Lepeostegeres Blume

9 species of Malaya, Sumatra, Borneo, Celebes, Philippines east to New Guinea

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1 species recorded from New Guinea. Click on a name to go to its species page

1. L. deciduus Barlow. Eastern New Guinea

Description (Barlow 1993)

Lepeostegeres Blume in J.A.Schultes & J. Schultes, Syst. 7, 2 (1830) 1611, 1731. - Type: L. gemmiflorus Blume.

For descriptions and synonymy see Danser, Bull. Jard. Bot. Buitenzorg m, 11 (1931) 258; Philipp. J. Sci. 58 (1935) 30; Barlow, Austral. J. Bot. 22 (1974) 550.

A genus of 9 species distributed from Malaya, Sumatra, Borneo, Celebes, and Philippines eastwards to New Guinea. The major centre of species richness and diversity is Borneo (see below).

The species are found in a range of habitats from lowland rain forests to montane and subalpine forests up to 2800 m. Leaf architecture is not very variable, always decussate, usually simple and bifacial, and with pennate venation. The inflorescence architecture is similarly very homogeneous, and most variation is in dimensions of inflorescence and flower parts.

Diagnostic features
The infrafamilial classification of Lepeostegeres and the generic group to which it belongs is outlined above. For identification at the generic level the readily observable morphological characters are derived from inflorescence and flower structure.

The basic inflorescence unit (uniflorescence) in Lepeostegeres is a simple dichasium (triad) with a simple bract subtending each flower. The triads are aggregated into conflorescences, and the characteristic state for the genus is an axillary raceme of 6-12 opposite pairs of triads which are crowded into a dense capitulum on the flattened apex of a contracted axis. The capitulum is subtended by a series of enlarged, decussate, imbricate, rigid bracts, which tightly enclose the young flowers during development, and usually contribute to the visual presentation of the flowers after anthesis.

The flowers of Lepeostegeres are hennaphrodite, 6-merous, regular, and gamopetalous to near the middle. The epipetalous stamens have basifixed immobile introrse anthers with simple filaments which vary considerably in length between species. The process of anthesis is unusual and characteristic of the genus, with the corolla lobes becoming S-shaped at their point of reflexion prior to their separation from each other, and usually separating downwards before the lobes finally split apart at the apex. The style is usually articulate above the base, leaving a distinct nipple on the fruit.

The genus most confused with Lepeostegeres is Lepidaria. Both genera have capitate inflorescences of similar appearance, with the flowers subtended by enlarged, rigid, imbricate, decussate bracts. The similarity is most probably the result of a striking convergence, and the affinities of Lepidaria are probably with the elytranthoid genera discussed in the introduction. In Lepidaria the flowers are single rather than in triads, and each flower is subtended by one of the involucral bracts and also by two smaller but nevertheless enlarged concave bracteoles. In Lepidaria there are usually 4-6 and nonnally no more than 12 flowers in the head, whereas inLepeostegeres there are rarely as few as 8 and mostly more than 12.

Danser (1931) gave some emphasis to the 'apical spot' as a diagnostic character at species level. The apical spot, when present, is a scaly or differentially coloured mark on the outside of the involucral bract, near the apex. In the materials studied the apical spot has been found to be variable in expression and shape. Sometimes it appears as a medial band widening upwards. It is unreliable as a diagnostic character and has not been used in this treatment.

Generic relationships
Lepeostegeres ranks second among the decaisninoid genera in size, and therefore represents a distinct evolutionary pulse. Its capitate inflorescence subtended by a welldeveloped involucre is clearly a derived state, probably as an adaptation for protection and presentation of the flowers (see note under Decaisnina). Other genera with capitate inflorescences (such as Lepidaria and Thawnasianthes) have different inflorescence architecture, and there has been considerable convergence with respect to this state (see above). Lepeostegeres may be as close phylogenetically to Decaisnina or Amylotheca as it is to any of the other capitate genera.

Biogeographic history
For a general outline of the history of the decaisninoid genera, see note under Decaisnina. With its strong centre of diversity in Borneo, and limited representation in adjoining areas, Lepeostegeres has most probably originated in western Malesia, and undergone considerable differentiation prior to the establishment of Charles's Line (Barlow, 1990). Representation of the genus to the east of Charles's Line by a solitary species in New Guinea indicates a very limited representation in the intrusive Malesian stocks which penetrated New Guinea. In this respect the genus shows a close parallel to Macrosolen (Barlow, 1990).

1a. Involucral bracts acute, sagittate (Philippines) 1. L. acutibracteus
1b. Involucral bracts obtuse to rounded, not sagittate. 2
2a. Involucral bracts deciduous after anthesis 3
2b. Involucra! bracts persistent. 4
3a. Flowers and fruits sessile (New Guinea) 7. L. deciduus
3b. Flowers pedicellate, the pedicels elongating under the fruits (Philippines) 6. L. congestiflorus
4a. Leaves long-acuminate and acute at the apex 5
4b. Leaves acute to rounded at the apex, but not long-acuminate. 6
5a. Young internodes strongly quadrangular; corolla lobes reflexed at 4/5 the corolla height; free part of filament less than 10 mm long (Borneo) 9. L. lancifolius
5b. Young internodes terete; corolla lobes reflexed at 1/2 to 3/5 the corolla height; free part of the filament more than 10 mm long (Borneo) 3. L. bahajensis
6a. Involucre more than 60 mm long; corolla more than 80 mm long (Malaya, Sumatra, Borneo) 4. L. beccarii
6b. Involucre less than 40 mm long; corolla less than 80 mm long 7
7 a. Involucral bracts broad, spreading after anthesis; flowers in the inflorescence more than 30 (Borneo) 5. L. centiflorus
7b. Involucral bracts narrow, remaining appressed after anthesis; flowers in the inflorescence fewer than 25 8
8a. Anther 1.5-2 mm long, shorter than the free part of the filament (Java) 8. L. gemmiflorus
8b. Anther 4-6 mm long, longer than the free part of the filament (Borneo, Celebes) 2. L. alveolatus

Lepeostegeres (Blume) Blume ex Schult. f. Syst. 7, 2:1611 (Lepeosteog.), 1731 (1830); Miq. Fl. Ind. Bat. 1, 1: 833 (1856); Tiegh. Bull. Soc. bot. Fr. 41: 143 (1894) (Lepost.); Dans. Bull. Jard. hot. Buitenz. 11: 258 (1931); Philipp. J. Sci. 58: 29 (1935); Engl . & Krause, Pfl. Fam.ed. 2 16b: 139 (1935); Loranthus sect. Lepostegeres Blume, Fl. Jav. Loranth. 18 (1829); Elytranthe sect. Lepiostegeres (Blume) Engl . Pfl. Fam. 3, 1:189 (1889); Elytranthe subgen. Palaeoelytranthe sect. Lepiostegeres Engl. Pfl. Fam.Nachtr. 126 (1897). Type Species.-L. gemmiflorus (Blume) Blume.

Stegastrum Tiegh. Bull. Soc. bot. Fr. 42: 447 (1895). Type Species-S. beccarii (King) Tiegh. (lectosyntype). The other three syntypes cited by van Tieghem are S. bahajense (Kiorth.) Tiegh., S. alveolarum Tiegh. and S. lancPfolium Tiegh.

Choristega Tiegh. Compt. rend. 153: 1197 (1911). Type Species. C. alveolata (Tiegh.) Tiegh. (lectosyntype). The other syntype cited by van Tieghem is C. bahajensis (Kiorth.) Tiegh.

Choristegeres Tiegh. Compt. rend. 153: 1197 (1911). Type Species-C. centiflorus (Stapf) Tiegh.

Aerial stem-parasites with runners and opposite penninerved leaves. Inflorescence a pedunculate capitulum with the flowers enclosed in an involucre of 3-12 pairs of decussate imbricate bracts; peduncle dilated at the summit into a flat receptacle bearing 15-50 flowers arranged in decussate sessile dichasia (triads); flowers pedicellate or sessile; bracts other than those of the involucre small and scale-like or absent. Corolla 6-merous, the lobes becoming S-shaped at the point of reflexion before the corolla opens; petals in the open flower usually united almost to the middle. Anthers linear, basifixed, immobile, 4-locular. Style articulate above the base. Basic Chromosome Number.-x = 12.

A genus of about 10 species distributed from the Malay Peninsula to New Guinea, with the greatest concentration of species in the western part of its range. One species is endemic to the area dealt with here.

Lepeostegeres lancifolius. Sarawak, Malaysia. Photo by Yii Puan Ching [S72091]. This species does not occur in New Guinea (here for comparative purposes).

last updated 28 June 2003