Leonardoxa africana (Baill.) Aubrév.

Mckey, Doyle B., 2000, Leonardoxa africana (Leguminosae: Caesalpinioideae): a complex of mostly allopatric subspecies, Adansonia (3) 22 (1), pp. 71-109 : 96-102

publication ID

https://doi.org/ 10.5281/zenodo.4605796

publication LSID

lsid:zoobank.org:pub:933B60E6-57E6-4EB4-ACA8-D871ABD9F36A

persistent identifier

https://treatment.plazi.org/id/03E6A435-FFA6-FFDC-C269-718BA8B259C4

treatment provided by

Carolina

scientific name

Leonardoxa africana (Baill.) Aubrév.
status

 

1. Leonardoxa africana (Baill.) Aubrév. View in CoL subsp.

africana (= group 4)

Tree to 14 m tall. Trunk (rarely) to 40 cm diam., usually under 15 cm diam. Young shoots produced in flushes consisting of only a single internode and young leaf at each branch tip. Internodes of young twigs (2.5-)3.5-7.5(-9) cm long, modified as myrmecodomatia, swollen,

with thick pith except at base; twigs 4.3-5.7 mm diam. at apex tapering to ca. 2 mm diam. at base of internode; ant-cavities each a single internode long. Swollen internodes present from the seedling stage (20 cm tall) onward. Prostoma of ant-domatia at apex of internode opposite leaf insertion, elliptic. Leaves (2-)3(-rarely 4)-jugate. Leaflets elliptic, falcate, apex long-acuminate, the smallest leaflets (proximal pair) (7.8-)13(-15) cm long and (3.5-)5(-6) cm broad, the largest ones (distal pair in 2-jugate leaves, next-to-distal pair in 3- and 4-jugate leaves) (9.5-)15(-20) cm long and (4-)5.5(-7) cm broad; nectary glands large (smooth gland surface oblong, about 1 × 0.75 mm, surrounded by a raised ring of tissue about 1mm broad), consistently present on abaxial surface of each leaflet, with (2-)3-5 glands on each proximal leaflet, (1-)2(-3) glands on each median leaflet, and (0-)1-2 glands on each distal leaflet. Racemes to 4 cm long, with 40-50 flowers, usually cauliflorous, borne on main trunk and on large branches, or ramiflorous on twigs of ca. 5 mm diam. and larger. Flowers 1.8-2.2 cm in diam.; pedicels 2-4 mm long; calyx green or red, sepals 0.5-0.8 cm long; petals violet, purple, mauve, pink or red, 0.6-1.0 cm long. Ovules 4-5. Fruit oblongobovate, 8-11 cm long, 2.5-4 cm broad.

Leonardoxa africana subsp. africana is a highly specialised myrmecophyte, differing from the other myrmecophytic subspecies in a number of traits: (1) Foliar nectaries ( Fig. 5C View Fig ) are larger, more numerous, and less variable in presence/absence and number than in the other subspecies; (2) only a single leaf-bearing intern- ode is produced in each flush of growth at a branch tip, so that each ant-cavity is a single internode long ( Figs. 6B View Fig , 7B View Fig ); (3) growth of different branch tips is not synchronised over the crown of the tree; (4) specialised swollen internodes appear much earlier (seedlings 20 cm tall) in plant ontogeny than in the other subspecies; (5) the prostoma is elliptic-oblong rather than spherical in shape ( Fig. 6D View Fig ). Also, while cauliflory on old branches, or even on the trunk, occurs in all three myrmecophytic subspecies, it appears to be especially frequent in subsp. africana ( Fig. 8B View Fig ).

DISTRIBUTION. — Leonardoxa africana subsp. africana is restricted to coastal forests of Cameroon ( Figs. 3 View Fig , 4 View Fig ). All the field sites are below 80 m elevation. Judging from collection localities and notes on labels, this subspecies appears rarely to occur above about 100 m. The northernmost known localities are from the Southern Bakundu Forest Reserve , and the southern boundary of its range appears to be near Campo , at the border with Equatorial Guinea. Within this coastal strip, it extends inland as far as Bipindi, on the eastern edge of the coastal plain .

ECOLOGY. — This subspecies, illustrated in AUBRÉVILLE (1970), is the one that has attracted most attention as a myrmecophyte. The studies by ELIAS (1980), MCKEY (1984), GAUME et al. (1997) and GAUME & MCKEY (1999) all concern this subspecies. Internodes are swollen and hollow, and these ant-domatia are present already in seedlings 20 cm tall (see Fig. 2B View Fig in LÉONARD [1993]). This subspecies is associated with two ant species that are completely restricted to this host, the formicine Petalomyrmex phylax and the myrmicine Cataulacus mckeyi ( MCKEY 1984) . Petalomyrmex is a mutualist of the plant, protecting its young leaves against phytophagous insects ( GAUME et al. 1997), while Cataulacus is a parasite, providing no protection to the plant and excluding Petalomyrmex from plants it occupies ( GAUME & MCKEY 1999). This subspecies was termed “ L. africana taxon T4” by CHENUIL & MCKEY (1996).

Few observations of flower visitors have been made, but on a few occasions sunbirds were seen visiting the pink to red flowers, which in this subspecies at least seem to have a somewhat longtubular corolla, compared to flowers of the non-myrmecophytic subspecies (see below).

ADDITIONAL SPECIMENS EXAMINED. — CAMEROON,

Southwest Province: Southern Bakundu Forest

Reserve, E.W. Jones in Brenan 9499 (K, P), FHI 29511 (K), 29672 (K), and 41007 (K); Southern Bakundu Forest Reserve, 1 km W Bombe Bakundu, Manning 1499 (MO); Southern Bakundu Forest Reserve, near Kindonge Camp, Manning 1517 (MO); Kumba (planted in forestry nursery), FHI 29369 (K). Littoral Province: 24 km E Douala, Breteler et al. 2580 (BR, K, P, YA); Douala, route Razel, Endengle 2105 (P, YA); Douala, forêt de Yelfoume, Fleury, in herb. Chevalier 33346 (P); 14 km E Douala, Douala-Edea Road, Mpom 303 in part (BR); Lake Tissongo, Douala-Edea Forest Reserve, McKey & Gartlan 120 (K), D.W. Thomas 167 (YA), Waterman & McKey 846 (K); stream Mangombe near Edea, Mpom 343 (YA). Central-South Province: near Bipaga II, km 40 from Kribi to Edea, de Kruif 994 (WAG); Lolodorf Road, 12 km E of Kribi, Bos 3630 (BR, WAG, YA); 5 km N of Lolodorf road, 19 km E of Kribi, Bos 3913 (BR, YA); Lolodorf Road, 18 km E of Kribi, Bos 4074 (BR, YA); km 30 from Kribi to Ebolowa, Bos 6233 (WAG); km 45 from Kribi to Campo, Bos 7315 (BR); 60 km S of Edea, S of Mboke, 11 km E of km 58 from Edea to Kribi, Leeuwenberg 5500 (BR, K, MO, P, WAG, YA); colline Nkoltsia, Villiers 775 (P); near Bella, Letouzey 4140 (P, YA); 2 km from Nkol-Bewa, Mpom 227 (P, YA); Edoudouma, Mpom 283 (YA); Bipindi, Farron 7181 (BAS, P, YA), Zenker, s.n. (BR, P), 52 (WAG), 1074 (K, MO, P, WAG), 2967 (BR, K, WAG), 4183 (BR, K, P), 4495 (BR, K, MO).

2. Leonardoxa africana subsp. letouzeyi McKey , subsp. nov. (= group 3)

Haec subspecies Leonardoxae africanae subsp. africanae arcte affinis, sed ab ea medullae loculo per internodia duo triave continuo, foliorum expansione simultanea ramunculi ad nodos terminales duos tresve, glandulis nectariferis crateriformibus minoribus ac quoad numerum plus variabilibus (ad foliola proximalia plerumque nullis ad duabus) atque foliolis usque ad 30 cm longis utroque rhachidis latere saepe quattuor distinguitur.

TYPUS. — D. W. Thomas et al. 7480, Cameroon, Southwest Province, roadside forest S of Baro Village , 5º14’N, 9º15’E, 250 m, 31 Mar. 1988 (holo-, GoogleMaps MO; iso-, WAG).

Small tree, (rarely) to 14 m tall. Trunk to 30 cm diam. Young shoots produced in flushes consisting of (1-)2-3 internodes plus young leaves at each branch tip (in adult trees). Internodes of young twigs (2.8-)7(-13) cm long, modified as myrmecodomatia, swollen, with thick pith; twigs (4-)5.5(-6.1) mm diam. at apex tapering to ca. 2.5-4 mm diam. at base of internode; enlarged pith extending throughout section of twig produced in a single growth flush; ant-cavities each 2-3 internodes long (in adult trees). Swollen internodes absent in seedlings, present only in plants ≥ 60 cm tall. Prostoma of ant-domatia at apex of terminal internode of each flush of growth, opposite leaf insertion, roughly spherical in shape. Leaves (2-3-)4(-5)-jugate. Leaflets elliptic, falcate, apex long-acuminate, proximal ones (13.2-)17(-22) cm long and (4.5-)6(-8) cm broad, largest leaflets (next-to-distal pair) (14.5-) 21(-32) cm long and (5-)7.5(-12) cm broad. Nectary glands absent from some individuals; when present, appearing intermediate in size (smooth gland surface oblong, about 1 × 0.75 mm, not surrounded by a raised ring of tissue) and few in number, usually 0-2 (very rarely up to 5) on proximal leaflets and usually absent on other leaflets. Racemes short (axis 3-5 cm long), with 40-60 flowers, axillary on twigs of up to 1 cm diam., also sometimes cauliflorous. Flowers 1.8-3 cm diam.; pedicels 0.3-0.5 cm long; calyx pale lilac, sepals 0.8-1.1 cm long; petals usually violet, sometimes pink, 0.9-1.3 cm long. Ovules 4-5. Fruit to 15 cm long, 5 cm broad.

The most distinctive trait of L. africana subsp. letouzeyi is the large size of its stems and leaves ( Fig. 9C View Fig ). Young twigs are much more robust than those of corresponding age of plants of any of the other subspecies, leaflets are larger, and 4- jugate leaves predominate on most adult trees, in contrast to the 2-or 3-jugate leaves which characterise the other subspecies. Another trait distinguishing the subspecies letouzeyi from all other subspecies is the great variation among individual trees of the same population in the number of foliar nectaries. This subspecies shares with subsp. rumpiensis several traits that together distinguish them from subsp. africana : (1) Antcavities are first produced in juveniles over 50 cm tall; (2) ant-cavities in adult trees extend over 2-3 internodes, corresponding to the units of growth produced in flushes; (3) vegetative growth is synchronised over the crown of the tree; (4) the prostoma is roughly spherical in shape ( Fig. 6C View Fig ).

DISTRIBUTION. — This subspecies occurs in the wettest forests of Africa, the lowland forests near the Bight of Biafra ( Figs. 3 View Fig , 4 View Fig ). It is found from Uwet Division, Calabar Province, Nigeria, through Korup National Park on Cameroon’s border with Nigeria, and throughout the Mamfe Plain and Cross River area. Its range extends northward at least to the Takamanda Forest Reserve north of Mamfe. The eastern limit of its distribution is uncertain.

ECOLOGY. — This subspecies is a myrmecophyte in which swollen stems may first appear in juveniles about 60 cm tall (but more commonly in saplings 1 m or taller). While saplings are associated with small colonies of any of several species of twig-nesting ants, mature individuals are occupied solely by the formicine ant Aphomomyrmex afer , which protects young leaves of the host tree against insect herbivores (GAUME 1998; GAUME & MCKEY 1998). This subspecies was termed “ L. letouzeyi ” by MCKEY (1991) and “ L. africana taxon T3” by C HENUIL & M C K EY (1996), GAUME et al. (1998) and GAUME & MCKEY (1998). The ant occupants of this subspecies tend scale insects and mealybugs inside the hollow stems of the host (GAUME et al. 1998), in contrast to the ants associated with the subspecies africana , which never tend homopterans. (For the subspecies rumpiensis, more information is required on this point.) As argued by GAUME et al. (1998), this dependence on homopterans is related to the low and variable number of foliar nectaries in this subspecies.

PARATYPES. — NIGERIA, Uwet Division: Calabar River, Latilo 35 ( BR, K, P) ; Oban, Talbot 1440 ( K) . — CAMEROON, Southwest Province: Bamenda Road, Mile 43 from Mamfe , 1,500 ft (460 m), Coombe 191 ( BR, K) ; Akpasang River, Korup National Park, McKey 72 ( P, YA) ; Korup National Park, between Mana River bridge and Camp 1, Manning 1714 ( MO) ; disturbed forest near Ndian Oil Palm Plantation , 50 m, D. W. Thomas 4269 ( BR, US) ; Takamanda Forest Reserve, near Matene , 170 m, D. W. Thomas 4527 ( MO) .

3. Leonardoxa africana subsp. rumpiensis McKey , subsp. nov. (= group 2)

Haec subspecies Leonardoxae africanae subsp. letouzeyi perarcte affinis, sed ab ea glandulis nectariferis crateriformibus majoribus ac quoad numerum plus constantibus (ad foliola proximalia plerumque nullis ad duabus) atque foliolis utroque rhachidis latere plerumque duobus distinguitur.

TYPUS. — Letouzey 14577, Cameroon, Southwest Province, Dikome Balue, 4°55’N, 9°15’E, 35 km NNW Kumba, 1200 m, 24 Mar. 1976 (holo-, GoogleMaps P; iso-, K, YA).

Small tree, to 14 m tall. Trunk to 35 cm diam. Young shoots produced in flushes consisting of (1-)2-3 internodes plus young leaves at each branch tip (in adult trees) ( Fig. 7 View Fig ). Internodes of young twigs (3-)5.5(-11) cm long, modified as myrmecodomatia, swollen, with thick pith; twigs (3-)4(-5) mm diam. at apex tapering to ca. 2-3 mm diam. at base of internode; enlarged pith extending throughout section of twig produced in a single growth flush; ant-cavities each 2-3 internodes long (in adult trees). Swollen internodes absent in seedlings, present only in plants ≥ 50 cm tall. Prostoma of ant-domatia at apex of terminal internode of each flush of growth, opposite leaf insertion, roughly spherical in shape. Leaves 2 (-3)-jugate ( Fig. 9 View Fig ). Leaflets elliptic, falcate, apex acuminate to long-acuminate, smallest ones (proximal pair) (6.5-)16(-28) cm long and (2.7-) 6.5(-11) cm broad, largest leaflets (second pair) (7-)17.5(-30) cm long and (3-)7(-12) cm broad. Nectary glands of intermediate size (smooth gland surface oblong, about 1 × 0.75 mm, not surrounded by a raised ring of tissue), usually 2(0-5) on proximal leaflets ( Fig. 5 View Fig ), (0-)1(-2) on other leaflets. Racemes short (axis 3-5 cm long), with> 40-60 flowers, axillary on twigs 4-5 mm diam., also sometimes cauliflorous (on trunk up to 10 cm diam.). Flowers 1.8-3 cm diam.; pedicels 0.3-0.5 cm long; calyx colour unknown, sepals 0.8-1.1 cm long; petals mauve-pink to purple, 0.9-1.3 cm long. Ovule number unknown. Size of mature fruit unknown.

This subspecies is also a myrmecophyte; all trees possess swollen hollow internodes occupied by ants. As mentioned above, L. africana subsp. rumpiensis shares a number of traits with subsp. letouzeyi that distinguish these two from subsp. africana . It is distinguished from subsp. letouzeyi by its usually 2-jugate leaves ( Fig. 9 View Fig ), the smaller size of its leaflets and stems, the constancy in nectary number, and its restriction to piedmont and submontane forest (above 500 m and probably more commonly above 800 m).

DISTRIBUTION. — This taxon occurs in the Rumpi Hills ( Figs. 3 View Fig , 4 View Fig ), where it was studied in 5 field sites. Herbarium specimens from three other sites in the Rumpi Hills (see below) also appear to belong here. Material of myrmecophytic L. africana collected from submontane forest on another hill in the Southwest Province (Letouzey 13632 [K, P, YA], from a 960 m hill 55 km southwest of Mamfe) is tentatively placed in this subspecies.

ECOLOGY. — This myrmecophyte, in contrast to the two preceding subspecies, is restricted to submontane forest (and lowland forest transitional to it: “piedmont” [ THOMAS 1995]). As in the other myrmecophytes, internodes are hollowed and occupied by ants, and each adult tree is occupied by a single ant colony. In contrast to the two preceding subspecies, each of which is principally associated with one (or two) ant species, a diverse array of ant species occupy trees in populations of the subspecies rumpiensis (D. MCKEY and R. SNELLING, unpubl. results). Nature of the interactions with ants has not been studied in this subspecies. This subspecies was termed “ L. africana taxon T2” by CHENUIL & MCKEY (1996).

PARATYPES. — CAMEROON, Southwest Province : Steep hillside, 400-850 m, 5 km W of Esukutang Village, D. W . Thomas et al. 7988 ( MO); forest, 500 m, near Masaka- Batanga, D. W . Thomas & Namata 7746 ( MO); forest, 500 m, near Meta village , Nemba et al. 753 ( MO); colline, 960 m (près côte 897) E of piste Abakpa-Mbiofong , 55km SW Mamfe, Letouzey 13632 ( K, P, YA) .

W

Naturhistorisches Museum Wien

S

Department of Botany, Swedish Museum of Natural History

BR

Embrapa Agrobiology Diazothrophic Microbial Culture Collection

K

Royal Botanic Gardens

P

Museum National d' Histoire Naturelle, Paris (MNHN) - Vascular Plants

YA

National Herbarium of Cameroon

MO

Missouri Botanical Garden

E

Royal Botanic Garden Edinburgh

Kingdom

Plantae

Phylum

Tracheophyta

Class

Magnoliopsida

Order

Fabales

Family

Fabaceae

Genus

Leonardoxa

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