Nord. J. Bot. - Section of tropical taxonomy

Indigofera rubromarginata sp. nov. (Leguminosae) from southern Arabia, with a note on I. eremophila

Mats Thulin

Thulin, M. 1995. Indigofera rubromarginata sp. nov. (Leguminosae) from southern Arabia, with a note on I. eremophila. - Nord. J. Bot. 15: 519-521. Copenhagen. ISSN 01 07-055X.

The new species Indigofera rubromarginata, widespread along the coast of southern Arabia in Yemen and Oman, is described and illustrated. The closely related I. eremophila, previously known only from eastern Ethiopia and Somalia, is reported also from Yemen.

M. Thulin, Dept of Systematic Botany, Uppsala University, Villavagen 6, S-752 36 Uppsala, Sweden.

Introduction During field work in southern Yemen in 1992 a small prostrate Indigofera, which could not be identified in the field, was seen several times along the coast. Subsequent studies in the Herbaria of BM, E and K revealed a number of further collections of the same taxon, both from Yemen and Oman, the first made already in 1881. The material has mostly been misidentified as I. argentea Burm. f., a species widespread from northern Africa in the west to India in the east. Apparently no name has previously been given to this southern Arabian plant that is accordingly described below as a new species. Its nearest relative seems to be I. eremophila Thulin, a spe- cies that is here reported from Yemen for the first time.

Indigofera rubromarginata Thulin sp. nov. Type: Thulin, Eriksson, Gifri & Llngstrom 8191, Yemen, Hadramaut, 3 km E of A1 Mukalla, 14"32'N, 49"10'E, 8 Oct 1992 (UPS holotype, Aden Univ., K isotypes).

Species nova ab I. eremophila Thulin habitu prostrato, foliis 5-9-foliolatis foliolis rubromarginatis et floribus minoribus differt. - Fig. 1.

Perennial herb with prostrate radiating stems up to at least

Accepted 2-1-1995 0 NORDIC JOURNAL OF BOTANY

30 crn long from a taproot; stems silvery strigose with hairs closely appressed or sometimes with spreading tips, sometimes with some darker multicellular hairs inter- spersed. Leaves pinnately 5-9-foliolate; rhachis silvery strigose, up to 16 mm long including a petiole of up to 5 mm, prolonged up to c. 1.5 mm beyond lateral leaflets; petiolules c. 0.4 mm long; leaflets obovate to obovate- oblong, 2-6 x 1-3.5 mm, rounded to emarginate at the apex, cuneate at the base, often folded and with a down- curved tip, silvery strigose beneath with appressed or sometimes spreading hairs, more sparsely so and with more slender hairs above; margins usually distinctly red- dish; stipels obsolete, but filiforrn multicellular reddish hairs often present at the insertion of the leaflets; stipules narrowly triangular, up to 1.2 rnm long, usually with reddish multicellular hairs at the margins. Racemes dense, c. 4-10-flowered; rhachis 2-13(-20) mm long, including peduncle of up to 1(-2) mm, zigzag; bracts lanceolate, c. 0.4 mrn long, caducous; pedicels c. 0.8 mm long, erect, spreading or somewhat reflexed in fruit. Ca- lyx c. 2 mm long, divided to about the middle into narrowly triangular lobes, the lowest the longest; the vexillar sinus larger than the others. Corolla red; standard suborbicular, c. 3.5 mrn long, broadly rounded at the apex, very shortly cuneate at the base, white pubescent on the back; wings c. 3.2 x 1.2 mrn, glabrous, shortly clawed; keel c. 3.5 mm long, spurred on each side, not beaked, pubescent near the apex along the lower margin,

Nord. J . Bot. 15 ( 5 ) (1995) 519

with claws c. 1 mm long. Stamens all fertile, c. 2.5 mm long; anthers ovate, c. 0.5 mm long including the c. 0.1 mm long acute apical appendage. Ovary strigulose, lin- ear, several-ovulate; style c. 1-1.2 mm long, upcurved, glabrous; stigma capitate, terminal. Pods ascending, spreading or somewhat reflexed, straight, 7-16 x 1.5-2 mm, subtetragonous, sometimes slightly torulose, stn- gose with appressed to somewhat spreading hairs; endo- carp spotted; seeds 3-6, f square, c. 1.2 mm long, rugose- pitted, pale brown or greenish brown, sometimes mottled with black. - Fig. 1.

Distribution and habitat. I. rubromarginata is fairly widespread and common in the coastal parts of southern Yemen and Oman. The species grows on stony, rocky or sandy ground, often along wadis, on shores, coastal plains and hillsides from sea level up to c. 250 m altitude.

Taxonomic remarks. I. rubromarginata is in the field easily confused with small forms of I. argentea, the two often growing together and having a similar habit. Previ- ously collected material of I. rubromarginata has also in herbaria usually been identified as I. argentea or I . sp. aff. I. argentea. Furthermore, Schweinfurth 175, collected in 1881, was cited as I. burmannii Boiss. (a synonym of I.

argentea, see Gillett 1958: 69) by Schweinfurth (1896: 241) and Schwartz (1939: 104).

However, the reddish margins to the leaflets of I. rubromarginata is a good field character, at least in the populations seen in Yemen. At a closer inspection the usually complete absence of glandular hairs in I. rubro- marginata shows that it is probably not even particularly closely related to I . argentea. Other differences from I. argentea include the short zigzag inflorescences (inflo- rescences more or less straight and usually well above 20 mm long in I. argentea), the spotted endocarp (endocarp non-spotted in I. argentea), the angular rugose-pitted seeds (seeds subglobose and smooth in I. argentea), and the prostrate habit (I. argentea is usually ascending to erect).

The nearest affinities of I. rubromarginata instead seem to be with I. eremophila, a species previously known from eastern Ethiopia and Somalia, but recently found also in Yemen (see below). I. rubromarginata differs from I. eremophila mainly in its prostrate habit (I. eremophila is a more or less erect shrublet), its 5-9- foliolate (not 3-5-foliolate) leaves with reddish margins to the leaflets, and its smaller flowers with stamens c. 2.5 mm (not c. 5 mm) long.

Fig. 1. Indigofera rubromarginata. A: Habit, x 1.4. - B: Calyx, x 1 1 . - C: Standard, x 1 1. - D: Wing, x 1 1. - E: Keel, x 1 1 . - F: Pod, x 5.5. - A, F from Thulin et al. 8191, B-E from Thulin et al. 7860.

520 Nord J. Bot. 15 ( 5 ) (1995)

Collections other than type. Yemen. Abyan: foothills of Jabal alhrays, 21 km E of Shuqrah, 13"24'N, 4So50'E, 29 Sep 1992, Thulin, Eriksson, Gifri & Llngstrom 7860 (K, Aden Univ., UPS). Hadramaut: 1 km above A1 Barah village, 30 km on the pipeline route starting 15 km NE of Riyan, 14"58'N, 49"31'E, 5 Oct 1992, Thulin, Eriksson, Gifri & Lbngstrom 8078A (UPS); Hami, 2 Apr 1881, Schweinfurth 175 (K). Mahrah: 13 km from Sayhut along road to Qishn, 15"1.5'N, 51"20'E, Thulin, Eriks- son, Gifri & Llngstrom 8414 (UPS).

Oman. Dhofar: Wadi Mirbat, 10 Nov 1977, Lawton 1928A (BM, K); 5 km ENE of Mirbat, 17"01'N, 54"44'E, 19 Sep 1984, Miller 6174 (E); Rahah, between Mirbat and Sudah, 16 Sep 1993, Collenette 8805 (E); coast near Sudh, c. 40 km E of Mirbat, 8 Sep 1989, Miller & Nyberg 9188 (E); Khor Gish Gish, E of Sadh, 17"03'N, 5So05'E, 19 Sep 1984, Miller 6190 (E, K, UPS); Wadi Rabkhut, near Hasik, 17"22'N, .55"16'E, 17 Oct 1977, Radcliffe-Smith 5.565 (K); Kuria Muria Is., A1 Hallaniya, 16 Oct 1979, Miller 276.5 (K), 24 Sep 1984, Miller 6352 (E, K, UPS), 14 Jan 1986, A1 Lamki 10 (E); Masirah I., RAF Masirah, 19 Apr 1976, Radcliffe-Smith 4254 (K); ditto, Shi'inzi, 1.5 Apr 1976, Radcliffe-Smith 4214 (K).

Indigofera eremophila Thulin Yemen. Hadramaut: 12 km on road from Riyan to Al Mukalla, 14"35'N, 49"13'E, 3 Oct 1992, Thulin, Eriks- son, Gifri & Lingstrom 8000 (K, UPS); 15 km NE of Riyan, near the pipeline terminal, 14"42'N, 49"29'E, 9 Oct 1992, Thulin, Eriksson, Gifri & Lingstrom 8230 (UPS).

First record for Yemen and Arabia of this species that is widespread in Somalia and also known from eastern

Ethiopia (Thulin 1982, 1989, 1993). The collections in Yemen were made on coastal plains and dunes at 10-40 m altitude. Associated species include Crotalaria aegyp- tiaca, Farsetia longisiliqua, Indigofera argentea, Jatro- pha pelargoniifolia, Pulicaria argyrophylla, Microcharis contorta, Eragrostis rnahrana and Basananthe berbe- roides. Of these species Basananthe berberoides (Pas- sifloraceae) is also a new record for Yemen and Arabia, the species, like I. eremophila, previously being known only from Somalia and eastern Ethiopia (Thulin 1993).

Acknowledgements - The field work in Yemen was supported by a grant from "Regnells botaniska resestipendium". I am indebted to Ms Kerstin Thunberg for the drawing in Fig. 1.

References Gillett, J. B. 1958. Indigofera (Microcharis) in tropical Africa

with the related genera Cyamopsis and Rhynchotropis. - Kew Bull. Add. Series 1.

Schwartz, 0. 1939. Flora des tropischen Arabien. - Mitt. Inst. Allg. Bot. Hamburg 10.

Schweinfurth, G. 1896. Sammlung arabisch-aethiopischer Pflanzen (Fortsetzung). - Bull. Herb. Boiss. 4, App. 2: 115-266.

Thulin, M. 1982. New and noteworthy species of Indigofera (Leguminosae) from NE Africa. - Nord. J. Bot. 2: 41-50.

- 1989. New or noteworthy species of Leguminosae in NE tropical Africa. - Nord. J. Bot. 8: 457-488.

- 1993 (ed.). Flora of Somalia 1. Royal Botanic Gardens, Kew.

Nord. J. Bot. 15 (5) (1995) 52 1