Socratina phillipsoniana Callm. & Luino

Callmander, M. W., I. Luino, S. Da-Giau, C. Rakotovao & L. Gautier, 2014, A synoptic revision of the Malagasy endemic genus Socratina Balle (Loranthaceae)., Candollea 69 (1), pp. 65-73 : 68-72

Socratina phillipsoniana Callm. & Luino , spec. nova ( Fig. 2 , 3 , 4 ).

Typus: MADAGASCAR. Prov. Mahajanga: Beanka, partie N, 18°07’05”S 44°27’04”E, 174 m, 23.VII.2013, fl. & fr., Luino & Ranaivoarisoa 63 (holo-: G [ G00341307 ]!; iso-: K [ K000865017] !, MO!, P [ P00853035 ]!, TEF!).

Haec species a congeneris foliis glabrescentibus, alabastro apice fusiformi atque corolla extus secus quamque suturam loborum conspicue longitudinaliter fimbriata trichomatibus villosis dendriticis longis praeut indumento floccoso breviore corollam extus ceterum obtegente distinguitur.

Hemi-parasitic shrub, 0.5-1 m in diam., young fertile and sterile parts covered by a white floccose indument; twigs c. 0- 7- 1 mm long. Leaves alternate on young shoots, becoming clustered on twigs; petiole 1-6 mm, sometimes sub-sessile; lamina papery-coriaceous, obovate to oblanceolate, rounded at apex, cuneate or attenuate at base; (10-)15-25(-45) X 10- 15 (-20) mm, tomentose at first, soon becoming glabrescent, triplinerved, attenuate at the base. Inflorescence an umbel, developing at nodes, sessile, 2-5-flowered. Bracts c. 2.5 mm long, boat-shaped, apex rounded, soon glabrescent except for margins and apex that remain covered with longer reddish brown persistent trichomes. Receptacle c. 3 X 2 mm, covered with a dense white indument. Calyx short, c. 1 mm long, green, soon glabrescent, with 5 scarcely differentiated teeth. Corolla 5-merous, 35-50 mm long; the outer surface covered with a dense white shorter floccose indument, composed of dendritic trichomes up to 0.8 mm long, the ramifications forming a series of closely whorled layers; and with a conspicuous longitudinal villous fringe along each suture, composed of slender elongated dendritic trichomes up to 1.5 mm long with a few irregular proximal ramifications and only a few distal whorled ones. Buds sub-conic, with a fusiform apex in the upper 1/3 distal part; tube splitting unilaterally between 2 lobes at anthesis, sometimes slightly splitting between the other lobes distally; lobes c. 20 X 1.5 mm, broadly linear-spatulate in the proximal part, apiculate in the last 7-10 mm distal part. Stamens coiled, arising at or just above the base of the corolla lobes; anthers 2.5 mm long, rolled; filaments 4 mm long, puberulent, dark purple. Style 40 mm in length, pale green, covered with long white trichomes except in the distal 4 mm, filiform. Stigma obovoid to globular, c. 0.5 mm in diam. Fruit a red berry “in vivo”, pale orange when dried, covered with a sparse indument, obovoid, c. 12-14 X 7-9 mm.

Etymology. – The species is named in honour of our colleague Peter Phillipson who obtained funds and arranged the first field mission to Beanka in 2009 and contributed to the floristic checklist recently published on the region ( GAUTIER & al., 2013). Peter has collected over 3000 plants in Madagascar, especially in the dry south-western region where he first collected in 1987. He has a wide knowledge on many plant groups on the Island and participates actively in the milestone “Catalogue of the Vascular plants of Madagascar ” project ( MADAGASCAR CATALOGUE, 2014).

Distribution and ecology. – Socratina phillipsoniana is only known from the limestone region of Bemaraha and Beanka in western Madagascar ( Fig. 1 ).

Conservation status. – With an EOO of 557 km ², and an AOO of 27 km ² and three subpopulations, one of which occurring in the protected area network (Bemaraha) and the other two in a projected protected area and already holding a temporary status (Beanka), S. phillipsoniana is assigned a preliminary status of Vulnerable (VU D2) following IUCN Red List Categories and Criteria ( IUCN, 2012).

Notes. – Socratina phillipsoniana is similar to S. bemarivensis in having a corolla tube splitting unilaterally at anthesis. It can however easily be recognized when flowering by the conspicuous longitudinal villous fringe of long dendritic trichomes on the outer surface of its corolla along each suture in addition to a uniform floccose indument over the entire surface (vs. uniform indument in S. bemarivensis ) and the fusiform shape of the bud apex (vs. rounded in S. bemarivensis ) ( Fig. 3 , 4 ). When sterile S. phillipsoniana differs from S. bemarivensis by its glabrescent leaves whereas the latter species has leaves covered by a russet indumentum ( Fig. 2 ).

Paratypi. – MADAGASCAR. Prov. Mahajanga: Beanka, partie S, Andoloposa, 18°00’27”S 44°30’10”E, 287 m, 20.III.2012, fr., Hanitrarivo, Bolliger & Rakotozafy 343 ( BR, G [ G00376797 ], K, MO, P, TEF); Tsingy de Bemaraha, S of the river Manambolo , 19°09’S 44°49’E, 50 m, 15.XII.1996, Jongkind, Andriantiana & Razanatsoa 3548 ( G [ G 00404128], P [ P05096712 ], MO, WAG); Beanka, partie N , 18°07’09”S 44°27’02”E, 165 m, 23.VII.2013, fl. & fr., Luino & Ranaivoarisoa 60 ( BR, G [ G00341313 ], K, MO, P, TEF).

Figures

Fig. 1. – Map showing the distribution of Socratina bemarivensis (Lecomte) Balle (stars), S. keraudreniana Balle (squares) and S. phillipsoniana Callm. & Luino (circles) in Madagascar, plotted on the map of phytogeographical domains sensu HUMBERT (1955).

Fig. 2. – Living plants. A. Socratina keraudreniana Balle; B. S. bemarivensis (Lecomte) Balle; C. S. phillipsoniana Callm. & Luino. [Photos: A: J. Bosser; B: F. Ratovoson; C: I. Luino]

Fig. 3. – Socratina phillipsoniana Callm. & Luino. A. Fertile branch with flowers and fruit; B. pex of open flower; C. Bud apex showing the fringe of trichomes along the sutures; D. Calyx and bract. [Luino & Ranaivoarisoa 63, G] [Drawings: S. Da-Giau]

Fig. 4. – Trichomes. A-D: Socratina phillipsoniana Callm. & Luino; E-G: S. bemarivensis (Lecomte) Balle; H-J: S. keraudreniana Balle. A, E, H. Trichomes from the outer surface of the corolla tube: side view; B, F, I. Trichomes from the outer surface of the corolla tube: cross section; C, G, J. Trichome from the inner surface of the corolla tube: side view; D: Trichome from villous fringe of the corolla tube: side view. [A-D: Luino & Ranaivoarisoa 63, G; E-G: Ratovoson 105, P; H-K: Rakotomalaza & Messmer 1816, G] [Drawings: S. Da-Giau]