Passiflora guentheri Harms (1929: 811)

Kuethe, J. R., Balderrama, José A., Fuentes, Alfredo, Justiniano, Hermes & Lanas, Mattias, 2025, Resolving the Passiflora guentheri and P. mapiriensis enigma: identifying a third member of Passiflora sect. Simplicifoliae from the eastern Yungas, Bolivia, Phytotaxa 697 (2), pp. 166-176 : 168-169

Passiflora guentheri Harms (1929: 811) ( figure 1 , 2a–c–e , 4 )

Type:— BOLIVIA. La Paz: Mapiri region, San Carlos, 850 meters, 15 March 1927, fl., O. Buchtien 906 (holotype: B (destroyed). Lectotype: US 00115034, designated here).

Description. Plant a strong tendrillate vine with branches 5–7 m long, glabrous to glaucous throughout, the glaucous vestiture especially potent on younger branches. Stem subterete to very obscurely striate, stark lavender-purple in colour, distinctly glaucous; stipules semi-oblong to rounded or widely reniform, 1.5–2.2 cm long, 0.7–1.2 cm wide, mucronate terminating into a mucro 3–4.5 mm long, becoming slightly yellowish at the tip, margins entire, persistent; petioles 2.5–4.2 cm long, distinctly caniculate, bearing 4–6 opposite to subopposite sessile glands about 0.8–1.0 mm in diameter, glands raised, consistently having 2 opposite glands located just below the blade. Leaves ovate to ovate-lanceolate, 7.5–15 × 3.2–7.5 cm wide, gradually acute towards the apex, shallowly cordate at base, margins entire throughout, quintuple-veined with conspicuously reticulate veins, foliar texture thick coriaceous, persistently conduplicate folded, bright green above, glaucescent beneath. Inflorescence singular, with purple to lavender flowers; peduncles stout, 3–4.5 cm long, borne sub horizontally; bracts ovate-lanceolate, often deciduous, 6–7 mm long, 2–3 mm wide, acuminate at apex, cordulate, borne about 15–18 mm below the base of the flower. Flower showy, 8.5–10 cm in diameter, lavender with purple, sepals and petals slightly reflexed at anthesis, scented; hypanthium broadly campanulate, about 6–7 mm long, green and glaucous externally, white internally; sepals linear-oblong, 4.1–4.8 cm long, 1.2–1.5 cm wide, obtuse and slightly cucullate at apex, dorsally corniculate, awn a distinctly hooked, 3–4 mm long keel, lavender blue adaxially, a light green abaxially; petals linear-oblong, slightly shorter than sepals, 3.6–3.9 cm long, 1.0– 1.2 cm wide, obtuse, very membranous, lavender-purple; corona in 5–6 series, purple of various shades of intensity; outer series liguliform, 2.8–3.4 cm long, wine red at base becoming purple-blue towards the apex terminating in a whitish tip, a single slightly paler band around 1/3 the length, slightly wavy in upper part; inner 2–3 series stubby, 1–2 mm long, dark wine-red; innermost 2 series capitellate, erect, increasing in size to 3 and 5 mm respectively, wine-red leading to a white to whitish tip; operculum complex, 8–11 mm high, connate and cleft nearly to base of the androgynophore into slightly overlapping segments giving the base a somewhat plicate appearance, upper portion becoming distinctly filamentose, wine red in basal half, white to light pink in upper half; limen closely surrounding base of gynophore, membranous; androgynophore greenish-brown with purple speckles, about 11–15 mm tall; ovary ovoid, glaucous; pollen orange-yellow; anthers greenish-yellow; stigma deep green throughout. Fruit [immature] globose to subglobose, greenish blue with glaucous covering.

Distribution, habitat and conservation. Out of the two species collected by Otto Buchtien, Passiflora guentheri is noticeable the more common across Bolivia. The authors have sighted five new populations for the species, including regions such as Apolo, Mapiri, Caranavi and Villa Tunari where it grows in sub-Amazonian premontane forests at elevations between 800 and 1350 m. Two more populations were identified from nameless herbaria at Santa Cruz (USZ) and La Paz (LPB), Wood et al. 19897 and Landivar et al. 16, adding to a total extent of occurrence (EOO) of 9,200 km 2 and an area of occupancy (AOO) of 40 km 2. This would class Passiflora guentheri as Vulnerable to Endangered in accordance with the IUCN (2022) guidelines.

Plants were seen growing almost exclusively in the direct vicinity of water, whether it being next to a small river or in the wake of a waterfall. This strongly suggests that the species requires high levels of moisture year-round, but also poses a possible conservation risk as contamination upstream could mean adversity to plants growing alongside the river downstream. Mining is a significant conservation concern throughout the regions where Passiflora guentheri was found, alluding to further deterioration of habitats and rivers in the nearby future. For this reason, the authors agree EN (endangered) may be an adequate assessment for this species.

Notes. Killip (1938) and Harms (1929) were correct keeping it as two separate species, for their differences extend both vegetative and floral morphology. The original opercular traits that Killip described for Passiflora guentheri are less unique than what he made out in his writings ( Killip 1938). The virtually plicate structure is shared similarly with other species from this alliance (i.e. P loretensis Killip (1931: 349) , and P. populifolia Triana & Planch. (1873: 150)) , including P. mapiriensis albeit lesser distinct. A new trait that showed to be rather consistent among the several populations sighted, however, were the remarkable purple stems which, against the fresh green foliage, marked a stunning contrast in colour and a ready means of identification for the species. The leaves are distinctly coriaceous in texture, and noticeable folded in a “V” shape (conduplicate) orientation throughout.

Other differences include vestiture and vegetative texture, with Passiflora guentheri being distinctly glaucous with thick coriaceous laminas, while in P. mapiriensis the vestiture is sparingly pubescent to puberulent, and the leaves noticeably more membranous in texture. The distribution appears to be scattered, and although P. mapiriensis was explicitly named after the Mapiri region, we only found P. guentheri plenty within this region. Lastly, in regard to its taxonomic placement within the genus, despite the dissitate bracts, something seen also in P. populifolia and P. herthae Harms (1940: 49) , the flower is consistent with the members of sect. Simplicifoliae and thus should be placed accordingly.

Figures

FIGURE 1. Botanical illustration showing Passiflora mapiriensis (A-F) and P. guentheri (G-L) in detail. Drawn from photographs taken in the field. P. mapiriensis: A) habit; B) petiolar nectaries; C) leaf outline; D) stipules and developing buds; E) bract; F) flower. P. guentheri: G) habit; H) petiolar nectaries; I) leaf outline; J) stipules; K) bract; L) flower. Drawn by Mattias Lanas.

FIGURE 2. Comparative rubric between P. guentheri (A,C,E) and P. mapiriensis (B,D,F). Note their subtle botanic differences including the shape and size of the stipules, floral structure, vegetative indument and foliar orientation. The stems and abaxial side of the leaves in P. mapiriensis are minutely pubescent (F), whereas in P. guentheri the stems and vegetative parts are glaucous (E). The number of petiolar nectaries or their respective location along the petiole is variable. Made with photographs taken by J.R. Kuethe (ACDEF) and Jose Balderrama (B). All photographs taken in situ.

FIGURE 4. Distribution map showing the three members of sect. Simplicifoliae distributed across Bolivia. Passiflora guentheri (green squares); Passiflora mapiriensis (blue triangles); Passiflora chaskajina (red circles). Shaded areas given for their possible distribution extents.