Valeriana rudychazaroi can be distinguished from all the known species of the genus by its epiphytic habit on trees of Quercus glabrescens Benth. (vs. herbs, shrubs, subshrubs, small trees or climbing vines in the rest of the genus). It is morphologically similar to V. naidae Barrie and V. subincisa Benth., from which it differs by having thinner stems (0.25–0.6 cm vs. up to 2 cm in diameter in both species), leaves elongately spatulate (vs. ovate to elliptic or narrowly ovate to elliptic, respectively), inflorescence corymboid (vs. paniculoid in both species), inserted stamens in flowers (vs. exserted in both species), different shape of fruits (ovate vs. oblong to lanceolate in both species) and longer fruits (3–5 mm vs. 2–3 mm in both species).

Mexico. Veracruz: Municipio Tlacolulan, Cerro de la Magdalena, 19°43'21"N, 96°59'09"W, 2900–2950 m elev., 20 September 2020, fl., fr., R. Carral-Domínguez & M. Cházaro-Basáñez 766 (holotype: XAL!).

Perennial gynodioecious epiphyte , growing on branches of Quercus glabrescens, 45–80 cm tall. Roots fibrous. Stems terete, decumbent, 20–45 × 0.25–0.6 cm, branched in the basal portion, glabrous until the insertion of the central axis of the inflorescence, where is shortly pubescent with trichomes simple, trichomes up to 0.5 mm long. Leaves cauline and clasping, simple, opposite and decussate, persistent near the inflorescence, deciduous in late phenophases, elongately spatulate, 5.7–10.8 × 0.6–2.1 cm, apex obtuse, base largely decurrent 1.5–3.5 cm long, slightly canaliculate, margin entire, one main nerve, slightly conspicuous on adaxial surface, prominent on abaxial surface, glabrous on both surfaces and margins. Inflorescence terminal, corymboid, dichotomously divided, each terminal corymb scorpioid without rotation, being less developed one of the lateral sides, 17–24 × 13–25.5 cm from the first division to the top and considering the lateral extremes of the inflorescence, main axis 10.1–21 × 0.11–0.25 cm measured from the base until the first bifurcation. Secondary axes 2, 2.9–6.0 × 0.05–0.2 cm, tertiary axes 4, 0.33–034 × 0.1 cm, decreasing dimensions as dichotomies increase, 31–85 flowers and less than five mature fruits per terminal corymb. Bracts narrowly lanceolate to lanceolate, 2.0–2.9 × 0.45–0.8 cm, base cuneate, apex acute, margin entire, glabrous, one main nerve. Bractlets of first division linear, longer than the fruits, 0.7–0.8 × 1–1.5 mm, base narrowly clasping, apex acute, margin entire, glabrous. Bractlets of corymbs linear, equal or shorter than the fruits, 1.5–5 × 0.5–0.8 mm. Staminate flowers white, 1.5 × 0.5 mm, calyx reduced, glabrous, corolla infundibuliform, tube 2–2.7 × 2 mm (opened), 5-lobed, corolla lobes elliptic to widely triangular, 0.5–0.8 × 0.4–0.5 mm, internally and externally glabrous, stamens 3, 1 mm long, adnate to the corolla in the middle of the length, anthers globose, 0.5–0.8 mm long, bithecal, glabrous; pistilodium 1.6 mm long, included, glabrous. Pistillate flowers white, 2 × 0.7 mm, calyx reduced, glabrous, corolla infundibuliform, tube 1.0–2.2 mm long, 5-lobed, corolla lobes orbicular, 1 mm in diameter, main style 2.7–5 mm long, exserted, glabrous; secondary styles reminiscent, inserted near 1/3 corolla length. Fruit a cypsela, ovate, 12 plumose limbs derived from calyx, 3–5 × 1–1.3 mm, with 3 veins on the abaxial side 1 on the adaxial side and 2 along the margins, glabrous on all surfaces (Figs 1–3).

Figure 1. 

Valeriana rudychazaroi Cházaro, Franc.Gut. & J.R.Carral. A habit of flowering branch B staminate flower C fruit. Drawn from the holotype Carral-Domínguez & Cházaro-Basáñez 766 (XAL). Illustration by Gerardo Andrade–Quintos.

Figure 2. 

Valeriana rudychazaroi on Quercus glabrescens trees in the field. Photograph taken by Rodrigo Carral-Domínguez.

Figure 3. 

Valeriana rudychazaroi in the field. A habitat at an altitude of 3–6 m on Quercus glabrescens trees B detail of inflorescence with flowers and fruit C hosts in cloud forests from central Veracruz, Mexico. Photographs taken by Rodrigo Carral-Domínguez.

Flowering and fruiting recorded only in September.

Valeriana rudychazaroi is only known from the type locality in cloud forests from central Veracruz in eastern Mexico (Fig. 4). There are no specimens deposited in major Mexican herbaria because of the rarity of the individuals and the difficult access to the branches of the hosts. The first collections of the species (previous to 2017) have been lost due to the death of Miguel Cházaro. During one decade of botanical explorations in the Cerro de la Magdalena Mountain and adjacent regions for floristic inventories and species descriptions (Lascurain–Rangel et al. 2017; Francisco-Gutiérrez et al. 2023a), very few specimens have been found and collected in the same locality of the type, some of them preserved as sterile material. The new species grows on very tall Quercus glabrescens (Fagaceae) trees, at altitudes of 3–6 m. It is distributed in the remnants of very humid pine-oak forests at elevations from 2,900 to 2,950 m. This species inhabits a zone of cloud forests on cliffs with strong winds rising from the Sierra de Chiconquiaco, Veracruz. The Sierra de Chiconquiaco is a biodiverse basin, home to 3016 species, the type localities of 72 species and 36 endemic species (Castillo–Campos et al. 2005; Lascurain-Rangel et al. 2017). The species is only known from the Volcán de la Magdalena Mountain in Tlacolulan, State of Veracruz, in eastern Mexico. From this mountain, the narrowly endemic species Salvia chazaroana B.L.Turner (Lamiaceae), Lobelia biflora Rzed. (Campanulaceae) and Castilleja eggeri Franc.Gut. & Cházaro were described. Species sharing the habitat are Beschorneria yuccoides K.Koch (Asparagaceae, Agavoideae), Ageratina chazaroana B.L.Turner (Asteraceae, Eupatorieae) and the epiphytic Nelsonianthus tapianus (B.L.Turner) C.Jeffrey (Asteraceae, Senecioneae).

Figure 4. 

Distribution map of the epiphytic species Valeriana rudychazaroi in Mexico.

Miguel Cházaro dedicates the name of the species to Rudy Miguel Cházaro-Hernández, his beloved son, who, since an early age, has accompanied him on numerous botanical trips (Fig. 5). This is the second of a series of new species that Miguel Cházaro wished to dedicate to his children before he died on 4 April 2023. First, the species Eugenia sarahchazaroi Cházaro, Franc.Gut. & J.R.Carral was dedicated to his daughter, Sarah M. Cházaro-Hernández (Francisco-Gutiérrez et al. 2023b). A sketch of the life of Miguel Cházaro can be consulted in his obituary (Francisco-Gutiérrez and Vázquez-García 2023).

Figure 5. 

Author and eponymy of the new species A Miguel Cházaro showing a specimen of Valeriana rudychazaroi next to its host, a Quercus glabrescens tree in Tlacolulan, Veracruz, Mexico (Author: Rodrigo Carral-Domínguez) B Rudy Miguel Cházaro-Hernández, son of Miguel Cházaro, during a botanical expedition at Barranca de Ramírez, 1981 C Miguel Cházaro and his son, to whom he dedicates the name of this new species (Author of B and C: Patricia Hernández-Romero).

The new species has an Area of Occupancy (AOO) of 4 km² and Extent of Occurrence (EOO) of 0 km². A worrying situation for the conservation of this remarkable species is the overexploitation of oak trees that have been felled for charcoal production since the 1930’s decade (Flores 1938). Besides, the cloud forest is the most endangered ecosystem in Mexico, with projections of high vulnerability in the face of climate change scenarios (Ponce-Reyes et al. 2012). That is why, given the reduced values of AOO < 100 km², EOO < 10 km², number of locations = 1 and observed decline in quality of habitat, Valeriana rudychazaroi is classified under the Critically Endangered CR B1+B2ab(ii,v) category.

Valeriana rudychazaroi is the first recorded epiphytic species in the genus. Previous works on worldwide Valeriana species reported habits of small trees, herbs, subshrubs, shrubs or lianas (Weberling and Bittrich 2016). Barrie (2003) reported five species of suffruticose or herbaceous vines in the country, while the checklist of Mexican lianas reported one, V. subincisa (Ibarra-Manríquez et al. 2015). Unlike the Valeriana species that are lianas, this species has short stems that are rooted on the branches of Q. glabrescens trees, flowering and fruiting without contact with the ground. Further studies on seed dispersal and the biology of the species are needed.

Barrie (2003) stated that there are seven species of Valeriana vines in the Americas, four endemic to the northern Andes, one endemic to Panama and Costa Rica and two in Mexico: V. naidae and V. subincisa. Following the dichotomic key provided in Barrie (2003) and considering the habit of this new species, it is closest related to this group, compared to the herbaceous species. Due to the absence of twining stems, the key for species showed the new species to be most similar to V. naidae and V. subincisa, to which it was compared. A detailed comparison is provided in Table 1. The contrasting differences in morphological characters and ecological features allow us to separate V. rudychazaroi from other species that overlap its distribution in western Veracruz in the Cofre de Perote Volcano (Barrie 2003).