Gymnosiphon fonensis Cheek, 2024

Cheek, Martin, Xander M. Van Der Burgt, Tchiengué, Barthélemy, Thiam, Aminata, Molmou, Denise, Doré, Tokpa Seny & Magassouba, Sékou, 2024, New discoveries of plants from Republic of Guinea, W. Africa, including Gymnosiphon fonensis Cheek, sp. nov. (Burmanniaceae), a new Critically Endangered species from Simandou, Adansonia (3) 46 (10), pp. 89-101 : 93-97

Gymnosiphon fonensis Cheek , sp. nov.

( Figs 1-3 ; Table 1 )

Gymnosiphon bekensis sensu Cheek non Letouzey, Kew Bulletin 65: 83 ( Cheek & van der Burgt 2010); Zenodo: 6 ( Gosline et al. 2023) Gymnosiphon fonensis Cheek , sp. nov. resembles G. bekensis Letouzey in the large diameter flowers (10 mm or more diameter), long perianth tube> 10 mm long, absence of long, filamentous, stigma appendages; it differs in that the diameter of the opened corolla (10-11 mm diam.) is exceeded by the length of the corolla tube (13-) 14-18 mm (vs opened corolla 12-15 mm diam. exceeding or equal to the length of the corolla tube (12 mm); stamens inserted at base of distal portion of perianth tube, 4 mm from the mouth (vs inserted at apex of the tube); rhizome lacking scale-leaves (vs with conspicuous scale-leaves).See also Table 1 and the discussion.

TYPUS. — Republic of Guinea • Guinée-Forestière , Simandou Range , Forêt Classée de Pic de Fon , Boyboyba Forest , Oueleba (also known as Ouéléba ) to Wataferedou path; c. 700 m; fl.; 12.IX.2022; Cheek with Molmou 19334 ( holo-, K[K000593362]; iso-, HNG, P) PARATYPI. — Republic of Guinea • Simandou Range, Pic de Fon Forêt Classée , near the northern access road to Oueleba mountain , east of Oueleba 1 camp; 706 m; fl.; 24.VIII2008; Tchiengué 3307 (HNG) • Path from Oueleba 1 to village Wataferedou, north of the path; 740 m alt.; fl., fr.; 31.VIII.2008; van der Burgt 1274 (BR[BR0000019811857], HNG, K[K000460554], MO, P[P06800898], WAG[WAG0115184, WAG0446787]• Ouelaba 1 to Wataferadou path; 750 m; fl., fr.; 18.IX.2008; Cheek 13779 (HNG); Est de Pic de Fon, sud-est de Whisky 1; 864 m; fl.; 18.XI.2008; Traoré A. (= A.S. Goman) 161 (HNG) .

SIGHT RECORDS. — Republic of Guinea • Simandou Range, Pic de Fon Forêt Classée, north of Oueleba, forest beside the road ascending to the ridge; 875 m; fl.; 20.IX.2008; leg. Pierre Haba, Pepe Haba & A. Traoré; Sight Record 101 • Pic de Fon area, west of the pass between villages Moribadou and Lamadou; 970 m; fl.; 25.XI.2008; leg. van der Burgt, Pepe Haba, Pierre Haba, A. Traoré, F. Fofana & B. Diallo; Sight Record 104 • Nionsomoridou, c. 4 km due W of the town, about 100 m due S of the N2 road in gallery forest; 781 m; fl.; 17.IX.2022; Thiam Sight Record (photos).

DISTRIBUTION. — This species is known from the southern half of the Simandou range in the Republic of Guinea, where it is known from five stations ( Fig. 3 ).

HABITAT. — Primary tropical submontane forest 700-970 m altitude. PHENOLOGY. — Flowering was observed from late August to November.

ETYMOLOGY. — The epithet refers to the Forêt Classée de Pic de Fon, comprising the southern half of the Simandou range in the Republic of Guinea, from which the species was discovered and to which the species is strictly endemic on current evidence.

CONSERVATION STATUS. — Despite the fact that all known populations of Gymnosiphon fonensis Cheek , sp. nov. are found in or immediately adjacent to the Forêt Classée de Pic de Fon of the southern Simandou Range, anthropogenic pressure still represents a threat and the range of the species is taken as a single threat-based location in the sense of IUCN (2012). The Pic de Fon location is set to host a major open pit iron ore mine. All sites are on the footprint of the project. While the pit is not expected to directly impact sites for this species, there is a risk that despite best efforts to protect threatened species, there will be negative impacts linked with the activities and infrastructure associated with the expected ore extraction, such as dumping of waste rock, alteration of hydrology and construction of new roads. There has already been a decline in quality of habitat e.g. due to interventions for environmental surveys such as creation of paths (Cheek pers. obs. 2021 and 2022).

DESCRIPTION

Erect, probably perennial, herb 6.5-12(-15) cm tall above roots, above ground part 5-8.3 cm tall, glabrous, achlorophyllous, white when alive. Rhizome pale yellow, vertical, cylindricalellipsoid, 2.5-3 × 1.25-1.5 mm, lacking scale-leaves ( Fig. 2A, B ). Roots 10-17 per rhizome, vermiform, to 3.5 cm long c. 0.2 mm diam., sparingly branched ( Fig. 2A, B ). Tuber(s) absent. Stem (peduncle) terete, erect, single (sometimes the base of the previous season’s peduncle evident adjacent to that of current season’s ( Fig. 2B ).), unbranched or once branched from near the base, c. 0.75 mm in diameter, internodes (2.2-) 5- 7 mm long (underground) or 8-14 mm long (above ground). Scale-leaves sparse, but absent from the base, ovate-oblong 1.1- 1.5 × 0.7-0.8 mm, apex rounded-truncate, base clasping the stem for 40-50% of its circumference, below surface adpressed to the inflorescence axis, above surface spreading by c. 45°. Inflorescence initially single-flowered then cymose-uniparous, 1-3-flowered, flowers developing in sequence. Bracts similar to scale-leaves. Pedicels 0.1-0.5 mm long. Flower white or slightly yellow in bud, white at anthesis, erect, the perianth tube translucent, sometimes curved, otherwise actinomorphic, 15-20 mm long, 10-11 mm wide at anthesis, scent not detected, if present faint (van der Burgt 1274; Cheek pers. obs. September 2022). Perianth tube (13-) 14-18 mm long, cylindrical, 1.7-1.8 mm wide, distal portion of tube (above anther insertion) broadly cylindric, 4 × 2-3 mm. Outer tepals 3, transversely oblong in outline, 4-5 × 4.5-6 mm, patent, with three parallel lobes, equal in length, apices rounded; lateral lobes 1.5-2 mm wide, median 2-3 mm wide. Inner tepals ( Fig. 2E ) alternating with outer, inserted inside perianth tube at (1-) 1.2-1.5 mm below the sinus of the outer lobes, narrowly oblong, erect, 0.8-0.9 × 0.2 mm, apex acute. Anthers ( Fig. 2 G, I ). inserted 3-4 mm below the corolla mouth, at base of the distal portion of the tube, becoming attached to the style head, each 0.5-0.6 mm long, 0.8 mm wide, the two lateral, anther cells orbicular, 0.4 mm wide, immediately adjacent to each other and not separated by the connective, connective absent or inconspicuous. Style cylindrical, 9-10 mm long, 3-lobed at apex, stigmatic head 1.35 mm wide, the three stigmas horizontal to slightly recurved, each obtriangular, 0.7-0.8 mm long, lacking filiform appendages ( Fig. 2 G-I). Ovary cylindric, outer surface lacking conspicuous ribs, 2 × 1.65 mm, unilocular, with 3 protoseptal, intruded parietal placentas, each placenta with 50-60 ovules; septal nectary glands six, each longitudinally ellipsoid c. 0.3 × 0.2 mm., in pairs flanking the protoseptae immediately below the junction with the perianth tube ( Fig. 2J ). Fruit indehiscent, lacking ribs, globose-ellipsoid, 3.7-5.5 × 3-3.5 mm, walls membranous; distal perianth tube remains subcylindrical, tapering gradually towards the apex, c. (1.4-)4-5 × 1-1.2 mm; style exserted 2-4 mm from perianth tube remains. Seeds oblong, 0.25-0.4 × 0.15-0.2 mm, surface reticulate.

Five sites ( Fig. 3 ) are recorded based on eight specimen or photographic records, each site with 2- c. 50 individuals observed. The largest number of individuals, c. 50 was recorded at the type location, a plot of c. 30 m × 10 m within the site of the Boyboyba Forest which itself measures c. 0.4 km 2 in area, while at the northernmost site, only two individuals were recorded. All five sites occur within small patches of submontane forest that appear to be dependent on streams. The forest patches are each far less than 1 km 2 in area, however in calculating the area of occupancy (AOO) we are required to use the IUCN (2012) mandatory grid cell-size of 4 km 2, therefore AOO for Gymnosiphon fonensis Cheek , sp. nov. is calculated as 20 km 2, meeting the threshold for Endangered. However, the actual area occupied by the species is likely to be far less than 1 km 2 and is possibly less than 1 ha. For example, targeted searches at the Boyboyba Forest for achlorophyllous mycotrophs over several days in 2008 and 2022 by specialists (the authors) found Gymnosiphon fonensis Cheek , sp. nov. at only a single plot of c. 30 m × 10 m (see above) while other species of achlorophyllous mycotrophs were found in multiple spots over several hectares within the forest. The sites for Gymnosiphon fonensis Cheek , sp. nov. are globally distributed along a narrow c. 20 km north to south section of the Simandou Ridge. The extent of occurrence is calculated as 44 km 2.

We estimate that less than 100 mature (flowering-sized) individuals are known, qualifies the species as Endangered under Criterion D.

Since there have been past, present and future threats, there is a single threat-based location, and EOO meets the threshold for Critically Endangered under criterion Criterion B, we here assess Gymnosiphon fonensis Cheek , sp. nov. as Critically Endangered, CR B1a,b(iii). It is to be hoped that this species will be searched for and found at other locations which would allow a lower extinction risk assessment than that made here. However, since intensive targeted searches in the correct season in 2008 outside Simandou failed to find this species, the most conspicuous species of West African Gymnosiphon in terms of flower diameter (while more inconspicuous species of the genus were found), it is strange that it has not been detected elsewhere before now, if it indeed has a wider range. However, sites such as Mt Bero where this species might be found have not yet been thoroughly surveyed at the correct season for achlorophyllous mycotrophs.

We recommend that a management plan is developed to ensure the survival of this species and is implemented following the protocols of Couch et al. (2022). This should include a public sensitisation programme, annual monitoring of the Gymnosiphon fonensis Cheek , sp. nov. (and also the Endangered G. samouritoureanus ) populations to determine trends in survivorship and threats, potentially increased guarding of the forest habitat, and seedbanking. Cultivation and translocation of achlorophyllous mycotrophic flowering species such as Gymnosiphon fonensis Cheek , sp. nov. has not yet been achieved but should be possible if sufficient resources and time can be allocated for researching this, for which the first step should be to determine the autotrophic partner species of the fungi upon which the Gymnosiphon depends. Without this information, planning for the translocation of any achlorophyllous mycotroph has a low chance of success.

Figures

FIG. 1. — Gymnosiphon fonensis Cheek, sp. nov.: A, side view of inflorescence, note cylindrical distal portion of perianth tube; B, flower, three-quarter view; C, flower showing outer perianth lobes with equal lateral and median portions; D, Gymnosiphon fonensis Cheek, sp. nov. (left) with Gymnosiphon samoritoureanus (right). A, B, from Cheek 19334, photo M. Cheek; C, D, from van der Burgt 1274, photo X. van der Burgt.

FIG. 2. —Gymnosiphon fonensis Cheek,sp.nov.:A, habit, whole plant;B, habit,base of plant showing:rhizome (dotted) with roots and two stem (peduncle) bases; C, flower and rhachis; D, distal part of open flower; E, corolla tube opened (distal portion) to show inner tepals in relation to style head (with stamens attached) and stigmas; F, lobing of corolla lobes (from one flower); G, stigmatic-style head, with stigmas above, anther cells below, side view; H, as G but dorsal view; I, as G but ventral view (style in transverse section); J, ovary opened with a longitudinal cut, to show the three placental masses with ovules, and (black) pairs of nectar glands; A-I, from Cheek 19334; J, from van der Burgt 1274. All drawn by Andrew Brown.Scale bars: A, 1 cm; B, C, 5 mm; D-F, 5 mm; G-I, 1 mm; J, 2 mm.

FIG. 3. — Gymnosiphon fonensis Cheek,sp.nov.:map of the global distribution. Adapted from Xander van der Burgt,map data Open Street Map.