Pavetta sapoensis W.D.Hawth.

Hawthorne, W.D. (2003). Six new Pavetta (Rubiaceae), including three ‘litter-bin’ species from the evergreen forests of Western Africa. Kew Bulletin 68: 559. https://doi.org/10.1007/s12225-013-9484-7

Type

Type: Liberia, Sino: Sapo National Park, in buffer zone close to E end of Babooni road, 5°29.3'N, 8°35.8'W, alt. 170 m, 27 Nov. 2002, Jongkind, Blyden, staff and students of the University of Liberia 5464 (holotype WAG (sheet WAG0070690 late flowering/early fruit); isotype WAG (sheets WAG0070689 sterile, WAG0070691 fruiting)).

Morphology General Habit

Shrub 1 m high

Morphology Stem

Erect main stem with short flowering branchlets in the leaf axils

Morphology Branches

Branchlet and petiole glabrous; youngest internodes channelled

Morphology Leaves Stipules

Stipule triangular, leathery, c. 4 mm long × 5 mm wide, glabrous inside and out

Morphology Leaves Petiole

Petiole very short (1 – 9 mm) relative to lamina, collecting much debris around the leaf bases

Morphology Leaves

Lateral nerves 15 – 30 pairs, but the most basal short and usually crowded, interspersed with parallel tertiary veins, hence difficult to enumerate precisely; arching and joining the next lateral nerve either directly, especially in the lower half of the leaf, or after forking into two or more tertiary scalariform veins, forming a looping sub-marginal nerve; impressed to prominent above, prominent and drying reddish brown below. Tertiary veins obscure, impressed or prominent above, prominent below, scalariform (usually 4 – 10 linking adjacent laterals) or perpendicular to midrib and joining the steeply ascending lateral nerves Midrib flat or prominent above Leaves oblanceolate to lyrate, acuminate, 12 – 40 cm long × 2.5 – 8.5 cm wide, glabrous throughout; base rounded to cuneate, then decurrent Leaf arrangement ternate, but with more than three leaves and stipules clustered around a node when the contracted flowering branchlets are present in the leaf axils, the slender inflorescences emerging from this cluster Fourth order and finer (to sixth order) venation very finely prominent on both surfaces of dried leaves, slightly anisotropous (LVA <2, similar to P. ixorifolia and P ankasensis and not strongly anisotropous like P quasidigita); 12 – 31 veins per cm

Morphology Reproductive morphology Inflorescences

Inflorescence appearing axillary, two per node, but terminal on short (< 2 cm) axillary flowering branchlets, much shorter than the subtending leaves; peduncle 2 cm, slender up to the main sheathing bracts at the primary inflorescence node; axes puberulous with sparse, short hairs 0.05 – 0.2 mm long; sheathing bracts glabrous, rather leathery, triangular-acute, c. 3 mm long

Morphology Reproductive morphology Flowers

Flower fragrant and pale green (collector’s note)

Morphology Reproductive morphology Flowers Calyx

Calyx c. 1 mm long, tube c. 0.1 mm, lobes 0.2 – 0.4 mm

Morphology Reproductive morphology Flowers Corolla

Corolla 7 – 9 mm long (one shrivelled specimen), lobes 5 – 6 mm long; tube 2 – 3 mm long. Fruiting pedicels 1 – 5 mm long

Morphology Reproductive morphology Fruits

Fruit globose, 7 – 10 mm diam. when dried, almost black when mature (fresh or dried); immature fruits with 4 triangular calyx lobes c. 0.3 mm long; 1 – 4 seeds

Morphology Reproductive morphology Seeds

Seed varied in shape depending on number (mature seeds not examined, to retain integrity of the fruit in the type specimen)

Note

Differs from other Pavetta species by having large, sub-sessile ternate leaves, glabrous below; very short flowering branchlets congested in the leaf axils and very slender pedicels. See key above for differences from other litter-bin species.

Although the ternate leaves are unusual in Upper Guinean Pavetta species, they do occur occasionally on P. ixorifolia (W. D. Hawthorne et al. C3PG283 of P. ixorifolia has two whorls: one whorl with flowering branchlets and no leaves, the other with leaves only). Whorls might therefore be expected occasionally in our other two litter-bin species, which show some affinity with P. ixorifolia. The flowers are recorded by the collector as fragrant, pale green, 4-merous with dark anthers, but the three sheets of Jongkind et al. 5464 have only old flower parts, so it is assumed that most had fallen prior to reaching the herbarium. This species was not included in Hawthorne & Jongkind (2006) as the specimen was not known to the author at the time of writing. It keys to the Pavetta ixorifolia group (61.f) on page 592, where it can be readily distinguished from P. ankasensis and P. quasidigita using the key to litter-bin species above. Pavetta ankasensis and P. quasidigita also have some affinity with P. ixorifolia (subgenus Baconia, series glaberrimae), although P. ixorifolia lacks the distinctive litter-bin habit. Similarities can be found in the finely prominent venation (but details differ), usual lack of obvious bacterial nodules, whitish fruits with small calyx lobes appressed and subvalvate at the impressed, green fruit apex; and in inflorescence form and arrangement. One specimen of P. ankasensis shows the unusual dark blue-stained venation commonly seen in P. ixorifolia specimens. Bremekamp stated that Pavetta ixorifolia has only two ovules per locule, but some specimens from Ghana have three seeds (no 4-seeded fruits seen yet), as do P. quasidigita and P. sapoensis. Ovule number is an awkward key character to use, because as noted for P. sonjae it is very common, even normal that on a given plant only one or two ovules develop into seeds. Too few fruits of P. ankasensis are known, but it seems even closer to P. ixorifolia than the other two litter-bin species. If they prove to be closely related, these would then represent a third group of species in the genus with two ovules per locule (the others include P. lasioclada and P. sonjae (above); and P. tetramera (Hiern.) Bremek. and P. wildemanniiBremek., in section Dizygoon of subgenus Pavetta ). Specimens of our litter-bin plants with only 1 – 2 seeds, and therefore assumed to have one ovule per locule, would probably lead to P. puberula in subgenus Baconia, series puberulae using Bremekamp’s key, but none of these species appears to be closely related. P. camerounensis S. D. Manning from Lower Guinea is also similar to P. ixorifolia: both differ from our litter-bin species by their longer, often horizontal and tremulous, flowering shoots. P. camerounensis subsp. brevirama S. D. Manning has shorter branches than subsp. camerounensis, but the leaf bases and habit are still significantly different. Although the litter-bin species form an interesting functional group, and show various points of similarity with Pavetta ixorifolia, it is possible that they are not closely related, as there are significant differences between them. The litter-bin habit and similar morphology has evolved repeatedly in other Rubiaceae, most notably in species of the related genus Ixora.

Named after the type locality.

Distribution

Africa: Liberia

Conservation

Endangered (IUCN 2001). As Pavettasapoensis is known only from one collection in Sapo National Park, it could also qualify for Data Deficient IUCN status. Sapo NP is a large, legally protected area that is not thoroughly explored botanically; however, the species is distinctive, and if it were widespread or common elsewhere in Liberia or Ivory Coast it would surely have been collected more often. Endangered status is therefore a conservative categorisation, pending more precise surveys in Sapo and elsewhere which could lead to Critically Endangered status if it is indeed so rare.

Phenology

Fruit (and possibly still flowering — see notes) in November.