On Hydrangea peruviana, an endangered species from Ecuador, and Hydrangea oerstedii, very common in Costa Rica and Panama, and seven threatened Central and South American Hydrangeas, which have been confounded with these

Abstract Hydrangea section Cornidia, currently consisting of 19 accepted taxa, occurs from Mexico to Chile and Argentina, with one species in southeast Asia. Its representatives are root-climbing lianas which may grow up to 60 m high in the tree canopy of temperate to (sub)tropical forests. Our extensive field work throughout its distribution area, study of herbarium specimens and ongoing molecular studies have resulted in the discovery of species new to science, as well as new insights into the circumscription of many taxa. We here present amended descriptions for seven Hydrangea species of Central and South America and discuss the taxonomical situation of two Colombian Hydrangeas, including an identification key, illustrations, and distribution maps. Field work was carried out in Costa Rica, Panama, Ecuador and Peru, including exploration in areas where the genus had not been collected before. These specimens and observations were complemented with the study of specimens of 41 herbaria of North, Central and South America, as well as Europe. Detailed morphological studies of all species were carried out, based on living plants in their natural habitat, as well as on dried specimens from our own collections and all available herbarium material. Type material was studied in detail for all species concerned. Based on an extensive number of morphological characters, combined with distribution patterns, phenological differences and ecological preferences, including molecular data in most cases, Hydrangea peruviana and H. oerstedii are clearly distinct taxa, as well as the other seven species mentioned here, which had been synonymized with either of these two species. The present study results in the recognition of 26 species in section Cornidia and exemplifies the urgent need for profound taxonomic studies in plants, as in many families we do not dispose of well-circumscribed units for conservation to mitigate the already occurring unprecedented loss of biodiversity.

herbarium material. Type material was studied in detail for all species concerned. Based on an extensive number of morphological characters, combined with distribution patterns, phenological differences and ecological preferences, including molecular data in most cases, Hydrangea peruviana and H. oerstedii are clearly distinct taxa, as well as the other seven species mentioned here, which had been synonymized with either of these two species. The present study results in the recognition of 26 species in section Cornidia and exemplifies the urgent need for profound taxonomic studies in plants, as in many families we do not dispose of well-circumscribed units for conservation to mitigate the already occurring unprecedented loss of biodiversity.

Keywords
Conservation, Ecuador, functional dioecism, hortensia, lianas, Neotropics, Peru, taxonomy introduction The relatively poorly known Hydrangea L. section Cornidia Ruiz & Pav. consists of 19 currently accepted taxa (18 species and one variety) and a yet undefined number of species new to science and taxa that have been erroneously synonymized. The representatives of this section occur from northern Mexico to southern Chile and Argentina with one species, Hydrangea integrifolia Hayata, in southeastern Asia Samain and Martínez Salas 2015;Samain et al. 2019). All taxa are evergreen root climbers growing up to 60 m high in the canopy of mostly primary forests, or rarely on boulders and rock walls (Granados Mendoza et al. 2014), generally functionally dioecious, rarely monoecious, with coriaceous leaves and hortensia-like whitish-, greenish-, yellowish-, reddish-or purplish-tinged inflorescences, with or without enlarged marginal flowers.
Hydrangea section Cornidia (hereafter shortened as Cornidia) is monophyletic, including the single Asian species (Samain et al. 2010;Granados Mendoza et al. 2013a, b, 2015De Smet et al. 2015), and is sister to the section Calyptranthe Maxim., consisting of Asian climbing species . Both clades together are sister to the section Asperae (Rehder) Y. De Smet & Samain, encompassing Asian shrubby species . As already noted by Samain et al. (2019), we do not follow the nomenclatural changes proposed by Ohba and Akiyama (2016), who suggest recognition of Cornidia as a segregate genus within tribe Hydrangeeae, together with most of the other sections published by De Smet et al. (2015), as they do not take into account the evolutionary context in which the new classification of the tribe Hydrangeeae was presented.
The monography of the genus Hydrangea s.s. by McClintock (1957), which is entirely based on herbarium specimens, is the only available recent complete revision of this section and includes 12 accepted species, classified in two subsections, Monosegia Briq. and Polysegia Briq. As mentioned by Samain et al. (2014), the revision by Mc-Clintock (1957) oversimplifies the high morphological variation within Cornidia in the Neotropics, due to inappropriate synonymization of taxa (since the description of Cornidia as a genus by Ruiz and Pavón (1794), more than 40 taxa have been described within this group), and to the fact that many diagnostic morphological characters were not taken into account (Samain et al. 2010(Samain et al. , 2019. Following the revision of the genus Hydrangea by Freire-Fierro (2004) for the Flora of Ecuador, who considered Hydrangea oerstedii Briq. as a variety of Hydrangea peruviana Moric. ex Ser., only eleven species were recognized before the start of our revision of the genus .
We have carried out extensive field work throughout the distribution area of Cornidia since 2009, and as a consequence, we realized that its representatives are much more common than previously known (albeit most of them are severely threatened, mainly because of habitat destruction) and that its incredible morphological variation definitely did not fit into the then eleven accepted species. However, contrary to Mexico where we have recently described seven new Hydrangea species and registered one new record of a species until then only known from Guatemala (Samain et al. , 2019, an important portion of the morpho-species in Central and South America do coincide with earlier described species which are currently considered to be synonyms. Apart from the considerable confusion over names, an additional challenge in this group is the functional dioecism, which we have observed in most individuals during our extensive field work throughout the Neotropics, and which is reflected by a notoriously different size and shape of flower receptacle, anthers and pistils between functionally female and male flowers (Samain et al. , 2019Samain and Martínez Salas 2015). Interestingly, some species do not show this functional dioecism at all (e.g., H. seemannii L.Riley which has bisexual flowers, Samain et al. 2019), whereas some others may show functionally dioecious or perfect flowers depending on the individual.
The above-mentioned issues emphasize the need for a complete and urgent revision of Cornidia, especially in the light of conservation of these species. Their pristine habitat with very specific conditions (near water, often flat topography near the plants, efficient drainage) makes them not only promising bio-indicators, but also poses an additional threat as these habitats are being destroyed because they are highly appreciated by local people for agriculture (Samain et al. 2019). Our recent publications on Cornidia focused on the Mexican species were based on 186 herbarium collections, of which 50% were collected by ourselves (Samain et al. , 2019. The present work aims at resolving the complex of nine species from Central and South American species that had been formally synonymized under Hydrangea peruviana (H. schlimii Briq., H. caucana Engl., H. durifolia Briq., H. goudotii Briq., H. oerstedii Briq., H. panamensis Standl., H. peruviana Moric. ex. Ser., H. trianae Briq. and H. weberbaueri Engl.). The main objective of the present study is to show that we are dealing with nine different species, primarily based on morphological characters, and strengthened by preliminary molecular data. The identification key which is presented here thus has no other aim than showing that these species can be distinguished with relative ease based on morphological characters that are straightforward to observe. Based on meticulous observations in the field and of herbarium specimens, we here present amended descriptions for seven Hydrangea species of Central and South America and discuss the taxonomic situation of two more species of this group, including an identification key of species as recognized here, illustrations, and distribution maps, as well as information about their diversity, their global conservation status, and their affinities with other Cornidia species.

Material and methods
Field work focused on Hydrangea has been carried out by the authors during dry and rainy seasons in Costa Rica (2012Rica ( , 2013, Ecuador (2012), Panama (2019) and Peru (2011Peru ( , 2012Peru ( , 2013, coinciding with the flowering and fruiting seasons, based on herbarium material of most of the species included. Exploring field work was not only carried out in the areas where previous collections had been made, but also in zones where Hydrangeas had not yet been recorded and where we suspected they would be present, based on our knowledge of their habitat preferences. Branches with inflorescences, flowers and fruits of all stages were collected and preserved. Moreover, in several individuals where architectural traits seemed to be important, whole branches were collected, of course without affecting the viability of the individual plants, cut and subsequently numbered in order to maintain the architecture available for further study. All specimens were deposited in local herbaria in the respective countries where we collected (CR (including INB) Thiers, continuously updated), most of them loaned, few (mainly type specimens) in high resolution on JSTOR Global Plants (https://plants.jstor.org/). A few herbaria, where loans were not allowed or logistically not possible, were visited in person to study the material in detail and take high quality photographs for later reference. A total number of 407 collections are included in this study, of which 75 have been collected by the authors of this paper. Both numbers may seem relatively low for a taxonomic revision; however, given that most of the species are rare to very rare on the one hand, and that hiking to primary vegetation followed by climbing of the host tree is required to reach inflorescences in most individuals on the other hand, these are highly representative. Indeed, as can be seen from the list of herbaria, most herbaria in the study area, as well as foreign herbaria with important collections (both recent and historical), have been consulted. Countries in the Specimens Examined section are listed alphabetically. For each specimen with reproductive structures studied, we mention whether it is functionally female (♀) or functionally male (♂), as well as which structures are present. Measurements were taken from dry herbarium specimens and three or more measurements per structure were taken when possible. Floral organ measurements were based on dry flowers. Colors were based on photographs of living plants and notes on herbarium labels. With respect to the leaf vein morphology, we use the standard terms we have used since our first treatment of this genus ) in order to provide consistency: midvein for the central vein of the leaf, primary veins for the first order veins, secondary veins for the second order veins, and tertiary veins for the third order veins. The leaf characters in the identification key refer to the large, mature leaves on the stems and not to the leaves on the inflorescence axes.
Red List categories were obtained according to the IUCN Red List criteria (IUCN 2012). All known localities, including those of herbarium specimens without coordinates, were geo-referenced using Google Earth (2020). Extent of Occurrence (EOO) and Area of Occupancy (AOO) of all species were calculated with GeoCAT (Bachmann et al. 2011). Distribution maps were obtained with the same set of coordinates using ArcGIS v.10 software by Esri (www.esri.com).

Taxonomy
The present treatment includes the Cornidia species Hydrangea oerstedii and H. peruviana, plus seven other species which had been erroneously synonymized with the former two. Amended morphological descriptions for seven of these and an identification key to the taxa treated here are provided. We do not repeat here the morphological description of the section as this has been published in an Open Access paper by Samain et al. (2019). All species included here are characterized by lateral and umbellate inflorescences with reddish to purplish marginal and reduced flowers, except for H. panamensis, which has been reported with pink, yellow or white marginal flowers; hence, the earlier confusion of all these species, although in fact they are easily distinguishable. There are other taxa with similar colors in this section, but these have never been synonymized with the two abovementioned species, although South American herbarium specimens of these taxa may also be identified as H. peruviana. These taxa will be treated in an upcoming manuscript with species surrounding Hydrangea preslii Briq.
It should be mentioned that our ongoing molecular studies in the Cornidia clade show that most of the species studied here are even not closely related, with the exception of Hydrangea panamensis and H. peruviana on the one hand, and H. goudotii and H. trianae on the other hand (Granados Mendoza 2013; Granados Mendoza et al. unpublished data). Hence, we are not treating a monophyletic group of species here. Nevertheless, given that the focus of the present paper is morphological-taxonomical, and as all nine species since the 1950s are continuously considered as H. peruviana/H. oerstedii on herbarium specimens, in revisions and treatments (McClintock 1957;Freire-Fierro 2004;Christenhusz 2009), as well as in local floristic lists and catalogues such as those of Costa Rica (Morales Quirós 2007), Ecuador (Jørgensen and León-Yánez 1999), Panama (Correa et al. 2004), and Peru (Brako and Zarucchi 1993), we consider it appropriate to show in a single treatment that we are dealing with clearly distinct taxa which deserve recognition at species level based on an extensive range of morphological characters.
Of the nine taxa treated below, we have observed six in the field throughout their distribution area. Hydrangea caucana Engl., H. durifolia Briq. and H. schlimii Briq. have not been collected recently and are known with certainty from nine herbarium specimens, the type collection and a putative additional herbarium specimen, or the type collection only, respectively. The three of them are endemic to Colombia, where we have not yet been able to collect Hydrangeas due to collection permit and export regulations.
Key to the species of Hydrangea section Cornidia which have been confused with Hydrangea oerstedii and Hydrangea peruviana, including these two species (Note: as mentioned above, this is a partial key that shows that these species are easy to distinguish. It cannot be used to identify all red-flowered Hydrangeas of Central and South America) Description. Root-climbing liana of probably not more than 15-20 m high; functionally dioecious; free-growing branches slightly quadrangular, densely pubescent with reddish brown stellate hairs; leaves decussate, petiole sulcate adaxially, terete abaxially, color reddish brown, densely pubescent with caducous, reddish-brown, stellate hairs, 0.6-1.5 cm long, leaving a semicircular scar on the branch when leaves shed; lamina flat, ovate to lanceolate-elliptic, 6-12 cm long, 2.6-5.5 cm broad, base rounded to decurrent, sometimes asymmetric, apex acuminate, leaf margin glandular dentate, teeth generally small, larger in only a few leaves, venation brochidodromous, veins 5-7 pairs, adaxial leaf side with marked midvein, primary and secondary veins lightly marked, primary veins join to form submarginal vein, sparsely pubescent with appressed, white stellate hairs, in young leaves more dense and reddish hairs, abaxially with protruding veins, primary veins sometimes alternating protruding and marked in the same leaf, dark brown green, densely pubescent with appressed stellate reddish hairs near the midvein, rest of the lamina more sparsely pubescent, acarodomatia present, numerous, consisting of a simple cavity, but often not very conspicuous as they lay hidden under the midvein pubescence, in axils of midvein and primary veins; inflorescence axis densely pubescent with persistent reddish brown, stellate hairs, more dense towards the apex, 8-21 cm long, many-ribbed, with up to 3 opposite or decussate leaf pairs and up to 3 scars of possibly kataphyll pairs below the inflorescence, deciduous, petiole 5-15 mm long, lamina 6-12.5 cm long, 2.5-5.5 cm broad, kataphylls not seen, apex of the floral axis woody, basally quadrangular, apically triangular, elongated bract scars visible, 3-4 mm broad, 1.5-2 mm high in functionally female plants, 3.5-5 mm broad, 2-2.5 mm high in functionally male plants, inflorescence bracts cucullate densely pubescent, hairs reddish-brown, stellate, increasing in size, lowermost bract 1.5 cm large, 1.2 cm broad, other bracts not visible, inflorescences lateral ( Fig. 1), decussate, 1-3 pairs of inflorescences per flowering branch, flowering branch only continues growing vegetatively rapidly during inflorescence development, with up to 6 leaf and kataphyll pairs above the inflorescences, inflorescence axes with basal lignified parts of inflorescences of previous years not seen, kataphylls at the base of the inflorescence present, orbicular, inflorescence umbellate, buds not seen, in flowering stage 4-12 cm diameter, 2.5-7 cm high, with 6-9 main axes in functionally male plants, 6-8 main axes in functionally female plants, partial inflorescences cymes, secondary and tertiary inflorescence axes densely pubescent with reddish, stellate hairs, pubescence gradually decreasing towards flower insertion; enlarged marginal flowers always present, terminally placed in a cyme, sepals 4, separate, with marked veins, pistils 2, fertile or reduced, some flowers with mature fruit, in these cases only 1 sepal visible, 1.5-2.3 cm diameter, pedicel 1-2 cm long, reddish-purple; flower pedicel of reduced flowers, 0.2-1.5 mm long in functionally male flowers, 0.5-2(-3) mm long in functionally female flowers, receptacle triangular in functionally male flowers, semiglobose in functionally female flowers, ovary inferior, calyx lobes 4, triangular in male flowers, nearly reduced to zero in female flowers, enlarging during fruit maturation, reduced, petals 4, bright red to purple, cucullate, 1.2 mm long; functionally male flowers: hypanthium 1-1.2 mm broad, 0.8-1 mm high, stamens 8, well-developed, pink, filaments 0.5-1.5 mm long, anthers 0.5 mm long, 0.2 mm broad, pistils 2, reduced, 0.2 mm long, stigmas not penicellate; functionally female flowers: hypanthium 1 mm diameter, 0.5 mm high, stamens 8, reduced, filaments and anthers together 0.2 mm long, pistils 2, 0.5-0.8 mm long, enlarging up to 2 mm during fruit maturation, stigmas slightly apically clavate and shortly penicellate; fruit a semiglobose capsule, apically with a thickened border, dark reddish brown, 0.8-1.2 mm high, 1.5 mm broad above, 1.5 mm diameter, opening between the two pistils to release seeds, seeds not seen.
Distribution. This species is endemic to Colombia and currently only known from the departments of Antioquia, Nariño and Valle de Cauca (Fig. 2).
Habitat. Hydrangea caucana is known from mountain cloud forest at elevations between 750-1365 m.
Phenology. Hydrangea caucana has been collected with flowers and fruits between November and March.
Notes. McClintock (1957) cited the K material as lectotype albeit without designating a specific sheet, which was copied by Freire-Fierro (2004). The holotype in B was destroyed; a photo of this specimen is available in F. We here select the better of the two sheets at K in a second-step lectotypification.
Hydrangea caucana should not be considered a synonym of H. peruviana and can be distinguished from the latter species by the flat, ovate to lanceolate-elliptic leaves with a glandular dentate margin. In contrast, H. peruviana is characterized by very slightly spoon-shaped, elliptic to slightly obovate leaves with a serrate to slightly dentate margin. Moreover, H. caucana is currently only known from Colombia, whereas H. peruviana is restricted to Ecuador. We have not observed this species in the field, and herbarium labels of the known specimens of H. caucana do not record the size of the plants.
The phylogenetic relationships of Hydrangea caucana are yet unknown as there was no fresh material available for our molecular study (Granados Mendoza et al. unpublished results).
Preliminary conservation status. Based on the available herbarium collections, this species is Endangered according to the IUCN categories and criteria (IUCN 2012), with an AAO of 32 km 2 , fewer than five locations and an extensive reduction in both EOO and AOO due to habitat destruction and fragmentation. The most recent collection of this species we have seen is from 1992, so further exploration is needed to know the current distribution and conservation status of this species.
Additional specimens examined. Description. The most complete description to date can be found in the treatment by Briquet (1919), pages 406-407.
Distribution. Hydrangea durifolia is known from the type and an additional collection in northern Colombia (Fig. 2).
Notes. McClintock (1957) cited the type collection at G as "holotype", but there are two specimens, as in the case of H. caucana, so we here designate a second-step lectotype with the better of the G sheets. She also mentioned the existence of a fragment and photo in F, but we have not seen these, despite a visit to this herbarium. Apart from the original syntype (Holton 661, G, with locality in the "regione neogranadinobogotana"), there is only one other specimen (see details below) that with certainty belongs to this species amongst the material we have studied for this revision. The leaves of the type specimen and of the Holton 661 specimen are part of the inflorescence, which complicates the recognition of this species, as "vegetative" leaves are important for a correct identification at species level. However, these leaves are present in the only additional specimen we could assign with certainty to this species (Fig. 3). We have noticed that we are only able to identify collections with mere inflorescences of Cornidia up to species level, after having studied many samples of a specific taxon, as the leaves on the inflorescence axis do not have easily definable species-specific characteristics in comparison with the "regular" leaves.
The herbaria COL and F each house a black and white photo of a specimen of the Linden 1393 collection, presumably taken in the BR and G herbaria, respectively.
Because of the lack of material and therefore, the uncertainty about this spe-cies´ circumscription, it is currently not possible to present an amended description. However, we also have no elements to consider this species as a synonym of one of the other species treated here, although it is morphologically close to H. oerstedii Briq. Briquet (1919) distinguished H. oerstedii by the much less coriaceous leaves, the inflorescence which has twice the width, the lax cymes as opposed to the more compact ones in H. durifolia, the sepals of the marginal flowers being two or three times larger, more papyraceous, with more abundant joined and protruding veins, which we can confirm based on the type specimens of both taxa. The few specimens of H. durifolia are known from the Colombian departments of Norte de Santander and Santander, whereas H. oerstedii is distributed in Costa Rica and Panama. Exploring field work in forests at elevations of around 2000-3000 m in the departments of Norte de Santander and Santander in the area of Pamplona might lead to the rediscovery of this species and the material will be helpful to define its taxonomic status.  The phylogenetic relationships of Hydrangea durifolia are yet unknown as there was no fresh material available for our molecular study (Granados Mendoza et al. unpublished results).
Preliminary conservation status. It is possible this species is Critically Endangered according to the IUCN categories and criteria (IUCN 2012), given its AAO of 8 km 2 , the existence of less than five locations and an extensive reduction in both EOO and AOO because of habitat destruction and fragmentation. However, we currently propose this species as Data Deficient, as its actual status is not well-known.
Additional specimen examined. Colombia. Santander: Vicinity of La Baja, 3000 m, 14-31 Jan 1927, ♂, inflorescence buds, flower buds, flowers, Killip & Smith 18366 (GH (2), NY, US) (Figs 3-4). Description. Root-climbing liana of up to 10 m high; functionally dioecious; free-growing branches many-ribbed, slightly angular to quadrangular, apically with dense appressed white caducous stellate hairs; leaves papyraceous, decussate, petiole terete, rarely slightly quadrangular or sulcate adaxially, basally with broadly sulcate adaxially, color dark green, scarcely pubescent with small, white stellate hairs, 1.5-2.7 cm long, leaving a triangular scar on the branch when leaves shed; lamina elliptic to obovate, 14-25 cm long, 7-14 cm broad, base cuneate, slightly decurrent, sometimes asymmetric, apex mucronate to acuminate, leaf margin (widely) serrate, venation brochidodromous, veins 8-9 pairs, adaxial leaf side with midvein protruding along its whole length, primary and secondary veins also protruding, angle primary veins up to 50 degrees, secondary veins reticulate and connecting the primary veins resulting in a network with parallel secondary veins nearly perpendicular with respect to the primary veins, white stellate pubescence scarce, only near the leaf base, abaxially with protruding veins, opaque olive green, scarcely to densely pubescent with appressed stellate white hairs, the latter depending on the specimen, nearly sessile to shortly stalked, acarodomatia numerous, present in axils of midvein and primary veins in the lower 2/3 of the lamina, consisting of a simple cavity, glabrous or sometimes with stellate hairs in the entrance; inflorescence axis densely pubescent with appressed, white, stellate hairs (Fig. 5B), 6-15 cm long, gradually broadening towards the apex, with 2 opposite leaf pairs along the axis and one opposite kataphyll pair immediately below the inflorescence, deciduous, petiole 1 cm long, lamina 3.5-9.3 cm long, 2.5-6 cm broad, abaxially densely pubescent with white stellate hairs, apex of the floral axis woody, cone-shaped, elongated bract scars visible, thickening at the top, 8-9 mm broad, 5-6 mm high in functionally female plants, 6-7 mm broad, 2-2.5 mm high Figure 5. Hydrangea goudotii A branch with leaves seen abaxially, old inflorescence axes and the vegetative portion of the flowering branch B inflorescence bud with cucullate inflorescence bracts and densely pubescent inflorescence axis C inflorescence of functionally male plant, with enlarged marginal flowers and a few flowers that still show stamens A field image of collection Granados Mendoza et al. 2012-105 B, C field images of collection Granados Mendoza et al. 2012-43. in functionally male plants, inflorescence bracts cucullate, dark green to light pink ( Fig. 5B), coriaceous, abaxially densely pubescent with whitish stellate hairs, margin membranous and glabrous, veins not visible as a consequence of the pubescence, bracts increasing in size distally, consecutively and rapidly deciduous during inflorescence development, inflorescences lateral ( Fig. 5C), opposite, 1-4 pairs of inflorescences per flowering branch, up to 3 decussate small leaf pairs (or their scars) between the two inflorescence pairs, flowering branch continues growing vegetatively very rapidly during inflorescence development, with already up to 4 decussate leaf pairs above the inflorescences when the upper inflorescences are still in bud, linear, with dense white stellate hairs, inflorescence umbellate, buds up to 3.4 cm broad and 3 cm high before opening, in flowering stage 5-12 cm diameter, 2.5-8 cm high, with 5-10 main axes in functionally male plants, 5-6 main axes in functionally female plants, partial inflorescences umbels, secondary and tertiary inflorescence axes with reddish-white, appressed, stellate hairs; enlarged marginal flowers always present ( Fig. 5C), terminally placed in a cyme, up to 3.6 cm diameter in female plants, up to 1 cm in male plants, sepals with marked veins, pistils 2 or sometimes not at all developed, reduced stigma not developed, receptacle rudimentary, globose, nearly the same size as that of reduced flowers, further characters not observed in detail, pedicel in male plants up to 1.5 cm; flower pedicel of reduced flowers 0.1-2.2 mm long in functionally male flowers, 1 mm long in functionally female flowers, enlarging during fruit development, 1.5 mm long in mature fruits, receptacle broadly campanulate in functionally male flowers, semiglobose in functionally female flowers, ovary inferior, calyx lobes 4, triangular, 0.3-0.5 mm long, petals 4, pinkish to wine red, imbricate, cucullate, membranous, 2 mm long, 1 mm broad; functionally male flowers ( Fig. 5C): hypanthium 1 mm diameter, 1.5 mm high, stamens 8, well-developed, filaments 1-1.5 mm long, anthers 1 mm long, 0.2 mm broad, pistils 2, reduced, 0.1 mm long, stigmas not penicellate; functionally female flowers: hypanthium 1.5 mm diameter, 1-1.5 mm high, stamens extremely reduced, as such their number could not be determined and their filaments and anthers have not been measured, pistils 2, 1 mm long, enlarging up to 1.5 mm during fruit maturation, stigmas apically clavate and shortly penicellate, 0.2 mm long; fruit a semiglobose capsule, apically with a conspicuous border, dark reddish brown, 2 mm high, 2.5 mm broad above, 3 mm long, opening between the two pistils to release seeds, seeds not seen.

Hydrangea goudotii
Distribution. Hydrangea goudotii is endemic to Colombia and Ecuador. Further exploration for this species throughout both countries is required, as its currently known distribution pattern is fragmentary.
Habitat. This species occurs in mountain cloud forest, sometimes on heavy slopes at elevations between 1000-2500 m.
Phenology. This species has been collected in flower and fruit in January, March, June, July, August, and December. Although further studies on its biology are needed, it is likely that H. goudotii is characterized by two distinct flowering and fruiting periods: December-March and June-August. However, it remains to be investigated whether these two periods take place each year. " (correct current locality names and G barcode numbers are placed between brackets). It seems all three collections are from the Central Cordillera between Ibagué and Armenia in the department of Tolima (R. Callejas, Universidad de Antioquia, Colombia, pers. comm.). McClintock (1957) selected the latter of the three syntypes mentioned in the original description by Briquet (1919) as lectotype, although she referred to it as holotype which is not correct according to the ICN (Art. 9, Turland et al. 2018). However, as in several other species for which McClintock (1957) realized lectotypifications and synonimizations, we doubt that she actually has had access to the involved specimens. In the case of H. goudotii, she considered the most representative specimen to be the collection which has been fragmented to take material to the herbarium F. Indeed, the specimen in F [F0066624F] consists, apart from the fragments of leaves and inflorescences, of a photo of the original Goudot collection. Careful examination of the latter shows that it consists of the branch which was designated as lectotype by McClintock (1957) [G00418961], which has been turned around 180 degrees, and an additional branch which was fragmented and is the F specimen. The latter is considered as isolectotype in that herbarium. However, because of the fragmentation of the original collection, the material that remained in G does lack fully developed enlarged marginal flowers.
Hydrangea goudotii should not be considered a synonym of H. oerstedii or H. peruviana var. oerstedii from which it can be distinguished by the appressed white caducous stellate pubescence on free-growing branches, these being glabrous in H. oerstedii. Moreover, H. goudotii is currently only known from Colombia and Ecuador, whereas H. oerstedii occurs in Costa Rica and Panama.
According to our molecular study, Hydrangea goudotii is closely related to H. trianae (Granados Mendoza et al. unpublished results).
Preliminary conservation status. Although this species has an EOO of about 154,700 km 2 , it is Endangered according to the IUCN categories and criteria (IUCN 2012), with an AAO of 100 km 2 , as well as an extensive reduction in both EOO and AOO due to habitat destruction and fragmentation.
Distribution. Hydrangea oerstedii is very abundant in Costa Rica and Panama. It is the most common species of this study (Fig. 8).
Habitat. This species occurs in mountain cloud forest at elevations between 1100 and 2500 m. In contrast to most of the other Hydrangea species, it is common to find this species in disturbed habitats, even when there is no primary forest left and only the very humid microhabitat and protection against direct sunlight remain.
Phenology. This species has been collected with flowers and fruits throughout the year. Notes. Not to be considered as a variety of H. peruviana, from which it can be distinguished by the flat, ovate to lanceolate-elliptic leaves with white pubescence abaxially and a glandular dentate margin. In contrast, H. peruviana is characterized by very slightly spoon-shaped, elliptic to slightly obovate leaves with reddish pubescence adaxially and a serrate to slightly dentate margin. Moreover, H. oerstedii is a relatively common species in Costa Rica and Panama, whereas H. peruviana is a very rare species from Ecuador. Freire Fierro (2004) also mentioned the presence of an isotype in K, but although this specimen bears the same locality data on its label as the type, it cannot be confirmed that it concerns the same collection, given that no number is mentioned.
According to our molecular study, Hydrangea oerstedii is not related to any of the species included in this study (Granados Mendoza et al. unpublished results).
Preliminary conservation status. With an EOO of slightly more than 20,760 km 2 and an AAO of 428 km 2 , this species is Near Threatened according to the IUCN categories and criteria (IUCN 2012). Although its habitat is continuously being destroyed and fragmented, this species is robust, and basically only needs a host tree that remains of the primary forest. As the older plants bend downwards and often have their eye-catching inflorescences just a few meters above ground level, it is even possible that this species is favored when trees are being logged. Nevertheless, should large areas of forest be destroyed, this species may well enter into a threatened category.
Distribution. This species is known from Costa Rica and Panama (Fig. 8).
Habitat. Hydrangea panamensis grows in tropical rainforest between 200 and 1000 m elevation. It usually occurs near water streams at lower elevations. Of all the species of the present study, this is the one that grows at the lowest elevation.
Phenology. Hydrangea panamensis has been collected with flowers and fruits between June and September.
Notes. Not to be considered a synonym of H. peruviana from which it can be distinguished by the rounded leaf apex with a very small acumen and the very few acarodomatia (0-2/leaf ) on the abaxial leaf side vs. the acute to acuminate, rarely mucronate leaf apex and the many acarodomatia (present in both axils of midvein and primary veins and those of primary and secondary veins) of H. peruviana. Moreover, their known distribution areas are far away from each other, with H. panamensis only growing in Central America and H. peruviana being endemic to Ecuador.
The label of the specimen Gentry 5569B mentions that the flowers are red, whereas the label of the specimen Mori & Bolten 7674 says "summit of ovary of fertile flowers reddish-pink". It seems there is some color variation in this species in both the marginal and reduced flowers. Both flower types are generally white, and this is also the color we have observed in the field ourselves.
According to our molecular study, Hydrangea panamensis is closely related to H. peruviana (Granados Mendoza et al. unpublished results).
Preliminary conservation status. Although this species has an EOO of about 50,123 km 2 , it is Endangered according to the IUCN categories and criteria (IUCN 2012), with an AAO of 60 km 2 , as well as an extensive reduction in both EOO and AOO as a consequence of habitat destruction and fragmentation. Description. Root-climbing liana of up to 30 m high, up to 20 cm diameter, functionally dioecious; leaves decussate, coriaceous, petiole sulcate adaxially, clasping its branch, color reddish brown, densely pubescent with partially caducous, reddish simple and stellate hairs, 0.5-2 cm long, leaving a semicircular scar on the branch when leaves shed; lamina very slightly spoon-shaped (Figs 9C, 10A, B), elliptic to slightly obovate, 7.5-12.8 cm long, 4.2-5.4 cm broad, base rounded to decurrent, sometimes asymmetric or very slightly cordate, apex acute to acuminate, rarely mucronate, leaf margin serrate to slightly dentate, venation brochidodromous, veins 6-10 pairs, adaxial leaf side with midvein and primary veins slightly protruding secondary veins marked, primary veins join to form submarginal vein, pubescent with small, stellate whitish pubescence, abaxially with protruding midvein and primary veins, sometimes with a few smaller less visible primary veins between the clearly visible primary veins, marked secondary veins, secondary and tertiary veins forming a reticulate network, connecting the primary veins, reddish brown, pubescent with small, stellate reddish hairs, especially on the veins, young leaves densely pubescent, acarodomatia numerous, present in axils of midvein and primary veins as well as axils of secondary veins, veins broadening  Mendoza et al. 2012-112. the acarodomatia, consisting of a cavity, rarely with hairs; inflorescence axis densely pubescent with brownish stellate hairs (Fig. 11), 7-12 cm long, broadening towards the apex, with 3-4 opposite or decussate leaf or kataphyll pairs below the inflorescence, generally not deciduous, petiole 2-4 mm long, adaxially sulcate, lamina nearly orbicular to obovate, 1.3-4.2 cm long, 1.2-2.8 cm broad, densely pubescent, scars of 2 pairs of kataphylls present, apex of the inflorescence axis woody, cone-shaped, slightly quadrangular, elongated bract scars visible (Fig. 11), narrower at the top, 4-5 mm broad, 2-3 mm high in functionally female plants, male inflorescences not seen; inflorescence bracts not seen, inflorescences lateral, opposite, 1 pair of inflorescences per flowering branch, sometimes only one inflorescence developing (Fig. 10A,B), flowering branch continues growing vegetatively very rapidly during inflorescence development, including additional branching, with up to 5 leaf pairs above the inflorescences and below the first branch, with kataphylls opposite the branches, with dense reddish stellate hairs, inflorescence umbellate, buds not seen, in flowering stage 4.5-10 cm diameter, 4-7 cm high, 3-7 main axes in functionally female plants, partial inflorescences cymes, secondary and tertiary inflorescence axes with dense reddish stellate hairs; enlarged marginal flowers always present (Figs 10-11), terminally placed in a cyme, 1.5-2 cm diameter, sepals 1-4, sepals with marked veins, remnants of 2 pistils visible, further characters not observed in detail, pedicel 1.2-2.4 cm long; male flowers not seen, (0-)1-1.5(-2) mm long in functionally female flowers, receptacle semiglobose in functionally female flowers, ovary inferior, calyx lobes 4, triangular, papyraceous, 0.25 mm long, 0.25 mm broad, petals not seen; functionally female flowers: hypanthium 1.5 mm broad, 1 mm high, 8 well-marked ribs, stamen scars visible but too small to detect a number, pistils 2, 0.2-0.3 mm long, enlarging up to 2-2.5 mm during fruit maturation, stigmas apically clavate and shortly penicellate; fruit a semiglobose capsule (Figs 10, 11C), apically with a revolute border, dark reddish brown, 1.5 mm high, 2 mm broad above, 3 mm diameter, opening between the two pistils to release seeds, seeds not seen.
Distribution. Hydrangea peruviana is a rare species which is known from Ecuador only (Fig. 6). Apart from the type collection, it is only known of six collections since 1980, two of which were realized during the explorations in the framework of our revision of the Neotropical Hydrangeas. It was found in a primary mountain cloud forest flowering very high (about 30 m) in the tree canopy. The cloudy environment Figure 11. Hydrangea peruviana. Infructescence with young fruits and densely pubescent apex of the inflorescence axis. Field image of collection Granados Mendoza et al. 2012-112. in combination with the height at which the specimens were flowering made them very difficult to spot, potentially being the reason why this species has been so rarely collected by botanists.
Habitat. This species has been reported in rainforest and cloud forest at elevations between 682 and 1300 m.
Phenology. This species has been collected with flowers and fruits in March and July. Only female plants have been observed. There are no collections known of male individuals.
Notes. Since the revision by McClintock (1957), most of the species mentioned in this paper had been lumped in H. peruviana. Following the treatment of the genus Hydrangea for Ecuador by Freire-Fierro (2004), H. oerstedii was reduced to a variety of H. peruviana, consequently all species of the present study belonged to what was until recently considered as a species complex. However, based on our extensive study of herbarium specimens, including type material, and field observations, it became clear that H. peruviana is a very distinct taxon which can easily be recognized by the densely pubescent reddish brown leaves with an acute to acuminate, rarely mucronate, apex, a serrate to slightly dentate margin and many characteristically shaped acarodomatia.
In contrast to what might be expected because of its name, H. peruviana is not known from Peru, the type locality area of Guayaquil now being the second largest city of neighboring Ecuador, and this country´s main harbor. However, at the time of its collection in the late 18 th century, modern-day Peru and most of Spanish-ruled South America belonged to the Viceroyalty of Peru.
As mentioned by Macbride (1938), it is generally accepted that their collections in the area that correspond with present-day Ecuador were not realized by Spanish botanists Ruiz and Pavón, but by their collaborator Juan José Tafalla.
According to our molecular study, Hydrangea peruviana is closely related to H. panamensis, the two of them unrelated to the other species of this study (Granados Mendoza et al. unpublished results).
Preliminary conservation status. Although this species has an EOO of about 13,515 km 2 , it is Endangered according to the IUCN categories and criteria (IUCN 2012), with an AAO of 20 km 2 , less than five locations, as well as an extensive reduction in both EOO and AOO because of habitat destruction and fragmentation. Description. The most complete description to date can be found in the treatment by Briquet (1919), pages 400-401.
Distribution. This species is currently known from the type locality in Colombia only (Fig. 2).
Notes. This species concerns a very distinct taxon with more enlarged "marginal" flowers than any other member of Cornidia. In fact, from the type specimen it seems that most flowers possess enlarged sepals. It is only known from its type collection made around 1850 and to our knowledge has not been collected since. It cannot be excluded that it concerns a local "mophead" mutation, but in the absence of recently collected material and as the leaf morphology of the type specimens cannot be matched with better-known species, we decide here to recognize this taxon as a distinct species, although we cannot present an amended description at this time, given that we only dispose of the type specimen, which already was given an excellent description by Briquet (1919).
As in the case of H. durifolia, exploring field work in forests around Ocaña in the Colombian department of Norte de Santander might lead to the rediscovery of this species, which will be helpful to define its taxonomic status.
McClintock (1957) cited as "holotype" the collection in G, which we have not been able to locate. Based on the many enlarged marginal flowers and the inflorescence leaf morphology, this species should not be considered a synonym of H. oerstedii.
The phylogenetic relationships of Hydrangea schlimii are yet unknown as there was no fresh material available for our molecular study (Granados Mendoza et al. unpublished results).
Preliminary conservation status. We currently propose this species as Data Deficient (DD), as its taxonomic status in unclear, it is only known from the type locality, and no recent collections are available.  Root-climbing liana of up to 20 m high, functionally dioecious; free-growing branches many-ribbed, slightly angular, old branches quadrangular, with erect, white stellate hairs (Fig. 13A); leaves decussate, petiole terete, sometimes abaxially flattened, color dark green, sometimes drying black, pubescent with small, erect, whitish to yellowish stellate hairs, 1.5-4 cm long, leaving a semicircular scar on the branch when leaves shed; lamina spoon-shaped, obovate to elliptic, (slightly) asymmetric, coriaceous, 15-29 cm long, 8.5-18 cm broad, with varying length-width ratios, base cuneate, acute or decurrent, apex rounded to acuminate, leaf margin (slightly) dentate, venation brochidodromous, veins 8-9 pairs, adaxial leaf side with protruding midvein and primary veins, secondary veins slightly protruding, primary veins join to form submarginal vein, dark green, slightly pubescent with white stellate hairs, especially near the margin, abaxially with protruding veins, midvein notoriously protruding, opaque olive green, pubescent with stellate white hairs, primary veins branching towards the margin, ending in a submarginal vein very near the margin, secondary and tertiary veins forming a reticulate network, connecting the primary veins, acarodomatia numerous, consisting of an often small simple cavity in axils of midvein and primary veins, sometimes covered by a membrane; inflorescence axis in the axils of kataphylls of 1-1.4 cm long or fully grown leaves, pubescent with erect, white, stellate hairs (Fig. 13C), 6-25 cm long, many-ribbed, with 2 opposite rapidly shedding leaf or kataphyll pairs along the axis, petiole of the leaves 5-10 mm long, lamina obovate to lanceolate, (slightly) asymmetric, 2-7 cm long, 1.4-4.3 cm broad, margin glandular dentate, small, appressed, stellate, abaxially and adaxially with white hairs along the midveins, similar pubescence between the veins but not appressed and larger, veins 6 pairs, all protruding, in the case of kataphylls, these initially protecting the small inflorescence buds (Fig. 13A), followed by elongation of the axis occurring between the kataphylls and the inflorescence bud, apex of the inflorescence axis woody, quadrangular, elongated bract scars visible, thickening at the top, 7-8 mm broad, 2 mm high in functionally female plants, 6-7 mm broad, 2-3 mm high in functionally male plants, inflorescence bracts cucullate, dark green, coriaceous, abaxially (densely) pubescent with small, erect, whitish and yellowish stellate hairs, inflorescences lateral, opposite, 1-2 pairs of inflorescences per flowering branch, flowering branch continues growing rapidly during inflorescence development, with up to three decussate leaf pairs above the inflorescences, with appressed, whitish and yellowish stellate hairs, dense when young, rapidly shedding, inflorescence axes with basal lignified parts of inflorescences of previous years visible in well-collected specimens, allowing to observe growth and flower periodicity, these rests 2.5-5 cm apart, 7 cm when inflorescence originate in the axils of the regular leaves, with none or one decussate leaf pair (or the scars of these leaves) in between, inflorescence umbellate, buds up to 4 cm broad and 4.5 cm high before opening, in flowering stage 7-19 cm diameter, 4-12 cm high, with 5-9 main axes in functionally male plants, 4-8 main axes in functionally female plants, partial  Samain et al. 2011-067. inflorescences dichasia, secondary and tertiary inflorescence axes with whitish and/ or reddish stellate hairs; enlarged marginal flowers generally present (but e.g. absent in Samain et al. 2011-064) (Fig. 13B), terminally placed in a cyme, 1.8-4 cm diameter, sepals with marked palmate veins, fully separated or fused at the base, sometimes one or two reduced or even absent, pistils very rudimentary, pedicel 1-3.5 cm long; flower pedicel of reduced flowers 1-2 mm long in functionally male flowers, 1-5 mm long in functionally female flowers, receptacle semiglobose in functionally male flowers, broadly semiglobose in functionally female flowers, ovary inferior, calyx lobes 4, triangular, translucid, 0.2-0.5 mm long, 0.6-1 mm broad, petals 4, adaxially red, abaxially purple with white margin, valvate, cucullate with a small mucron at the apex, coriaceous, 1.5-3 mm long, 1-1.5 mm broad; functionally male flowers (Fig. 13C): hypanthium 1.5-2 mm diameter, 1.5 mm high, stamens 8, well-developed, filaments 1.2-2 mm long, anthers 1-1.5 mm long, 0.5-1 mm broad, purple, pistils 2, very reduced, 0.5 mm long, stigmas not penicellate; functionally female flowers (Fig. 13D): hypanthium 1.2-2.2 mm diameter, 1.5 mm high, stamens 8, very reduced, filaments 0.2-0.5 mm long, anthers 0.2-0.4 mm long, 0.1-0.2 mm broad, pistils 2(-3), 1.5-2 mm long, broad at the base, narrower in the middle and broadening towards the apex, enlarging up to 3.2 mm during fruit maturation, stigmas apically clavate and shortly penicellate, 0.5 mm long; fruit a semiglobose capsule, apically with a conspicuous border, dark reddish brown, 2.5 mm high, 4-4.5 mm broad above, 3-4 mm diameter, the part around the pistils thickening upwards up to 1 mm during fruit maturation, opening between the two pistils to release seeds, seeds not seen.

Hydrangea trianae
Distribution. Hydrangea trianae is a widespread species occurring in Colombia, Ecuador and Peru (Fig. 14).
Habitat. Hydrangea trianae is known from cloud forest and remnants of this vegetation type at elevation between 400-3680 m. Moreover, it has been noted to occur in disturbed or late secondary forests.
Phenology. This species has been collected with flowers and fruits throughout the year. Notes. Hydrangea trianae should not be considered a synonym of H. peruviana, from which it can be distinguished by the notoriously coriaceous leaves, the abaxial reticulate network of secondary and tertiary veins connecting the primary ones, and the abaxial white pubescence.
Hydrangea lehmannii was synonymized with H. peruviana by McClintock (1957), whereas she considered H. platyphylla as a synonym of H. oerstedii.
With respect to the type material of Hydrangea lehmannii, McClintock (1957) cited the K material as an isotype, albeit without designating a specific sheet, and this was also cited by Freire-Fierro (2004).
With respect to the type material of H. platyphylla, McClintock (1957) cited G material as holotype, which effectively lectotypified the name. However, there are two specimens of this collection in G, therefore requiring second-step lectotypification, which is done here.
One of the F specimens (V0066626F), which supposedly is an isotype of H. platyphylla, does not belong to this species based on leaf venation, probably due to a labeling error; however, it is not possible to propose any other identification as the material is very limited. Briquet (1919) distinguished H. trianae and H. platyphylla based on leaf shape and venation, as well as size of cymes, sepals of enlarged marginal flowers and styles, which can be contributed to the sex of the single collections of both species he used for his descriptions, the specimens of H. trianae being functionally female and the ones of H. platyphylla which are functionally male.
The specimen of Triana 4668 in NY does not correspond with H. trianae or any of the other species treated here, in contrast with the specimen with the same number in COL. Triana's numbers do not correspond to field collection numbers as currently used, but instead are generic numbers based on the Endlicher system (Kirkbride 1982;Aymard 2017).
According to our molecular study, Hydrangea trianae is closely related to H. goudotii (Granados Mendoza et al. unpublished results).
Distribution. Hydrangea weberbaueri is known from Colombia, Ecuador and Peru (Fig. 14).  Samain et al. 2011-068. Habitat. This species grows in tropical rainforest and mountain cloud forest at elevations between 974-3500 m.
Phenology. This species has been collected with flowers and fruits throughout the year. Vernacular names and use. The following vernacular names are indicated on the specimen Ellemann 75381 (AAU, LOJA, MO, QCA): bejuco matapalo (Spanish), yura huanutic caspic (Quichua). Its use as fuel wood is also indicated on the label of these specimens. This is the only species of this study of which vernacular name and use have been recorded.
Notes. Not to be considered a synonym of H. peruviana from which it can be distinguished by the notorious regular venation pattern with primary veins and secondary veins parallel to each other, all of them arching towards the apex.
No duplicate material of the original type collection has been located in the herbarium MOL of the Universidad Nacional Agraria La Molina in Lima, Peru, nor any other herbarium where we have searched. The fragment held in F that is the obligate lectotype is fragmentary and does not have the diagnostic features of this taxon, therefore we designate an epitype here for diagnostic purposes. The epitype specimen was collected approximately 8.5 km south of the original type location, which at the time of our field work was the nearest location to Cheto with primary forest. Unfortunately, satellite images (Google Earth 2020) show that the forest where the epitype has been collected was destroyed for land use change less than five years after our visit.
A Weberbauer collection with the same number as the original type is present in the herbarium USM, but this is an entirely different species (with branched inflorescences) which does not belong to this group. The label on the USM specimen is not the original Weberbauer label, suggesting this represents a labeling error.
The leaf venation in the specimens from Colombia does slightly differ from that in the material from Ecuador and Peru, although it is still very recognizable. Therefore, we decided to include these in H. weberbaueri, although future studies on Colombian hydrangeas may well show it concerns a distinct and new species.
According to our molecular study, Hydrangea weberbaueri is not closely related to any of the species mentioned here, but it occurs in a clade which is sister to the one with H. goudotii and H. trianae (Granados Mendoza et al. unpublished results).
Preliminary conservation status. Although this species has an EOO of nearly 660,000 km 2 , it is Endangered according to the IUCN categories and criteria (IUCN 2012), with an AAO of 224 km 2 , as well as an extensive reduction in both EOO and AOO resulting from severe habitat destruction and fragmentation.
As a result of our study, the number of accepted species in Cornidia currently totals 26. A complete key for morphological identification of all Neotropical species can currently not be provided as the species we have not yet treated (with the exception of this study, and those by Samain et al. 2014Samain et al. , 2019 are not yet well-defined at continental scale.

Classification of species in Hydrangea section Cornidia
In his otherwise excellent revision of the then known species of Cornidia, including the description of 11 new species in the section, all unusually elaborate for that time, Briquet (1919) classified all species in two subsections, each with their respective series: subsection Monosegia Briq, with series Speciosae Briq. and Aphananthae Briq., and subsection Polysegia Briq. subdivided in series Synstyleae Briq. and Chorystyleae Briq. Subsection Monosegia, according to Briquet (1919), is characterized by a single pseudoumbellate cyme, and its series by the presence or absence of "sterile flowers", respectively (these flowers are not sterile, but have enlarged sepals; hence, we prefer the term "enlarged marginal flowers", see Samain et al. 2014). Subsection Polysegia, again according to Briquet (1919), can be recognized by the thyrsoid inflorescence consisting of several pseudo-umbellate cymes and its series amongst others by short stamens and pubescent leaves, and long stamens and glabrous leaves, respectively. Although the morphological classification in subsections at first sight may seem valid, several specimens of different species we have observed both in the field and in herbarium collections show both inflorescence types (single clusters in the axil of a leaf vs. several clusters on a branched inflorescence), indicating that these subsections are not natural, which is also reflected by our ongoing molecular work (Granados Mendoza 2013; Granados Mendoza et al. unpublished results). With respect to the series of subsection Monosegia, we have observed that, although the enlarged marginal flowers generally characterize specific species, they may also be absent in some individuals of those species (although this is not the case in the species studied here), or they may be present, reduced in size or parts, or not reduced, in species that generally do not possess them. With respect to the series of the subsection Polysegia, the first character is the stamen length, but this seems very artificial, as this distinguishes both sexes within a dioecious species: stamens in male individuals have long filaments, whereas these are short in female individuals. Hence, it may be hypothesized that this classification seemed workable based on the relatively few specimens Briquet (1919) had access to at the time, but current morphological observations of an extensive number of specimens, as well as molecular data of a representative number of these, show that this is not the case. Based on our currently available data, we do not have sufficient elements to subdivide Hydrangea section Cornidia into subsections (Granados Mendoza et al. unpublished results).

Growth form controversies
A surprisingly high number of herbarium labels of the specimens studied here, as well as some references (e.g., Christenhusz 2009), mention growth forms such as hemiepiphytic shrubs, hemiepiphytic lianas, hemiepiphytic trees, epiphytes, shrubs, trees, climbing shrubs, parasitic shrubs or trees, etc. To our knowledge, and according to our observations in the field, all representatives of Cornidia are root-climbing lianas. When the base of their stem or their host tree is damaged or cut, they will die very soon because of lack of water and nutrients (personal observations), and lack of support, respectively. This stresses the importance of precise field observations for a correct interpretation of plant habits.

Distribution patterns
Of the nine species mentioned above, five are relatively widespread, whereas four have a relatively to very restricted distribution. On the one hand, the taxonomic and conservation statuses of two endemic Colombian species, H. durifolia and H. schlimii, are not completely clear in the absence of more and/or recent collections. A third species, H. caucana, endemic to Colombia as well, also does not have recent collections, but the existing ones do allow to understand its distribution pattern in the western cordillera. The fourth species with a restricted distribution is H. peruviana from Ecuador. On the other hand, H. oerstedii is the most widespread species studied here, known from more than 150 collections from Costa Rica and Panama. Despite the fact that this species grows in montane cloud forest, which is seriously being reduced throughout is whole distribution area (see Bruijnzeel et al. 2010), it seems to be very resilient against disturbance, as we have often observed it along roads and near villages, since it basically only needs its host tree to persist. As it is one of the few Hydrangea species that bends downwards with age and because of its conspicuous inflorescences, it may even be favored by local people. Hydrangea panamensis, which also is restricted to Costa Rica and Panama, is much less common than H. oerstedii (known from 17 collections only) and grows in tropical rainforest. Hydrangea goudotii and H. trianae are yet two other species described from Colombia. The present study confirms that both extend southwards into Ecuador, and the latter one also into Central Peru, being the most widespread species of this group in South America (known from 109 collections). Finally, Hydrangea weberbaueri, described from northern Peru, is shown here to have a continuous distribution from northern Ecuador to northern Peru, with a few collections from central Peru and from northeastern Colombia. The latter, as mentioned above, differ slightly from the southern ones, but can still be referred to this species based on the peculiar leaf vein patterns.
The overall distribution area of the species studied here is from northern Costa Rica to central Peru, which is the area with the highest diversity of Neotropical Hydrangeas, apart from Mexico (Samain et al. , 2019. The few specimens of the countries north of Costa Rica and south of Mexico (Guatemala, Honduras, El Salvador and Nicaragua) belong to the widespread Hydrangea albostellata Samain, Najarro & Martínez  or remain unidentified because of a lack of fertile material, but definitely do not show affinity with the group studied here. Similarly, the few fertile specimens from Venezuela do have white flowers and belong to a group we will be treating in an upcoming study. The few specimens collected southwards of the Selva Central in Peru are generally also morphologically distinct. From both this study and ongoing morphological work in Cornidia, it becomes clear that especially Colombia needs to be further explored with respect to Hydrangea, as the record in this country seems very fragmentary and several species are known from very few collections or their type locality only.

Impact of taxonomic studies on conservation actions
Although a few populations of most of the species studied here do occur in protected areas, their long-term conservation is seriously compromised because of the significant threats from which their habitats suffer throughout their distribution area, related to fragmentation, land use change and climate change. Moreover, it is likely their dioecism makes these species even more prone to local extinction because of habitat destruction and fragmentation, as female and male individuals generally do not occur near each other, and their functional biology is not well-understood to date. During our field work, especially in Peru, where Hydrangeas often occur on private properties, in contrast with e.g. Costa Rica and Panama, where many collections were made in areas protected at national level, we have tried to sensitize the land-owners about the uniqueness of this group as a whole. Derived of the current contribution, we will also be able to do so at species level, which is especially important for the threatened taxa.
Finally, it is difficult to believe -though not surprising taking into account our recent discoveries of seven new species in Mexico (Samain et al. , 2019) -that one species, of which we now know it is extremely rare (H. peruviana), was considered to encompass eight other taxa which can be recognized by distinctive and species-constant characters, either at the varietal level (H. oerstedii), or as synonyms of the typical variety or of var. oerstedii. Moreover, if we look at global biodiversity databases such as GBIF, the situation is even worse, as the majority of the known specimens of the whiteflowered H. seemannii, endemic to northwestern Mexico, and several species of Central America, northern South America, Peru and Bolivia are also identified as H. peruviana, whereas this species is endemic to Ecuador. This latter situation calls for a more critical use of such database information, as e.g., when preparing a distribution map of H. peruviana with GBIF data in GeoCAT (Bachmann et al. 2011) for the purpose of an IUCN Red List assessment, one might come up with an Extent of Occurrence (EOO) of nearly 12 million km 2 based on 599 occurrence points reaching from Canada to Bo-livia, whereas the correct EOO is 13,515.020 km 2 only, based on 7 verified occurrence points in Ecuador. Even the combined EOO of all species of this study does not total 2 million km 2 . As a consequence, the present study exemplifies the urgent need for more interest for profound taxonomic studies in plants in general and funding to carry these out; though intrinsic costs are not high, these studies are very time-consuming, as in many plant families we do not dispose of well-circumscribed units for conservation to mitigate the currently occurring unprecedented loss of biodiversity.