Marijordaania filiformis (Davison) A.E.van Wyk & R.G.C.Boon, 2024

van Wyk, Abraham E. & Boon, Richard G. C., 2024, Marijordaania (Celastraceae: Cassinoideae), a new monotypic genus from South Africa, Plant Ecology and Evolution 157 (1), pp. 100-112 : 100

Marijordaania filiformis (Davison) A.E.van Wyk & R.G.C.Boon comb. nov.

Figs 1 , 2 , 3

Gymnosporia filiformis Davison, Bothalia 2: 311. 1927. ( Davison 1927).

Maytenus " Maytenus sp." ( Pooley 1993: 264).

Maytenus " Maytenus sp. A" sensu Van Wyk (1984) non Schmidt et al. (2002) ( Coates Palgrave 2002: 596; Boon 2010: 308).

Illustrations.

Abbott (1985: 11, Gymnosporia filiformis Davison p.p., top plate); Pooley (1993: 265, Maytenus sp., two photographs in top row); Boon (2010: 309, Maytenus sp. A, three photographs in bottom row); Van Wyk et al. (2011: 447, Maytenus sp. A).

Type.

SOUTH AFRICA • Natal [KwaZulu-Natal], Inanda [2830DB]; recd. Jan. 1880 (K), Dec. 1881 (BOL); Wood 734; lectotype (designated here): K [K000035898]; isolectotypes: K [K000035899], BOL, PRE [PRE0259491-0] .

Description.

Evergreen, slender, lax, semi-scandent, sometimes ascending, shrub or rarely a small tree up to 6(-8) m tall, unarmed, glabrous, leaves and bark lack elastic threads on breaking; new growth reddish, reddish brown, or bronze. Trunk usually multi-stemmed from ground level, up to ca 10 stems, usually fewer, possibly producing suckers from subterranean roots, individual stems up to ca 40 mm diam. near ground level. Bark smooth, grey-brown, much-covered in crustose lichen. Branches slender, flexuose, initially reddish brown, soon changing to green, 4-lined due to 2 narrow wings extending down the stem from the leaf base, with pale, moderately dense lenticels when young, finally terete, grey, lenticels obscure. Stipules marcescent, free, paired, lateral, lanceolate, 0.4-0.5 mm long. Leaves simple, alternate, distichous, ovate or elliptic, (15-)40-65(-92) × (10-)20-35(-45) mm; base rounded; apex acute to narrowly acute or acuminate, rarely obtuse, mucronulate, gland-tipped; margin flat, glandular-denticulate to glandular-serrulate mainly in the distal half to two-thirds, with up to 18 irregularly- and well-spaced, dark teeth on each margin, usually fewer; chartaceous to thinly coriaceous; mature leaves dark green above, some leaves with ca circular patches of crustose, grey lichen, paler green below; midrib on adaxial surface prominent, raised and angled, raised in the proximal half of the abaxial surface and rounded, becoming plane in the distal half, brochidodromous; secondary (principal lateral) veins ca 6-10 pairs, raised on adaxial surface, obscure on abaxial surface; tertiary veins coarsely reticulate, distinct on adaxial surface, indistinct below. Petiole ca 1.5-2 mm long, canaliculate above, decurrent, forming raised lines on branchlets. Inflorescences cymose, solitary, axillary, 1- or 2(3)-flowered, peduncle 2-5 mm long, tipped by persistent lanceolate bracts 1-2 mm long, ca 1 mm wide. Flowers bisexual, actinomorphic, pentamerous, ca 10 mm in diam.; pedicel filiform, pendant, (20-)35-40(-45) mm long, articulated ca 0.5 mm above the base, reddish green. Sepals free, unequal with 2 smaller outer ones, 3 larger inner ones, green, pinkish green to pink-red with margin entire, whitish, the outer ones ca sub-orbicular, ca 1 × 1.5 mm; margin entire; apex rounded and shortly mucronate, the inner ones sub-orbicular, ca 1.5 × 2.5 mm, apex rounded or obtuse, shortly mucronate. Petals sub-orbicular, ca 4.5-5 × 3.5 mm; base cuneate; apex rounded; margin undulate, entire, central part pink-red, fading distally into a white margin. Stamens with filaments arising from the centre of the disc lobes, erect, ca straight, terete, gradually widening to the base, ca 0.5 mm long; anthers dorsifixed, directed upwards, dehiscing by longitudinal slits; pollen pale yellow. Disc prominent, ca 3 mm in diam., comprising 5 discoid subunits, each ca 1 mm in diam., fleshy, green to pale yellowish green or yellowish. Ovary almost entirely included in and adnate to the disc, 5-locular with 2 erect collateral ovules in each locule; style ca 0.5 mm long; stigma capitate. Fruit capsular, 1-5-locular, flattened globose and lobed, ca globose when 1-locular, dehiscing loculicidally to the base, ca 8-12 × 15-17 mm in dry specimens, tipped by the persistent style and stigma, smooth, light yellowish green, calyx persistent, sepals revolute. Seed red-brown, 7-8 × 5 mm; aril white enveloping more than half the seed, margin irregularly lobed, smooth-surfaced but sparsely puberulent towards the base.

Distribution.

Floristically, the range of Marijordaania filiformis (Fig. 3 ) falls within the Maputaland-Pondoland Region ( Van Wyk and Smith 2001), which is more or less congruent with the Maputaland-Pondoland-Albany Hotspot, one of 36 global biodiversity hotspots ( Steenkamp et al. 2004). According to confirmed (vouchered) records, it occurs from Ongoye Forest Nature Reserve in KwaZulu-Natal in the north to Dwesa-Cwebe Nature Reserve at the mouth of the Mbashe River in the Eastern Cape in the south. Within this range, the species is known from ca 12 disjunct localities.

Additionally, there are four other possible or probable localities for the species (Fig. 3 ). The northernmost two are on privately-owned farms about 20 km apart in the Lebombo or Lubombo Mountains of Eswatini (formerly Swaziland), where they were photographed, and material was collected around 2004 (Linda Loffler pers. comm. 10 Aug. 2022). The southern one of these localities is about 265 km north of Ongoye Forest Nature Reserve in KwaZulu-Natal, South Africa. Unfortunately, the herbarium specimen has been lost, but a plant was collected and cultivated. It still survives in a garden in Mbabane, Eswatini (Linda Loffler pers. comm. 10 Aug. 2022). However, the presence of the species in Eswatini still needs confirmation since there is no herbarium voucher specimen available.

The third potential locality for the species is the Ozwatini Plateau north of Ndwedwe in central KwaZulu-Natal, South Africa. A specimen from here (Scott-Shaw 2057 in CPF, now incorporated in NU) might be M. filiformis , but the flowers are too young to be certain. The fourth possible locality is the Majuleni Forest located along a small tributary of the Mtentu River near Baleni, Pondoland, Eastern Cape, South Africa. This locality is almost certainly correct, but it is based on a photographic record with no voucher specimen having been preserved (Dorothy McIntyre pers. comm. 4 Mar. 2019; Sinegugu Zukulu pers. comm. 28 Jul. 2023).

Habitat and ecology.

Marijordaania filiformis occurs in the understorey of sub-tropical Scarp Forest (vegetation type FOz5 of Mucina and Rutherford 2006; SANBI 2006-2018), where it grows in deep shade near watercourses and rocky places, such as at the base of cliffs. It is found from near sea level at southern localities (probably above 50-100 m, but exact collecting information is unknown) to elevations of about 470 m in the north.

The geology of the parent rock where the species is found can be igneous, metamorphic or sedimentary ( Johnson et al. 2006). South of Port St Johns in the Eastern Cape, it is associated with sedimentary rock of the Karoo Supergroup, further north in Pondoland with Msikaba Formation sandstone, at Durban it is associated with Natal Group sandstone, and at Ongoye Forest Nature Reserve, it is associated with granite-gneiss of the Ongoye Complex. If it occurs in the Lubombo or Lebombo Mountains of Eswatini, it will likely be associated with rhyolitic lavas of the Jozini Formation.

Essentially, very little is known about animals associated with M. filiformis . Whitefly pupae of the family Aleyrodidae were found on the leaf undersides at the Krantzkloof Nature Reserve, Durban. It is noteworthy that similar whitefly pupae were observed in a photograph, most likely of our species, in the Majuleni Forest, Pondoland.

Phenology.

Fertile material is infrequently encountered and, when present, there are usually few flowers and fruit. Flowering and fruiting are apparently not linked to seasons as fertile material has been collected in most months of the year.

Vernacular names.

English vernacular names in use are "red-flowered false silkybark" and "red-flowered silkybark", and Afrikaans names are “rooiblomvalssybas” and “rooiblomsybas” ( Boon 2010; Van Wyk et al. 2011). The first mentioned of these English and Afrikaans names are the ones recommended by the Dendrological Society of South Africa ( Von Dürckheim et al. 2014). No names have been recorded in any of the other local languages.

Preliminary IUCN conservation assessment.

Endangered: (EN) C2a(i). The EOO of M. filiformis was estimated at 6865 km2. The AOO calculated was 56 km2 using the recommended 2 km cell width. The areas were determined using the localities where the species has been collected. Only one herbarium collection included geographic coordinates, therefore the localities used in the assessment are not precise. A 2 km cell width seems reasonable given that the species occurs in relatively small, discrete forest patches surrounded by unsuitable habitat. A 2 km cell drawn around the estimated localities includes most of the forest at that location.

Marijordaania filiformis occurs in 15 subpopulations as defined by the IUCN (2012). There are no estimates of the population or subpopulation sizes. In our experience, the species occurs only in small numbers where it is found. It seems unlikely that there are more than 100 mature individuals in any subpopulation, which means the overall population size is probably fewer than 1500. Some subpopulations may be too small to be viable in the long-term.

Most subpopulations are separated from the nearest subpopulation by large distances and unsuitable habitat, thus genetic or demographic exchange seems unlikely. In three cases, two subpopulations are about 6 km apart and there are forest links in between. In these instances, it could alternatively have been assumed that plants at the two localities belong to a single larger population. However, M. filiformis has specific habitat requirements, is rare within suitable habitat, and produces few flowers and fruits, which means that subpopulations separated by even fairly small distances are probably functionally disconnected.

Several of the subpopulations are protected in statutory conservation areas. Subpopulations that are inadequately protected are threatened by degradation of their forest habitat. Marijordaania filiformis is not known to be used for traditional purposes. The species occupies rocky habitats, which affords it protection from wildfire. Individuals that grow adjacent to rivers are probably at risk of being killed or damaged by floods. Both wildfire and flooding are likely to increase across the species’ range due to climate change. The species probably reproduces mainly clonally, which means that genets in the sub-populations are genetically identical.

There is no evidence for a large reduction in population size, which is required for threatened Category A. The EOO and AOO distribution thresholds of Vulnerable and Endangered respectively are met for Category B, but only one of the three conditions is met (B2(b)), therefore the taxon does not qualify in this category. It is possible, perhaps even likely, that the estimate of 1500 mature individuals is too high and the species qualifies for Vulnerable in Category D1, but unfortunately there is no evidence to support this, and there are insufficient data to do the quantitative analysis required to qualify for Category E.

While the size and rate are unknown, the species’ population size is inferred to be declining due to apparent ongoing infrequent recruitment and establishment of new plants, and habitat degradation at some localities. With an estimated population size of <2500 individuals and <250 mature individuals in each sub-population, the species should be classified as Endangered (EN) C2a(i). There is a need to survey the subpopulations more fully to get a better understanding of threats and population size and trends.

Additional material examined.

SOUTH AFRICA - KwaZulu-Natal • Zululand, Ngoye [Ongoye Forest Nature Reserve], [2831DC]; 18 Aug. 1985; Abbott 2682; PCE, PRU • Mtunzini District , left hand branch of Ngoya Forest Road [Ongoye Forest Nature Reserve], [2831DC]; 20 Feb. 1961; Wells & Edwards 95; NU, PRE • Krantzkloof Nature Reserve , (2930DD); 12 Jul. 2014; Boon 69; NH • Krantzkloof Nature Reserve , (2930DD); 29 Jan. 1984; Jordaan 304; NH • Kloof Nature Reserve [Krantzkloof Nature Reserve], Pinetown District , [2930DD]; 16 Feb. 1966; Moll 3021; NU, PRE • Durban, Krantzkloof Nature Reserve , (2930DD); 20 Jan. 1988; Van Wyk 8243; PRU • Krantzkloof Nature Reserve , north of Kloof Falls Road , (2930DD); 20 Jan. 1988; Williams 158; NH • Ntimbankulu [Ntimbankulu Nature Reserve], (3030CB); 21 Jun. 1984; Abbott 2002; PCE, PRU • Oribi Gorge [Oribi Gorge Nature Reserve], [3030CB]; Sep. 1996; Edwards 1438; NU • Umtamvuna Nature Reserve , Smedmore Forest , (3130AA) [3030CC]; 22 Feb. 1986; Abbott 3018; NH, NU, PRU • Umtamvuna Nature Reserve , Smedmore Forest , (3030CC); 27 Jul. 1986; Abbott 3217; PRU • Umtamvuna Nature Reserve , Smedmore Forest , (3030CC); 23 Apr. 1989; Abbott 4366; PRU • Umtamvuna Nature Reserve , Smedmore Forest , (3030CC); 11 May 1992; Abbott 5768; PRU • Umtamvuna Nature Reserve , Smedmore Forest , (3030CC); 9 Jul. 2008; Abbott 8901; PRU • Umtamvuna-natuurrreservaat [Umtamvuna Nature Reserve], Smedmore-woud [Smedmore Forest], (3030CC); 10 Jun. 1982; Abbott s.n.; PRU • Umtamvuna Nature Reserve , Smedmore Forest , (3030CC); 14 Jul. 1983; Jordaan 264; NH • Smedmore [Smedmore Forest, Umtamvuna Nature Reserve], [3030CC]; 10 Jun. 1982; Nicholson 2259; NU, PRE • Umtamvuna Nature Reserve , Smedmore Forest , (3030CC); 4 Sep. 1994; Van Wyk BSA 2576; PRU • Umtamvuna Nature Reserve , Smedmore Forest , (3030CC); 15 Oct. 1984; Van Wyk & Lowrey 6826; PRU • Umtamvuna Nature Reserve , Smedmore [Smedmore Forest], (3030CC); 15 Oct. 1984; Van Wyk & Lowrey 6827; PRU • Umtamvuna Nature Reserve , Smedmore [Smedmore Forest], (3030CC); 15 Oct. 1984; Van Wyk & Lowrey 6831; PRU • Umtamvuna Gorge, Umtamvuna Valley bottom, [3130AA]; 10 Nov. 1994; Meter 100; NU . - Eastern Cape • Mbotyi, Ntsubane Forest, (3129BC); 21 Aug. 1989; Abbott 4416; PRU • Mkambati Nature Reserve , Daza Riverine Forest , (3129BD); 11 Nov. 1984; Jordaan 329; NH • Mkambati Nature Reserve , (3129BD); 11 Dec. 1986; Jordaan 1016; NH • Lwandile north of Umtata River mouth, Nkwintyini Forest , (3129CC/DD) [3129CC]; 7 Apr. 1990; Cooper 253; NH, PRE • Upper Bulawa Forest near Mpande, (3129CD); Cooper 262; NH • Port St Johns , Mount Sullivan , (3129BC) [3129DA]; 2 Oct. 1988; Abbott 4153; PCE, PRU • Mount Sullivan , Nenga Forest , (3129DA); 11 Jan. 1989; Abbott 4206; PCE, PRU • Port St. Johns , Silaka Nature Reserve , (3129DA); 4 Aug. 1988; Van Wyk 8407; PRU • Port St. Johns , Mtambala Forest Station , (3129DA); 5 Aug. 1988; Van Wyk 8429; PRU • The Haven [The Haven Hotel], Elliotdale District , [3228BB]; 13 Feb. 1967; Gordon-Gray 1347; NU • Transkei, Dwesa Nature Reserve , S. of Mendu River Mouth , (3228BD); 1 Aug. 1988; Van Wyk 8334; PRU .

Notes.

In nature, sterile, fresh material of Marijordaania filiformis can potentially be confused primarily with Maytenus cordata (Fig. 4 ). The previous association of the former with Maytenus acuminata and Maytenus abbottii was not because of morphological similarities, but due to the broad species concept adopted for Maytenus acuminata by Marais (1960). Selected morphological features to distinguish among Marijordaania filiformis , Maytenus acuminata , Maytenus cordata , and Maytenus abbottii are provided in Table 1 .

A particularly reliable field character for the identification of some southern African members of the Celastraceae is to test for the presence of elastic (rubbery) threads associated with the phloem tissue of, among others, the leaf venation and bark ( Van Wyk and Van Wyk 2019). These threads are composed of gutta-percha (trans-1,4-polyisoprene) and are found in several members of the Celastraceae (e.g. Drennan et al. 1987; Simmons 2004). For this test, crease a fresh leaf blade transversely and slowly, very gently pull it apart along the crease for about 2 mm. If gutta-percha is present, silvery elastic threads will connect the two halves of the blade (Fig. 4B ). Elastic threads are absent in Marijordaania filiformis , but are always present in Maytenus cordata , Maytenus acuminata , and Maytenus abbottii .

The long, pendant, filiform pedicels of Marijordaania filiformis are usually 35-40 mm long, whereas in the other species they are mostly shorter than 10 mm during flowering. The pedicels may elongate when in fruit, but never match the length of those in M. filiformis . Marijordaania filiformis has pink-red petals with white margins (Fig. 2A-E ), as opposed to pale green petals in Maytenus cordata (Fig. 4A, C ), white or cream petals in Maytenus abbottii (occasionally with a pale pink tinge), and cream or white petals which may exhibit pink tinges in Maytenus acuminata . In Maytenus cordata and Maytenus acuminata , the filaments are flattened and inserted under the margin of the disc. In Maytenus abbottii , the filaments are flattened and united at the base, forming a short, cup-shaped staminal tube. Additionally, the filaments are incurved apically and the anthers are directed downwards. In M. filiformis , the filaments are straight, terete, and inserted into the centre of the discoid lobes (Figs 1C, F , 2C, D ), with the anthers directed upwards. In M. filiformis , the aril is white (Fig. 2G ), puberulent at the base only, and encloses most of the seed. Maytenus abbottii has a white, puberulent aril, which envelopes only the basal portion of the seed with long, free lobes that exceed the length of the seed. The aril in Maytenus acuminata and Maytenus cordata is orange and completely surrounds the seed (Fig. 4B ).

Additional differences include Maytenus abbottii having tetramerous flowers, while the other species have pentamerous flowers. Maytenus acuminata reaches tree proportions and often grows in exposed positions such as forest margins and around rock outcrops. On the other hand, the other species are slender shrubs to small trees, predominantly occupying forest interior habitats, often in deep shade. Maytenus cordata is a more erect plant with glossier leaves, and its new growth is green, in contrast to the bronze to reddish green new growth observed in M. filiformis .

Unlike the situation in nature, dried material of Marijordaania filiformis can easily be confused with that of Maytenus cordata in herbaria, especially those forms of the latter with shortly petiolate leaves and a rounded or cuneate lamina base. Unfortunately, testing for elastic threads in herbarium material is unreliable, and especially in older material the threads may no longer be detectable. As explained earlier, Davison (1927) confused these two species, despite the herbarium material being in flower. One of us (AEvW) has also erroneously cited as a voucher for Marijordaania filiformis p.p. a specimen of Maytenus cordata (Wood 11608 in NH) ( Van Wyk 1984). Probably the most reliable character in the case of herbarium specimens with flowers is to dissect an ovary and confirm the number of locules; five in Marijordaania filiformis , three in Maytenus cordata .

In herbaria, Marijordaania filiformis can, in addition to the difference in the number of locules, also be distinguished from Maytenus cordata by its flowers being larger, ca 10 mm in diam. [vs smaller, ca 6 mm], cymes 1- or 2(3)-flowered [vs more floriferous, usually 6-8-flowered, these opening successively over time], pedicels (20-)35-40(-45) mm long, pendant [vs 4-10(-20) mm, erect or spreading], and articulated ca 0.5 mm above the base [vs (1.5) 2.0-4.0(-8) mm]. The part of the pedicel below the articulation is persistent, hence providing a useful taxonomic character for distinguishing between the two species, especially in herbarium specimens of which the open flowers have already been shed.

Figures

Figure 1. Marijordaania filiformis. A. Flowering branchlet. B. Inflorescence, showing short peduncle with bracts and a single flower in bud (just before anthesis). C. Flower, viewed from above. D. Flower, viewed from below. E. Transverse section of ovary, showing five locules, each with two ovules. F. Single stamen, inserted on swollen, discoid, lobe of disc. G. Selection of almost mature, intact fruit, plus one old, dehisced and empty one; shape varies depending on the number of ovules that develops into seed. H. Seeds, three with the aril intact, one with aril removed. Scale bars: A, G = 20 mm; B-D, H = 5 mm; E, F = 1 mm. A based on Jordaan 394 (NH), B-F from Abbott 1798 (PRU; spirit collection), and G-H from Abbott 6082 (PRU; spirit collection). Drawn by Daleen Roodt.

Figure 2. Marijordaania filiformis. A. Flowering branchlet, viewed from below; note distichous arrangement of leaves. B. Branchlet showing flowers borne on long, slender, and pendant pedicels; also present is a young developing fruit. C. Flowers; note each stamen inserted on a swollen discoid subunit of the disc. D. Flower viewed obliquely from the side. E. Flower, viewed from below. F. Fruit, intact and almost mature. G. Fruit, dehisced, showing a dark-coloured seed partly covered by a white aril. Photographs A-C by Sharon Louw; D-G by Richard Boon.

Figure 3. Topographical map showing the known distribution of Marijordaania filiformis. Solid circles indicate localities supported by herbarium specimens; open circles with small central dots depict sight and other records in need of vouchers (details in text). The insert shows a map of southern Africa with names of countries; the grey rectangle indicates the area depicted by the topographical map.

Figure 4. Maytenus cordata. A. Flowering branchlet; note cordate leaf bases and flowers with relatively short pedicels. B. Branchlet with mature, dehisced fruit, showing seed with orange-yellow aril; insert shows a dehisced capsule with seeds completely enclosed by an orange aril. Upper right hand leaf blade broken in half and gently pulled apart to show the presence of silvery elastic threads of gutta-percha. C. Inflorescences with flowers, borne on relatively short, erect or spreading pedicels. Photographs by Richard Boon.