Rafflesia banaoana (Malabrigo, Asia Life Sciences 4:139–146) A.B.Tobias, Thorogood & Malabrigo 2023

Tobias, Adriane B., Thorogood, Chris J. & Malabrigo Jr, Pastor L., 2023, The reinstatement of Rafflesia banaoana (Rafflesiaceae), and implications for assessing species diversity and conservation requirements of the world's largest flowers, Phytotaxa 612 (2), pp. 201-216 : 205-207

1. Rafflesia banaoana (Malabrigo, Asia Life Sciences 4:139–146) A.B.Tobias, Thorogood & Malabrigo stat. nov.

Figs. 2‒3

urn:lsid:ipni.org:names:60478521–2

Type: — PHILIPPINES. Luzon Island, Kalinga Province, Balbalan Municipality, Barangay Balbalasang, Sitio Cafcafulao, Banao Protected Landscape, 1361 m elev., 04 May 2009, Malabrigo 605 (holotype: LBC!)

Description:— Endophytic holoparasite (devoid of leaves). Mature bud 16–18 cm diameter, pale yellowish-pink. Cupule c. 2.5 cm high, 9 cm wide. Bracts dark brown to black, in a set of 5 imbricate whorls, 5 bracts per layer, outermost smallest, c. 1.5 cm by 2.5 cm, innermost largest, c. 7.5 cm by 12 cm. Flowers (20–)30–47(–50) cm diameter when fully expanded, 10–15 cm high. Perigone tube slanted, 5–7 cm long. Perigone lobes 5, 10–15 cm by 10–16(– 20) cm, 7–11 mm thick, reddish-orange in color becoming darker with age, apex slightly recurved, broadly orbicular, basally widely separated (non-overlapping), with margins entire to irregularly repand, covered with conspicuous, large, round and elongated, embossed warts, smaller ones interspersed, white in color becoming concolorous with background with age. Diaphragm 18–22 cm diameter, 2–2.5 cm wide from aperture rim to base of perigone lobe, 6 mm thick at base, background concolorous with perigone, outer surface with shallow indentations, small ivory warts regularly scattered around the aperture rim, larger ones appearing elevated due to indentations, mainly near the base of the perigone. Diaphragm Aperture 16–20 cm diameter, rim maroon gradually becoming white towards the margin. Windows absent. Ramenta reddish orange, up to 2.5 mm, sub-filiform to tuberculate, with few lobed ramenta in the lower perigone tube, shallowly and deeply-bilobed and multi-lobed with few merged ramenta in the middle perigone tube, multi-lobed, merged and fence-like ramenta in the upper perigone tube and near the diaphragm’s aperture. Disk 8–9 cm diameter, 1.5–1.6 cm thick, reddish-orange becoming darker with age, centrally dome-shaped, rim extended horizontally, margin darker in color, hispidulous, upper surface smooth, shiny, and leathery, with conspicuous processes about 0.5–1.5 cm in height and rudimentary processes of <1 mm height, under surface of male flower reddish-orange, with bristles about 1–3 mm long; female flower white in the middle part with minute brown dots, reddish-orange near the margin. Processes (13)19–26, concolorous with disk, apex hispidulous, those of the female flower generally shorter, conical, and pointed outwards; those of the male flower longer, conical, flattened apically. Male flower generally larger in size, without vestigial ovary, anthers 18–22, 2–2.5 mm diameter, globose attached on brown structure about 5 mm wide, immersed in anther sulci 6–7.5 mm long and 4.5–7 mm wide; neck of the column 0.8–1.0 cm height, 4 cm diameter; lamella 20, 5 mm long from the neck margin, lacuna (or grooves between the lamella on annulus interior) 3–7 mm long and 4–4.5 mm wide, hispid; interior annulus structure smaller than the disk, 6.5–7 cm diameter, reddish-orange becoming darker towards the margin; exterior annulus structure 1–2 cm from the edge of the interior annulus structure, concolorous with the disk’s upper surface, glabrous, forming a hump-like structure that separates the ramenta on the perigone tube. Female flower smaller in size, with vestigial grey anthers in narrow grooves of disk’s undersurface; neck of the column 6–8 mm height, 4 cm diameter, margin lobed; interior annulus structure smaller than the disk, 7–7.5 cm in diameter, orange in color, surface glabrous but hispidulous along the margin, and with bristles in the grooves, grooves expanded at the neck, 6–8 mm long, 2–3 mm wide; exterior annulus structure similar with the male flower, ovary 4 cm wide, 1.5 cm height, lunate-triangular, acutely angled. Fruit and seeds not observed.

Distribution and habitat: — Rafflesia banaoana is endemic to Luzon Island, in tropical montane forests of Cordillera Central ( Figs. 4a‒d ). It grows on steep slopes near river at 1100–1400 m elev. It parasitizes Tetrastigma cf. sepulchrei Merr. (1912:88) and T. loheri ( Gagnep 1910:210) .

Phenology: — Rafflesia banaoana has been observed flowering between March to June, with an apparent peak in May. Fruiting has not been observed but probably occurs from October to December.

Provisional conservation status: — Critically Endangered B1b(iii,v)+C2b. The species is previously known only from its type locality in Sitio Cafcafulao (=Mt. Cabcabulao). Additional localities were identified on Mt. Magadgad at 1370 m elev. and Mt. Ab-abaka at 1140 m elev. in Barangay Balbalasang, Municipality of Balbalan (See Fig. 1 ). It has also been recorded in Kulaju Forest in Barangay Basao, Municipality of Tinglayan at 1200 m elev. The estimated EOO of R. banaoana is estimated at 80 km 2 therefore within the threshold of threatened category. The number of individuals of R. banaoana in all localities is estimated to be fewer than 250 and is documented to fluctuate markedly. Agricultural land expansion, increased frequency of forest fires, and human disturbance serve as the main threats to the natural habitat of the species.

Additional specimens examined: — PHILIPPINES: LUZON, Kalinga Province, Banao Protected Landscape, Balbalan Municipality, Mt. Magadgad, 1370 m elev., 09 May 2019: Tobias 2019–1, male flower ( LBC!); Tobias 2019–2, female flower ( PNH!), Tobias 2019–3, flower bud ( PUH!); Barangay Balbalasang, 02 June 2015: LBC No. 9581, male flower ( LBC!).

Figures

FIGURE 1. Distribution map of Rafflesia banaoana and R. leonardi.

FIGURE 2. Rafflesia banaoana. A. Female flower. B. Cross section showing the processes, annulus structure and ovary. C. Annulus interior of female flower. D. Disk undersurface of male flower. E. Processes. F. Ramenta near the base of perigone tube. Drawn from Tobias 2019-1 (LBC) and Tobias 2019-2 (PNH) by C.J.Thorogood

FIGURE 3. Rafflesia banaoana. A1. Dissected male flower bud. A2. Flower bud. B. Lateral view of the perigone lobes with bracts. B. Female flower. d1. Enlarged view of the surface of perigone lobes with warts. d2. Enlarged view of the diaphragm’s surface. E1. Dissected perigone tube showing filiform ramenta. E2. Simple filiform with few lobed ramenta in the lower perigone tube. E3. Shallowly and deeply-bilobed and multi-lobed with few merged ramenta in the middle perigone tube. E4. Multi-lobed, merged and fence-like ramenta in the upper perigone tube and near the diaphragm’s aperture. F. Dissected female flower showing the characters of the processes, disk, column, annulus structure and ovary. G1. Annulus structure of male flower.’ G2. Disk under surface showing anthers embedded in sulci. G3. Annulus structure of female flower. G4. Stigmatic surface. H1. Column of male flower showing conspicuous processes pointed towards the margin of the disk. H2. Top view of the processes. H3 and H4. Processes of female flower with apical hairs. H5. Enlarged view of the column showing short hairs on disk’s rim and bristles on the disk’s undersurface and annulus interior. and I. Tetrastigma cf. sepulchrei, host of R. banaoana. Photo credits:A1, A2, B, C, E1, E2, E3, E4, F, G3, G4, I—A.B. Tobias. D1, D2, G1, G2, H1-H4—G.K. Penetrante

FIGURE 4. Habitat of Rafflesia banaoana and R. leonardi. A. Overlooking view of mountains in Banao Protected Landscape (BPL). B. Mature flower of R. banaoana (~43 cm across) in Mt. Magadgad. C. Habitat of R. banaoana in Mt. Mapga. D. R. banaoana with the park rangers of BPL. E. Habitat of R. leonardi in Calabgan Watershed Forest Reserve (CWFR) with the locals and staff of the protected area. F. Flower buds of R. leonardi in CWFR. G. Habitat of R. leonardi in Amro River Protected Landscape. H. Vegetation in the type locality of R. leonardi in Mt. Rabuaran, Sitio Kanapawan, Barangay Bolos Point.—Photos by A.B.Tobias