Eriolaena rulkensii Dorr, 2018

Dorr, Laurence J. & Wurdack, Kenneth J., 2018, A new disjunct species of Eriolaena (Malvaceae, Dombeyoideae) from Continental Africa, PhytoKeys 111, pp. 11-16 : 12-13

Eriolaena rulkensii Dorr sp. nov. Figures 1 , 2

Helmiopsiella sp. A: Burrows et al., Trees shrubs Mozambique: 590. 2018.

Diagnosis.

Differs from Eriolaena wallichii DC. in having entire or sparingly toothed epicalyx bracts (versus laciniate epicalyx bracts) and an androecium of 10-15 anthers alternating with 5 staminodes (versus an androecium comprised of numerous stamens and no staminodes).

Type.

Mozambique. Cabo Delgado: Pemba, close to Pemba Bay, near Chibuaburare, 12°58'26"S, 040°30'10"E, 9 m alt., 23 Feb 2014 (fl, fr), A.J.H. Rulkens 1 (holotype: US-01184177; isotypes: BNRH, K-0001291030, K-0001291031, LMA, US-01184178).

Description.

Shrubs or straggly trees, 2-6 m tall. Bark smooth, mottled grey and brown; young stems with scattered, appressed multi-radiate stellate hairs; older stems lenticellate, ± glabrescent. Leaves simple, alternate, petiolate, stipulate; leaf blades ovate to broadly ovate, 7 –12.5(– 14) cm long, 5 –9(– 9.5) cm wide, apices long acuminate, bases cordate to truncate, margin coarsely crenate except base of blade entire, (3-)5-nerved from the base, primary, secondary and tertiary nerves clearly visible below, veinlets visible below with 10 × magnification, ± glabrous above and below except for scattered minute multi-radiate stellate hairs that are more numerous on the primary and secondary nerves and toward leaf base, somewhat lustrous above, matt below; domatia absent; petioles 3 –4.5(– 7) cm long, sparingly pubescent with scattered minute multi-radiate stellate hairs; stipules long acicular, 9 –12(– 15) mm long, ca. 1 mm wide at base and tapering to 0.25 mm below apex, sparingly pubescent with scattered minute multi-radiate stellate hairs, caducous. Inflorescence paniculate, axillary and terminal, lax, 20-27 cm long, 20-25 cm wide; pedicels to 9(-10) cm long. Epicalyx bracts 3, acicular, 7-10 × 2 mm, entire or sparingly toothed apically, ± evenly spaced around the axis in bud, but clustered on one side at anthesis, caducous. Calyx 5-lobed, valvate, shortly (1.5-2 mm) connate at base, lobes lanceolate, 7-8 × 2 mm, apices acute, somewhat thickened distally, sparingly pubescent externally with appressed, minute multi-radiate stellate hairs, glabrous internally, smooth (i.e. nerves not visible). Petals 5, broadly obovate, 14 –16(– 22) mm long, 14 –15(– 20) mm wide, ± symmetrical, apices crispate, bases cuneate, bright yellow in vivo, glabrous externally and internally. Androecium of 10-15 anthers alternating with 5 staminodes; anthers in an outer whorl, borne in fascicles of 2(3), common filaments ca. 3-3.25 mm long, glabrous; anther sacs 2-2.25 mm long; staminodes in an inner whorl, ligulate, 10 × 1 mm, glabrous. Style 1, ca. 4 mm tall; stigmas 10, recurved apically, pale yellow to white. Fruit a loculicidally dehiscent capsule, obovoid, ± 1.5 cm in diameter, 10-ridged, sparingly pubescent with scattered minute multi-radiate stellate hairs, eventually splitting into separate mericarp-like structures. Seeds 1(2) per locule, obovate, 4 × 2 mm, laterally flattened, glabrous, each seed with a narrow, ca. 1 mm wide, hyaline, dorsal and apical wing.

Etymology.

Named for A.J.H. (Ton) Rulkens, an agronomist who works for OXFAM Belgium to strengthen small-scale farmer organizations in Cabo Delgado province, Mozambique. Rulkens is also a keen amateur botanist and photographer who has made many interesting plant discoveries in Mozambique, especially amongst representatives of the succulent flora ( McCoy et al. 2014, 2017; McCoy and Baptista 2016).

Distribution and ecology.

Endemic to northern Mozambique where it is known from several localities on the eastern and southern shore of Pemba Bay (Baia de Pemba) near the city of Pemba where it occurs on heavy clay over coral-rag in coastal scrub at the upper margin of mangrove communities ( Burrows et al. 2018); ca. 10 m alt. According to Rulkens (personal communication), Ernst Schmidt observed the shrub between Macomia and the coast in 2009 but later discovered the plant had been cut down. Rulkens also observed additional locations with many plants about 10 km from Pemba in small patches of coastal forest on fossil coral substrate.

Threats.

Eriolaena rulkensii is exploited for firewood (fide Rulkens 1, in sched.) and, on a different scale, it is threatened because the coastal forests and woodlands of northeast Mozambique are subject to increased development following the instability resulting from the independence and civil wars ( Timberlake et al. 2011). Eriolaena rulkensii is only one of many new species discoveries and new records from the Cabo Delgado area of Mozambique, others of which are enumerated by Timberlake et al. (2011).

Figures

Figure 1. Eriolaena rulkensii. A Habit B, C Flower buds with 3 epicalyx bracts each D Immature flower with petals (yellow), sepals (green) and scar of one dehisced epicalyx bract E Detail of sepal F Flower at anthesis showing petals, anthers, staminodes and gynoecium G Detail of petal H Detail of androecium showing androecial tube, anthers in fascicles and staminodes I Gynoecium and base of two staminodes J Immature capsule showing scars from dehisced calyx lobes and epicalyx bracts. (Source: A. J. H. Rulkens 1, US).

Figure 2. Eriolaena rulkensii. A Trunk and bark B Infructescence C Immature capsules with prominent ridges D Habit (shrub in centre with yellow flowers) E Flower (foreground) with stamens in fascicles of 2 (3), each alternating with a ligulate staminode, and a simple style with 10 stigmas; flower buds (background) with 3 epicalyx lobes subtending each calyx F Capsules (mature) with loculicidally dehiscent mericarp-like structures. Photographs: A. J. H. Rulkens.