restricted to Tropical America (Grayum 1986, Cusimano et al. 2011, Boyce and Croat 2011 and 8 species (genus Hapaline Schott) in Tropical Asia. The center of diversity of the tribe is Colombia with about 35% of the species, most of them endemic (Grayum 1986, Croat and Hannon 2015, Croat et al. 2017. The genus Chlorospatha Engl., with 68 species (Croat and Hannon 2015), is the second largest in the tribe after Xanthosoma Schott with 201 species (Boyce and Croat 2011). Morphological characters distin-guishing these two genera and others in the tribe have been conflictive (Mayo and Bogner 1988), and the phylogenetic relationships within Caladieae need to be further studied. Cusimano and collaborators (2011) included in their phylogeny only one species of Chlorospatha and recovered it as sister of Xanthosoma; however, Gonçalves (personal communication) found some species of Chlorospatha nested within Xanthosoma, using molecular data.
Until 1981, and for almost 100 years, the genus Chlorospatha was monotypic with C. kolbii Engl. as the only species described. Madison (1981) combined the genus Caladiopsis Engl. with Chlorospatha, transferred two species from Caladium and Xanthosoma into Chlorospatha, and published three new species in the genus (Croat and Hannon 2015). For the next 20 years, only six new species were described until Croat and Hannon (2004) published a revision of Chlorospatha of Antioquia, Colombia, and in 2015, a comprehensive taxonomic treatment that included the description of 39 new species, 19 from Colombia and 12 from Ecuador, one new subspecies, and four unnamed taxa. For a complete history of the taxonomy of the genus Chlorospatha see Croat and Hannon (2015).
Most species of Chlorospatha have narrow distribution ranges; furthermore, the level of endemism in Chlorospatha is the highest among the genera of Araceae in Colombia, with 43 (63%) species endemic to the country (vs. 23 [33%] endemic to Ecuador). Despite the large number of species in Colombia, fewer collections were available compared with Ecuador, highlighting the need for more botanical exploration in the country and the potential for the discovery of several new species (Croat and Hannon 2015). Croat and Hannon (2015) listed 370 collections of Chlorospatha from herbaria across the world, but they probably studied more since in the manuscript they mentioned that there are 226 collections from Ecuador, 55 from Central America, and 122 from Colombia. The collection and study, in the past three years, of ca. 70 new collections of Chlorospatha from Colombia resulted in the discovery of at least four new species; here we name and describe two new species of Chlorospatha from the western slopes of the Colombian Andes. The two new species belong to section Orientales which presents a style not expanded into a mantle, sessile stigma, and was previously, known only from the eastern slopes of the Ecuadorian Andes.

Materials and methods
We assembled a database with all collections from Croat and Hannon (2015), the TROPICOS database, and the Colombian herbaria COL, CUVC and COAH. Additionally, we reviewed all the collections missing in the most recent revision of the genus (Croat and Hannon 2015) and, between 2012 and 2018, carried out eight expeditions to Serranía de los Paraguas and six expeditions to the Anchicaya river basin, where we collected the two new species. We follow Croat and Hannon (2015) for terminology and its use in the descriptions. All measurements were made from dried herbarium material unless otherwise mentioned.

Results
Our database comprised, in total, 572 collections of Chlorospatha, representing 70 species (including the two described here), with 214 collections from Colombia, seven of them belonging to the two new species. The number of collections per species was very low, with 22 species known only from the type collection, 13 only from two, 27 from less than 10, and merely eight species known from more than 10 collections. Diagnosis. Chlorospatha minima can be distinguished from other species in section Orientales by its overall small size (less than 30 cm tall), smooth adaxial leaf surface, 1-2 inflorescences per axil, and spadix 20.4-22.8 mm long. Additionally, it differs from C. silverstonei sp. nov., the other species of this section in the western slopes of the Andes, by having three collective veins (vs. two in C. silverstonei sp. nov.), and the primary lateral (secondary) and minor veins glabrous on the abaxial surface (vs. scale-like indument).
Etimology. The epithet minima refers to the small size of this species, less than 30 cm tall, the smallest in the genus.
Distribution and ecology. Chlorospatha minima is endemic to the western slopes of the Colombian Andes in the department of Valle del Cauca. It has been found only in one locality on the old road Cali-Buenaventura at 1000 m, inhabiting humid forest and growing close to a waterfall (Fig. 1).
Conservation status. Despite more than four years of extensive field work, Chlorospatha minima is known only from one population located outside the Farallones de Cali National Natural Park, in an area frequently visited by tourists. Because the estimated extent of occurrence is less than 100 km 2 , the only population known has less than 100 individuals, and the quality of habitat is declining, C. minima could be assessed as Critically Endangered, according to the IUCN criteria (IUCN 2012(IUCN , 2017. Discussion. Chlorospatha minima belongs to section Orientales, characterized by having a stylar region lacking a mantle (Fig. 2B). However, all species in section Orientales, as recognized by Croat and Hannon (2015), are endemic to the eastern slopes of the Ecuadorian Andes, whereas C. minima and C. silverstonei sp. nov. (also described here) are endemic to the western slopes of the Colombian Andes. Chlorospatha minima is similar to C. silverstonei (see discussion under this species), C. longipoda (K.Krause) Madison, C. hannoniae Croat, and C. boosii Croat & L.P.Hannon, but it differs from these four species in having an overall smaller size, less than 30 cm tall (vs. 30-60 cm). Additionally, C. minima is the only species with smooth adaxial leaf surface (vs. quilted or bullate) (Fig. 3), cataphylls of inflorescence not visible outside the petiole sheath, and 1 to 2 inflorescences per axil (vs. 1 to 7) (Table 1).
Chlorospatha minima differs from C. longipoda in having leaves broadly triangularovate vs. narrowly ovate or ovate-elliptic, base of blade slightly hastate vs. subcordate to subsagittate, and (6)20-24 seeds per berry (vs. 7-8). It differs from C. hannoniae in having leaves weakly hastate at base vs. sagittate or subsagittate, apex of spathe apiculate vs. cuspidate, and erect spadix vs. slightly curving forward. Finally, C. minima differs from C. boosii in having 2-5 leaves that are held erect (vs. 8 to 12 leaves) (Table 1). Also, in both species described here, we observed several layers of apparently dead cells on the abaxial surface forming a reticulum visible on dried specimens (Fig. 2F-G,  2M-N). This is not mentioned on the description of other species of section Orientales; therefore this could be a potential diagnostic character.

Indument of veins in lower surface
Absent present unknown unknown unknown  Diagnosis. Chlorospatha silverstonei can be distinguished from the other species in section Orientales by having 1-3 leaves per plant, an overall larger size (30-60 cm tall) and a small spadix (25-37.3 mm long). Additionally, it differs from C. minima sp. nov., the other species in this section from the western slopes of the Colombian Andes, in having two collective veins (vs. three in C. minima sp. nov.), the primary lateral and minor veins with scale like indument on the abaxial surface (vs. glabrous).
Etimology. Chlorospatha silverstonei is named in honor of Dr. Phillip Silverstone-Sopkin (1939-2018, an American botanist who lived and worked in Colombia for 39 years. He was a faculty member at Universidad del Valle until 2014 and an ad Honorem professor since 2015. Additionally, he was the director of the herbarium Luis Sigifredo Espinal Tascon at the same University for 17 years. Dr. Silverstone-Sopkin collected more than 13000 botanical specimens, especially from the department of Valle del Cauca, and carried out several explorations in the region where this species was found. Distribution and ecology. Chlorospatha silverstonei is endemic to the western slopes of the Colombian Andes, along the border between the departments of Valle del Cauca and Chocó. It grows in cloud forests between 1900 and 2300 m. It has been collected in two natural reserves, "Cerro El Inglés" and "Alto Galapagos" (Fig. 1), where it has been found widespread in the dark understory, with high humidity and, sometimes, flooded ground. This species has been recorded flowering in October and January. Information about pollination is still lacking but we observed individuals of a species of Brachonidae (Hymenoptera) visiting the inflorescence during female anthesis.
Conservation status. Chlorospatha silverstonei has been found in two localities along the Serranía de los Paraguas mountain range, with an estimated extent of occurrence larger than 38000 km 2 . In these two localities there are several populations of this species with abundant individuals; therefore, C. silverstonei is preliminary categorized as Least Concern (LC), according to the IUCN criteria (IUCN 2012(IUCN , 2017.