Kew Bulletin

, 64:129

Berlinia korupensis (Leguminosae Caesalpinioideae), a new tree species from Cameroon

Authors

    • Royal Botanic Gardens
  • Xander M. van der Burgt
    • Royal Botanic Gardens
Article

DOI: 10.1007/s12225-009-9100-z

Cite this article as:
Mackinder, B.A. & van der Burgt, X.M. Kew Bull (2009) 64: 129. doi:10.1007/s12225-009-9100-z

Summary

The tree species Berlinia korupensis Mackinder & Burgt is described as new. The species is endemic to the southern part of Korup National Park in Cameroon. Seventeen trees have been found so far, the largest being 42 m high and having a trunk diam. of 88 cm. The new species is assessed as Critically Endangered (CR D) under the criteria of IUCN. Two distribution maps are included; one map indicating the single locality in Cameroon near the Nigerian border where the new species was found and another map of the permanent plot where 14 of the 17 trees were recorded. A line drawing is also included, along with colour photographs of the flowers and the trunk.

Key words

BerliniaCameroonCaesalpinioideaeFabaceaegregariousKorup National Parknarrow endemic

Introduction

The southern part of Korup National Park (south Korup) in Cameroon is covered by lowland rainforest. The environment is fairly uniform: the topography is flat or gently sloping and the soils are sandy with a substrate of crystalline rocks. The overall physiography is rather uniform. However, the tree species composition is much less uniform, as many species grow gregariously, that is they are abundant in some parts of the forest but absent in others. Numerous western and central African tree species from the legume subfamily Caesalpinioideae are known to grow gregariously (Aubréville 1968; Letouzey 1968; Wieringa 1999) and in south Korup Tetraberlinia bifoliolata (Harms) Hauman, T. korupensis Wieringa and Microberlinia bisulcata A. Chev. are well documented as doing so (Newbery et al. 1998). At least two caesalpinioid tree species (T. korupensis and Englerodendron korupense Burgt) are endemic to south Korup. Our new species Berlinia korupensis is a third example of a gregarious caesalpinioid tree species that is endemic to the rainforests of south Korup.

In January 2003, during the establishment of a permanent plot in primary lowland rainforest in south Korup, the first trees of the new species were registered. The leaflets and flowers collected from the ground in April that year (later made into the collection van der Burgt & Eyakwe 822) were compared at WAG and given a preliminary identification of Berlinia confusa Hoyle. In April 2005, a flowering collection was made (van der Burgt 756) along with some photographs. On examining the photographs, one of which is shown as Fig. 2A, the first author concluded that the material did not match B. confusa, but instead represented a species new to science. In October 2005, pods were collected from the same tree (van der Burgt 780).

To distinguish Berlinia korupensis in flower from other species, an abbreviated key is provided. Based on relative size of petals, there are three different petal arrangements found in Berlinia, so for ease of use, the first division of the key is a trichotomy.

Abbreviated key based on floral characters to distinguish Berlinia korupensis from other species of Berlinia

  • 1a. Adaxial petal c. 1 – 3 cm longer than the lateral and abaxial petals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

  • 1b. All petals of subequal length; bracts 45 – 120 mm long . . . . . . . . . . . B. occidentalisKeayor B. bracteosaBenth.

  • 1c. Adaxial petal much longer and wider than the lateral and abaxial petals, the smaller petals not longer than the length of the claw of the adaxial petal; bracts caducous, seldom seen, not exceeding 5 mm long . . . . . . . . . . . . B. auriculataBenth., B. bruneelii (De Wild.) Torre & Hillc., B. confusa, B. congolensis (Baker f.) Keay, B. coriaceaKeay, B. craibiana Benth. B. giorgiiDe Wild., B. grandiflora (J.Vahl) Hutch. & Dalziel, B. hollandiiHutch. & Dalziel, B. lundensisTorre & Hillc., B. orientalisBrenan, B. phenacoaMackinder, B. rabiensisMackinder, B. sapiniiDe Wild., B. tomentellaKeay, B. viridicansBaker f.

  • 2a. Bracts 7 – 12 mm long, falling before anthesis; known only from Cameroon . . . . . . . . . . . . . . . . . B. korupensis

  • 2b. Bracts 22 – 40 mm long, persisting after anthesis; known only from Gabon . . . . B. razziferaMackinder & Wieringa

Berlinia korupensisMackinder & Burgtsp. nov.B. razziferae Mackinder & Wieringa affinis sed bracteis late triangularibus (nec ovatis) minoribus 7 – 12 × 4 – 5 mm (nec 22 – 40 × 14 – 20 mm), multo breviore tempore caducis atque in inflorescentia immatura conspicuis (nec ad anthesin neque post lapsum florum persistentibus), bracteolis tenuis (nec crassis) angustioribis c. triplo longioribus (nec c. duplo tantum longioribus) quam latioribus atque intus partim dense sericeis (nec glabris neque sparse puberulis), ovariis brevioribus c. 7 mm (neque 12 – 15 mm) longis sericeis (nec ± glabris margine pubescenti excepta) vel B. confusae Hoyle affinis sed rachide foliorum sparse vel modice puberulis (nec glabris), venis secundariis et supra et infra visibilibus (nec indistinctis), bracteis triangularibus ad basin 7 – 12 mm (nec 2 mm) latis atque in inflorescentia immature conspicuis (nec inconspicuis in inflorescentiis perjuventibus tantum visis atque mox caducis, pagina interiora bracteolarum omnino glabra (nec partim dense puberula), superficie hypanthia irregulariter pubescenti atque inter vittiis longitudinalibus pilorum manifesta (nec superficie glabra neque pubescentiam sparsam dispersam raro densiorem ferenti), sepalis c. 7-plo (nec c. 5-plo) longioribus quam latioribus, petalis lateralibus atque abaxialibus inter se similibus, omnes 27 – 38 × 8 – 10 mm (nec dissimilibus lateralibus 7 – 17 × 3 – 4 mm, abaxialibus 7 – 12 × 2.5 – 3 mm), atque ad apicem emarginatis interdum in medio sinus lobatis (nec ad apicem integris, ovario c. 7 mm (nec 10 – 12 mm, longo) differt. Typus: Cameroon, SW Province, Korup National Park, NW Plot near P transect, van der Burgt 756 (holotypus WAG; isotypi BR, G, K, MO, P, SCA, YA).

Tree up to 42 m tall; dbh up to 88 cm; crown a half sphere up to 30 – 35 m diam.; bole straight, buttresses 20 – 30 cm thick, up to c. 1.5 m high and extending out to c. 0.7 m, bark whitish light brown, smooth but sometimes flaky, with flakes detaching in groups to leave shallow scars, in a more or less concentric pattern. Stipules not seen, falling early but base leaving an intrapetiolar rim. Leaves alternate, paripinnate, petioles 2.3 – 5.3 cm long, rachises 1.8 – 13.2 cm long, sparsely to moderately puberulous, the indumentum just visible at ×10 magnification; petiolules 6 – 10 mm long; leaflets in 2 – 4 pairs, occasionally only one of a pair of leaflets developing; the upper pair opposite, the lower pairs opposite or subopposite, narrowly ovate, narrowly elliptic or narrowly obovate, slightly falcate, concolorous, drying dull green, 8.3 – 15 × 3.4 – 6.3 cm, sparse to moderately puberulous, the indumentum just visible at ×10 magnification, secondary veins in 9 – 13 pairs, the tertiary veins visible above and below, apex acute or short-acuminate, acumen to 5 mm long, base rounded or cuneate. Inflorescence a cluster of 2 – 3 racemes, occasionally branching once, axes densely puberulous, peduncle and rachis together 8.5 – 15.2 cm long. Hermaphrodite flowers: pedicels 10 – 21 mm long. Bracts broadly triangular, 7 – 12 × 4 – 5 mm, conspicuous in developing inflorescence but not persisting until anthesis, Bracteoles thin, obovate, 28 – 40 × 9 – 12 mm, about three times longer than wide, outer surface densely puberulous, inner surface densely puberulous when newly opened, but later becoming glabrous in the central area. Hypanthium tubular, 9 – 12 mm long, unevenly pubescent outside, the surface clearly visible between irregular longitudinal bands of hairs, glabrous inside. Sepals 5, subequal, narrowly oblong, 22 – 28 × 3 – 4 mm long, petaloid, striate, glabrous. Petals 5, unequal in length; adaxial petal largest, 48 – 55 × 35 – 40 mm, apex emarginate; lateral and abaxial petals smaller and all similar in size, narrowly oblong becoming wider towards the apex, 27 – 38 × 8 – 10 mm, apex emarginate to entire. Stamens 10, 9 fused at base for 2 – 3 mm, free part of filaments 43 – 55 mm long, anthers c. 2.5 mm long, adaxial stamen free. Ovary shortly stipitate, oblong, c. 7 × 2 mm, faces densely sericeous, individual hairs clearly visible at ×10 magnification, style 41 – 48 mm long, stigma terminal, capitate, minute. Functionally male flowers1 occasionally present, resembling the hermaphrodite flowers, bracteoles 6 – 11 × 4 – 7 mm; hypanthium, 1 mm long; sepals 4 – 6 × 1 – 2 mm; adaxial petal 2 – 5 × 3 – 4 mm; stamens free part of filaments 2 – 3 mm long, anthers 1 – 1.5 mm long; ovary 2 – 2.5 × c. 1 mm, style coiled, 1 – 2 mm long. Pod oblong, laterally compressed, 15 – 33 × 6 – 9 cm, moderately golden puberulous during maturation, dehisced mature valves appearing glabrous at ×10 magnification but minutely, sparsely and unevenly puberulous at higher magnification, outer surface dull, transverse grooves visible, upper suture to 8 mm wide on each valve, beak to 18 mm long. Seeds not seen, but 1 – 4 positions in pods. Seedling: hypocotyl very short; cotyledons at ground level, spreading, fleshy; leafless part of stem 24 – 32 cm long, with a few linear scales present; leaves (1 –) 2 (– 3), alternate, stipulate, pinnate; leaflets opposite, usually 2 pairs, sometimes 1 pair or a single leaflet only; petiole 3.8 – 7.1 cm long, rachis (0 –) 2 – 3.6 cm long; petiolule 0.4 – 0.6 cm long; leaflets ovate to elliptic, 7.5 – 13 (– 16.5) × 3.5 – 5.5 (– 7.5) cm, secondary nerves 5 – 6 pairs, apex long acuminate, acumen 2 – 3.5 cm long. Figs 1 & 2.
https://static-content.springer.com/image/art%3A10.1007%2Fs12225-009-9100-z/MediaObjects/12225_2009_9100_Fig1_HTML.gif
Fig. 1

Berlinia korupensis. A flowering branch; B flower; C leaflet showing lower surface; D close-up of upper leaflet surface; E close-up of lower leaflet surface; F section of hypanthium outer surface showing indumentum; G bracteole showing thickness and internal surface; H ovary showing indumentum; J dehisced coiled valve of pod; K close-up of dehisced valve surface. AH from van der Burgt 756, JK from van der Burgt 780. drawn by margaret tebbs.

https://static-content.springer.com/image/art%3A10.1007%2Fs12225-009-9100-z/MediaObjects/12225_2009_9100_Fig2_HTML.jpg
Fig. 2

Berlinia korupensis. A flower (van der Burgt 756); B base of a tree of 71 cm trunk diam. at 1.3 m high. photos by xander van der burgt.

Distribution. Africa: Cameroon.

Specimens Examined. Cameroon. SW Province: Korup National Park, NW Plot near P transect, subplot 38NN, tree number NW0329, fl. 28 April 2005, van der Burgt 756 (holotype WAG; isotypes BR, G, K, MO, P, SCA, YA); same tree, fr. 18 Oct. 2005, van der Burgt & Eyakwe 780 (BR, G, K, MO, P, SCA, WAG, YA); NW plot near P transect, subplot 37JN, tree number NW0262, fl. 15 April 2003, van der Burgt & Eyakwe 822 (SCA, WAG); NW plot near P transect, subplot 43LN, tree number NW0808, fl. & fr. 27 May 2007, van der Burgt, Motoh, Njibili & Elangwe 948 (BR, G, K, MO, P, SCA, WAG, YA); same tree, seedlings 20 Feb. 2008, Pearce et al. 7 (BR, G, K, MO, P, SCA, WAG, YA). All collections at 5°01′N; 8°47′E. Map 1.
https://static-content.springer.com/image/art%3A10.1007%2Fs12225-009-9100-z/MediaObjects/12225_2009_9100_Fig3_HTML.gif
Map 1

Distribution map of Berlinia korupensis (●).

habitat & ecology. Primary rainforest on well-drained sandy soil; c. 100 m. The rainfall at the Bulu weather station, c. 12 km SE of the type locality, ranged from 4023 to 6146 mm/y, and averaged 5061 mm/y (1984 – 2007). The climate is strongly seasonal with one distinct dry season from December to February (average monthly rainfall less than 100 mm).

Berlinia korupensis has only been found within and near to the “NW plot”, which occupies an area of 56.25 ha and is situated near the “P transect” in the Caesalpinioideae-rich forest of south Korup. It is absent from the nearby “P plot”, which occupies an area of 82.5 ha and is situated just SE of the NW plot, in the same forest type. The species is also absent from the 50 ha “KFDP plot” (Kenfack et al. 2006), which is situated in Caesalpinioideae-poor forest at 11 km to the northeast of the P and NW plots, but still within Korup National Park.

The NW plot is completely covered in primary rainforest, and is on flat or slightly sloping ground at about 100 m asl. The difference in altitude between the lowest and the highest point is 16 m. Within the NW plot, 1194 trees of ≥ 50 cm trunk diam. were registered of which 13 were identified as Berlinia korupensis. Trees with smaller trunk diameters of between 10 – 50 cm diam. were recorded from 23 randomly located subplots within the NW plot (size 0.25 ha per subplot; total size 5.75 ha) but of the 2587 trees registered, none were identified as B. korupensis. Still inside the NW plot but not within any of the 23 subplots, an additional tree was recorded but at 48.4 cm diam. it fell just below the 50 cm trunk diam. criterion. Precise mapping of the 14 individuals from the NW plot indicates that B. korupensis grows gregariously on well-drained sandy soils and avoids areas immediately adjacent to streams and gullies which become periodically inundated (Map 2). A further three trees have been found by chance, close to the northern edge of the NW plot, bringing the total to 17. It is almost certain that more trees of B. korupensis occur there because the area is not yet extensively explored.
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Map 2

Distribution of 14 trees of Berlinia korupensis in the “NW plot” in south Korup National Park. The size of a dot represents the trunk diam. of the tree, at 1.3 – 3.4 m height, categorised in five size classes: 40 – 50, 50 – 60, 60 – 70, 70 – 80 and 80 – 90 cm respectively. The plot contains 1194 trees of over 50 cm trunk diam., of which 13 are B. korupensis. A single tree in the smallest size class of 40 – 50 cm was registered by chance. The widest lines represent small streams; thinner lines represent gullies; the thinnest lines represent the edges of periodically inundated areas.

As is the case for all species of Berlinia, and indeed many other caesalpinioid genera, the seeds of B. korupensis are dispersed by explosive pod dehiscence (van der Burgt 1997). When a mature pod is exposed to sunshine or dry air, it begins to dry. The two drying valves of the pod are predisposed to curl up in different directions, and as a result tension builds up between them. The corky connecting layer between the two valves keeps them attached and thereby flat, but as the drying continues, the tension eventually becomes too large and the pod dehisces suddenly and forcefully. The two valves twist rapidly, in opposite directions, and the seeds are ejected at speed. Many seeds drop beneath the crown of the parent tree, but some are dispersed to short distances from the edge of the crown. The maximum explosive dispersal distance is unknown but we speculate that it is probably in the range of 30 – 50 m. It is also unknown if there is any secondary dispersal e.g. by animals or by rivers. The relatively short and strictly limited maximum explosive dispersal distance is presumed to be a contributory factor to grove-formation (Wieringa 1999).

Conservation. Berlinia korupensis is assessed here as Critically Endangered (CR D) under the criteria of IUCN (2001). This species is known from only 17 individuals at a single location within a protected area.

Etymology. Named after Korup National Park within which all known individuals of this species are located.

Notes. A striking feature of the flowers of van der Burgt 756 is the size of the lateral and abaxial petals which are neither as long as the well-developed adaxial petal (as is the case in Berlinia occidentalis Keay and B. bracteosa Benth.) nor very much shorter (as is the case in the majority of Berlinia species). In B. korupensis the abaxial and lateral petals are intermediate in size between these extremes. B. razzifera is the only other species in the genus that possesses the intermediate petal form.

Formerly two generic sections were recognised within the genus but as a consequence of the recent discovery and description of new species, especially Berlinia razzifera and now B. korupensis justification of two sections based on gross morphology has become untenable. In particular, the combination of morphological characters presented by these two species has eroded the distinction between the two sections. Furthermore, the results of a phylogenetic analysis based on nucleotide sequence data of the Internal Transcribed Spacer region (unpublished data) failed to recover the morphologically delimited sections and so they are no longer upheld.

Footnotes
1

The functionality of these flowers is hypothesised here as the viability of the pollen is not known.

 

Acknowledgements

The authors would like to thank Prof. David Newbery of the Institute of Plant Sciences, University of Bern, who supervised the ecological research that lead to the discovery of the present new species. The field research was funded by the Swiss National Science Foundation (Grant 3100-066655 to Prof. Newbery), and coordinated by Dr G. Chuyong. Three funds of the Royal Botanic Gardens, Kew, the Donations fund, the OFC fund and the Bentham-Moxon fund, also funded the collection of specimens and data. We thank the Cameroon government for permission to carry out research in Cameroon, and Korup National Park (Conservator, A. Kembou) for access to the site. We also thank the National Herbarium of Cameroon (Head, J.-M. Onana) for cooperation. Moses Elangwe climbed the tree from which the holotype was collected. Wolfgang Bischoff, Motoh Jackson, Sylvanos Njibili and Charles Okha provided field assistance. We would also like to thank Margaret Tebbs for preparing the illustration and Melanie Thomas for translating the Latin diagnosis.

Copyright information

© The Board of Trustees of the Royal Botanic Gardens, Kew 2009