Botanical Journal of the Linnean Society, 2002, 139, 317–322. With 4 figures

INTRODUCTION

The genus Dicoma Cass. (Asteraceae, Mutisieae) con-sists of approximately 50 species of herbs, shrubs and small trees. Most species are from tropical andsouthern Africa and Madagascar, although one speciesoccurs in the Arabian Peninsula and another in Indiaand Pakistan.

Traditionally, this genus has been included in the tribe Mutisieae (Jeffrey, 1967; Cabrera, 1977).Recently, Hansen (1991) has suggested its exclusionfrom this tribe, largely because the surface mor-phology of corolla cells does not show the typicalMutisieae pattern, the corolla is clearly divided into anarrow tube and a broad limb, and in species with bilabiate flowers the inner lips are absent or short and uncoiled. However, recent cladistic analyses of the subfamily Chicorioideare have suggested thatDicoma should be included in the Mutisieae despitethese differences (Karis, Källersjö & Bremer, 1992;Bremer, 1994).

We are currently carrying out a monographic studyof Dicoma (Ortiz & Rodríguez-Oubiña, 1994, 1996;Ortiz, Rodríguez-Oubiña & Tadesse, 1998; Ortiz, 2000;Ortiz & Pulgar, 2000; Ortiz & Coutinho, 2001, etc.)

and related genera of the Mutisieae from tropical andsouthern Africa. In the course of this work we havefound in the material collected by Dinter in Namibiaa new species that we describe herein. Until now thisspecies had been misinterpreted as D. picta (Thunb.)Druce (Merxmüller, 1967).

MATERIAL AND METHODS

This study was based on morphological and anatomi-cal analyses of specimens from the BOL, K, PRE andWIN herbaria (Holmgren, Holmgren & Barnett, 1990).The material was studied with the aid of a dissectingmicroscope. Other micromorphological and anatomicalcharacters were also studied with a compound lightmicroscope. For this part of the study, floral parts werefirst boiled in water and placed in Hoyer’s solution(Anderson, 1954) for observation.

The morphology of the epidermal cell surface of the corolla and corolla twin hairs was classified following Karis et al. (1992), endothecial cell-wallthickening was classified as per Dormer (1962), andtesta morphology was classified according to Grau(1980).

Cypselas of dried material were mounted on alu-minium stubs, and coated with a c. 30 nm layer of goldfor study with a scanning electron microscope (SEM)(LEO 435VP), operating at 15kV.

© 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 139, 317–322 317

A new species of Dicoma Cass. (Asteraceae: Mutisieae)from Namibia

SANTIAGO ORTIZ* and IÑIGO PULGAR

Departamento de Bioloxía Vexetal, Laboratorio de Botánica, Facultade de Farmacia, Universidade deSantiago, 15706 Santiago de Compostela, Galicia-Spain

Received Month 2001; accepted for publication Month 2001

During studies of the genus Dicoma (Asteraceae: Mutisieae), and specifically of the material collected by Dinter inNamibia, we have found a new species named Dicoma obconica. This species has previously been misinterpretedas D. picta (Thunb.) Druce. We present a description with illustrations, and discuss relationships with D. picta andwith D. dinteri S. Moore, the most similar species of the genus. © 2002 The Linnean Society of London, Botani-cal Journal of the Linnean Society, 2002, 139, 317–322.

ADDITIONAL KEYWORDS: Cichorioideae – Compositae – systematics – tropical Africa.

*Corresponding author. E-mail: bvsortiz@usc.es

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Figure 1. Dicoma obconica S. Ortiz sp. nov. A, habit. B, leaf. C, capitulum. D, phyllary. E, disc floret. F, cypsela of discfloret with pappus. G, cypsela of ray floret with pappus. Based on Dinter 8253 (WIN). Dicoma picta (Thunb.) Druce. H,Leaf. I, Capitulum. Based on Acocks 19004 (PRE).

DESCRIPTION

DICOMA OBCONICA S. ORTIZ SP. NOV. (FIG. 1)

Typus: Namibia, Lüderitz South District, 20km northof Witputz to Schwarzkalk, 15.xii.1934, Dinter 8253(Holotypus WIN!; Isotypi BOL!, K!, PRE).

Diagnosis: Speciei Dicoma picta similes, a qua prae-cipue differt foliis quidem linearibus atque dentibusapicem vs. praeditis basi leviter incrassatis, involucroautem obconico atque bracteis multo paucioribus(40–55 non 90–150) efformato, cypselis deniquemaioribus (3.5–4.5mm non 2.5–3mm) pappoque lon-giore (9–11mm non 7.5–8(– 8.5)mm) instructis.

Description: Subshrub. STEM branched; the branches striate, greenish, moderately white-tomentose, with simple hairs and sessile to subsessileglands. LEAVES (1-) 5–15 (–17) ¥ (1-) 1.5–2mm, linearto linear-elliptic, attenuate at base on a decurrent veryinconspicuous pseudopetiole up to 1.5mm long; themargins often serrulate-callose towards the apicalpart; apex mucronate; upper surface greenish,glabrous, with sessile yellowish glands; lower surfacemoderately tomentose with simple hairs and sessileyellowish glands; midrib conspicuous. CAPITULA

numerous per plant, each capitulum solitary on erect-patent bracteate peduncles, 40–65mm long, withoutsubtending leaves; involucre 13–16 ¥ 16–20 (–23)mm,conspicuously obconic, with 40–55 phyllaries arrangedin (5-) 6 (–7) rows, straw-coloured, with a darker stripeon either side of the midrib, gradually narrowing to anacuminate apex, pungent, with simple hairs at lowdensity along the margins and sessile yellowishglands, the margins entire to shortly serrulate princi-pally towards the apical part; with scarious margins,those of the inner phyllaries more conspicuous; phyl-lary sclerenchyma fibres concentrated on the abaxialface; outermost phyllaries 1–2.5 ¥ 1–2mm, deltate toovate-lanceolate, erect-patent, with an acuminate apex0.2–0.5mm long, without scarious margins; middlephyllaries 3–9 (–11) ¥ 1–2mm, lanceolate, erect-patent, with an acuminate apex 1–3mm long, with ascarious margin up to 0.5mm wide; innermost phyl-laries (11-) 12–13 (–14) ¥ (1.7-) 2–2.5mm, longer thanthe outer phyllaries and 2–3mm shorter than thepappus, oblong-lanceolate, erect, with an acuminateapex 2–3mm long; receptacle concave, alveolate, pitssurrounded by a membrane with an irregular dentatemargin 0.3–0.5mm high. Capitula radiate. FLORETS ±20–30 per capitulum. Disc florets bisexual, actin-omorphic, corolla 10–11 ¥ 2–3mm, deeply 5-lobed,white, with subepidermal star-shaped calcium oxalatecrystals, epidermal cell surface ‘intestine-like’ andwith short glandular twin hairs; tube 2.5–6 ¥ 0.5–0.7mm; lobes 4.5–5 ¥ 0.5mm, becoming recurved, with slender submarginal veins. STAMENS exserted

for 1.5–2mm beyond the corolla; filaments 2.3–2.5(–3)mm long, with scarce star-shaped calcium oxalatecrystals; collar 0.4–0.6mm long; anthers 5.5–6mmlong, anther thecae calcarate, endothecial cell wallpolarized (i.e. with thickenings at the extremes); apical appendages c. 1mm long, conspicuously apicu-late; anther tails 1.5–2mm long, with retrorse hairs0.3–0.5mm long and some shorter antrorse hairs at the apex. STYLE 12–13mm long, with star-shapedcalcium oxalate crystals principally towards the

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2

3

Figures 2–3. Disc floret cypsela of Dicoma obconicaS. Ortiz. Fig. 2. SEM micrograph of the surface showingribs and epidermal glands. Scale bar = 500 mm. Fig 3. Light microscope photograph of the mature testa show-ing an epidermal Dicoma type pattern (Grau, 1980) andsubepidermal calcium oxalate crystals orientated in thesame direction. Based on Dinter 8253 (WIN). Scalebar = 50 mm.

base, stylar branches 1.3–1.5mm long, with sweepinghairs forming a subapical ring, covering a surface0.3–0.4mm long, the basal hairs longer than theothers. CYPSELAS 3.5–4.5 ¥ 2–3mm, turbinate, 10-ribbed, hispid, with ascending 0.5–3mm long hairs,inserted between the ribs from the base to the top of the cypsela, with epidermal glands (Fig. 2) andwithout superficial biseriate glands between the ribs,and with abundant star-shaped calcium oxalate crystals in the pericarp; immature testa (subepidermalcalcium oxalate crystals are observed in the immaturetesta, but are subsequently hidden from view by theepidermis of the mature testa) with long-rectangularcrystals orientated in the same direction, mature testaof Dicoma type (Fig. 3); pappus isomorphic, of 130–160barbellate bristles arranged in 3 series, the inner-mostbristles slightly broadened toward base, the longestbristles 9–11mm long, the shortest c. 3mm long; bar-

bellae 0.1–0.2mm long. Corollas of the ray floretsmissing in the material studied. Ray cypselas2–3 ¥ 1mm, obconic, sterile, glabrous or with twinhairs 0.5–2mm long principally at the base; isomorphicpappus of 15–25 bristles, often several of them curved,the longest bristles 10–11mm long, barbellate butalmost ebarbellate at the base (Fig. 1).

DISCUSSION

While Dicoma obconica is easily distinguishable fromother species of the genus, the most morphologicallysimilar species, particularly as regards the presence of ray florets, is probably D. picta, with which it wasconfused by Merxmüller (1967). However, we haveidentified a number of characters, relating to theleaves, involucre, corolla, stamens, cypsela andpappus (Table 1) that allow the two species to be

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Figure 4. Distribution of Dicoma obconica S. Ortiz ( ) and D. picta (Thunb.) Druce ( ).

clearly separated. Furthermore, the location fromwhich the new species was collected is very far fromthe distributional area of D. picta (Fig. 4).

Another species which presents similarities with D.obconica is the likewise Namibian species D. dinteriS. Moore. The latter species has an obconic involucrebut lacks ray florets and shows several other markeddifferences with D. obconica (see Table 1).

ACKNOWLEDGEMENTS

Our thanks go to Manuel Laínz for the Latin diagnosis, to Luis G. Orellana for the illustrations, to Ramiro Barreiro for SEM micrographs, to G.Norman for the English translation, and to thekeepers of the herbaria mentioned for the loan of studymaterial.

REFERENCES

Anderson LE. 1954. Hoyer’s solution as a rapid mountingmedium for bryophytes. Bryologist 57: 242–247.

Bremer K. 1994. Asteraceae. Cladistics and classification.Portland: Timber Press.

Cabrera AL. 1977. Mutisieae – systematic review. In:Heywood VH, Harborne J-B, Turner BL, eds. The biology

and chemistry of the Compositae II. London: Academic Press,1039–1066.

Dormer KJ. 1962. The fibrous layer in the anthers of Compositae. New Phytologist 61: 150–153.

Grau J. 1980. Die Testa der Mutisieae und ihre systema-tische Bedeutung. Mitteilungen (Aus) der BotanischenStaatssammlung München 16: 269–332.

Hansen HV. 1991. Phylogenetics studies in Compositae tribeMutisieae. Opera Botanica 109: 1–50.

Holmgren PK, Holmgren HN, Barnett LC. 1990. IndexHerbariorum. I. The Herbaria of the World, 8th edn. RegnumVegetabile, 120. New York: New York Botanical Garden.

Jeffrey C. 1967. Notes on Compositae. II. The Mutisieae inEast Tropical Africa. Kew Bulletin 21: 177–224.

Karis PO, Källersjö M, Bremer K. 1992. Phylogeneticanalysis of the Cichorioideae (Asteraceae), with emphasis on the Mutisieae. Annals of the Missouri Botanical Garden79: 416–427.

Merxmüller H. 1967. Prodromus einer Flora von Südwest-africa, Fam. 139, Asteraceae. Lehre: J. Cramer.

Ortiz S. 2000. A phylogenetic analysis of Dicoma Cass. &related genera (Asteraceae: Cichorioideae: Mutisieae) basedon morphological and anatomic characters. Annals of theMissouri Botanical Garden 87: 459–481.

Ortiz S, Coutinho AP. 2001. Achyrothalamus reduced to Erythrocephalum (Asteraceae: Mutisieae). Taxon 50: 389–403.

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Table 1. Principal morphological differences between Dicoma obconica, D. picta and D. dinteri

Character D. obconica D. picta D. dinteri

Leaf shape Linear to linear-elliptic Oblanceolate to spathulate Linear-elliptic to linear-oblanceolate

Involucre shape Obconic Campanulate ObconicInvolucre size 13–16 ¥ 16–20 (–23) 8–15 (–18) ¥ 15–25 9–12 ¥ 13–15Number of phyllary rows per (5–) 6 (–7) 7–8 (–9) 4–5

involucreNumber of phyllaries per 40–55 90–150 30–50

involucrePhyllary shape Gradually narrowed at Gradually narrowed at Abruptly narrowed at the

the apex the apex apex in a apical awnLength of the innermost (11-) 12–13 (–14) 13–17 8–10

phyllaries (mm)Phyllary indumentum Glabrescent Glabrous to glabrescent Often densely white-

tomentoseRay florets Present Present AbsentInvolucre/disc floret pappus Involucre 2–3mm Involucre up to 3mm Involucre 0–2mm shorter

length relation shorter than the pappus longer than the pappus than the pappusDisc floret anther length (mm) 5.5–6 6–7 5.5–6Disc floret corolla length (mm) 10–11 8–10 8–9Disc floret cypsela size (mm) 3.5–4.5 ¥ 2–3 2.5–3 ¥ 1.5–2 2–2.5 ¥ 1.2–1.5Disc floret pappus length (mm) 9–11 7.5–8 (–8.5) 7–8Number of bristles per pappus 130–160 100–130 130–160

of the disc florets

Ortiz S, Pulgar I. 2000. A new species of Dicoma (Asteraceae:Mutisieae) from Swaziland. Nordic Journal of Botany 20:347–352.

Ortiz S, Rodríguez-Oubiña J. 1994. Dicoma paivae andDicoma cinerea (Asteraceae), two new species from Somalia.Canadian Journal of Botany 72: 1478–1481.

Ortiz S, Rodríguez-Oubiña J. 1996. Two new species of

Dicoma Cass. (Asteraceae) from Somalia and Ethiopia.Nordic Journal of Botany 16: 277–281.

Ortiz S, Rodríguez-Oubiña J, Tadesse M. 1998. Ataxonomic revision of Dicoma (Asteraceae: Cichorioideae:Mutisieae) for the Horn of Africa. Annals of the MissouriBotanical Garden 85: 440–459.

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