Botanical Journal of the Linnean Sociely (1988), 96: 323-332. With 2 figures

The tribal position of Oedera L. (Compositae)

ARNE A. ANDERBERG AND MAR1 KALLERSJO

Swedish Museum of flatural History, Department of Phanerogamic Botany, P . 0. Box 50007, S-I04 05 Stockholm, Sweden

Received December 1986, accepted f o r publication February I987

ANDERBERG, A. A. & KALLERSJC), M., 1988. The tribal position of Oedera L. (Compositae). The South African genus Oederu L. (Compositae-Anthemideae) is shown to be closely related to the South African genera Relhania and Ltyyseru. A transfer of Oedera from the tribe Anthemideae to the tribe Inuleae is proposed. Several synapomorphies, like a two-layered sexine, concave leaves, pappus of connate scales, long and slender cypselas define the monophyletic group. The pollen-wall morphology of Oedera is described and the chromosome number 2n = 14 is reported.

ADDITIONAL KEY WORDS:-Anthemideae - Eroedu - Inuleae - Leyseru - Relhania

CONTENTS

Introduction . . . . . . . . . . . . . . . . . . . 323 Historical outline . . . . . . . . . . . . . . . . . . 324 Comparative morphology . . . . . . . . . . . . . . . . 324

Habit. . . . . . . . . . . . . . . . . . . . 324 Leaves . . . . . . . . . . . . . . . . . . . 325 Organization of the synflorescence . . . . . . . . . . . . . 325 Capituh . . . . . . . . . . . . . . . . . . . 325 Involucre . . . . . . . . . . . . . . . . . . . 325 Receptacle 327 Ray-florets . . . . . . . . . . . . . . . . . . 327 Disc-florets . . . . . . . . . . . . . . . . . . 327 Pollen . . . . . . . . . . . . . . . . . . . 328

Cytology . . . . . . . . . . . . . . . . . . . . 329 Phytochemisrry . . . . . . . . . . . . . . . . . . 329 Discussion. . . . . . . . . . . . . . . . . . . . 329 Acknowledgements . . . . . . . . . . . . . . . . . 331 References. . . . . . . . . . . . . . . . . . . . 33 1

. . . . . . . . . . . . . . . . . .

INTRODUCTION

The genus Oedera comprises six species (Bond & Goldblatt, 1984) confined to the Cape Province of South Africa. The genus is easily recognized by its small capitula which are congested into dense secondary heads, surrounded by leaves. Oedera is traditionally considered to be a member of the tribe Anthemideae, mainly because of its truncate and apically penicillate style-branches, its indistinct anther tails, and its lack of capillary pappus bristles.

0 1988 The Linnean Society of London 323

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l\'hile analysing character distributions in the Anthemideae and the Inuleae, lie came to realize that there was a close resemblance between Oedera and the tivo genera Relhania L'Hkrit. (29 species), and Leysera L. (four species), of the Inuleae. The question arose whether Oedera should be included in the Inuleae, o r if Relhnnia and Ltysern should be transferred to the Anthemideae. For this investigation herbarium material of the genera Relhania, Leysera, and Oedera, in the Swedish Xfuseum of Xatural History, Stockholm (S) has been examined. In addition to macro-morphological characters, the structure of the pollen-walls provided information concerning the relationship of Oedera.

\Se argue that Oedera is better treated as a member of the Inuleae Athrixiinae, closely related to Relhania and Leysera, than as a genus of the Anthemideae.

HIS I ORIC'AL Or 1 L I h E

Oedeia 1% as described by Linnaeus in the .2lantissa planlarum (1 771). Cassini 1825 I . the founder of the Compositae tribal classification, placed Oedera near

the genera Disparago and E&opappus in the Inuleae-Gnaphaliinae. Cacsini was not followed by later authors such as Lessing (1832), who treated

Oedera as a genus of the Anthemideae. De Candolle (1838) retained Oedera in the .lnthemideae. As a curiosity it can be mentioned that Oedera speczosa and Oedera qbirulata. cited by De Candolle, are synonymous with two species of Relhania

I R. speczosa and R. calq'cznaj, according to Bremer (1976). Harvey, in Flora Capenszs ( 1865), grouped Oedera together with several

unrelated genera in what he called the subtribe Helenieae of the tribe Senecionideae. However, his definition is not comparable with the modern circumscription of the tribe Helenieae.

In the systems of Bentham (1873), Hoffmann (1891), and of modern taxonomic workers, for example Dyer (1975) and Heywood & Humphries 1977 , Oedera is reinstated in the Anthemideae.

Linnaeus' Oedera is antedated 3 years by the older homonym Oedera Crantz = Liliaceaei. This \+as first pointed out by Mansfeld (1935: 441) who explicitly

stated that unless Oedera L. was conserved, a new generic name must be found tbr the taxon. The contribution of Mansfeld was part of a major proposal to conserve se\ era1 later homonyms. Later the same year, Mansfeld's proposal to conserve Oedera L. against Oedera Crantz was accepted by a decision of the Botanical Congress in Amsterdam (Camp, Rickett & Weatherby, 1947).

LevJns 11948) was apparently unaware of the fact that Oedera had been conserced when she, citing Llansfeld (1935), introduced the anagram Eroeda as d substitute name for Oedern L. Consequently, the generic name and the new combinations proposed by Levyns are all superfluous. Bond & Goldblatt (1984) use the name Oedera, but unfortunately Levyns' names are often used in herbaria.

CO1lPARA?'I\ E LIORPHOLOGY

Habit

All species of Oedera have a shrubby, ericoid habit, just like most species of Rdhania. In the group of genera to which Relhania and Leysera belong, shrubs are

THE TRIBAL POSITION OF OEDERA L. 325

predominant and herbs are rare. For convenience the genera Relhania, Leysera, Rosenia, Oreoleysera, Antithrixia, Metalasia, Bryomorphe, Stoebe, Lachnospermum, Pterothrix, Disparago and Elytropappus will be called the Relhania group in the following text.

Leaves

The members of the Relhania group all have entire, often xeromorphic leaves which are generally involute to concave or channeled, with a white-tomentose upper surface. This rare leaf-type has been used as an important character for delimiting the Relhania group of genera from other Inuleae-Athrixiinae (Bremer, 1976). The leaves in Oedera are xeromorphic, entire, and devoid of white tomentum on the upper leaf surface, but they are often distinctly concave, like in many Relhania species where the tomentum of the upper surface of the leaves has been reduced (Bremer, 1976).

Oedera and Leysera both have tubercle-like trichomes, scattered on the surface and along the margin of the leaves. In spite of the fact that the leaves are entire, the presence of marginal trichomes makes the leaves of some Oedera species seem serrulate or denticulate.

Organization of the synjorescence

The species of Leysera all have single capitula on long peduncles (Fig. 1D). Relhania has the heads arranged in many different ways, from shortly pedunculate, solitary capitula (e.g. R. s-eciosa), laxly corymbose capitula (e.g. R. biennis, Fig. lC) , to congested, sessile capitula (e.g. R. steyniae, Fig. 1B) subtended by the upper leaves. In Oedera the salient feature is the presence of densely congested capitula arranged into secondary heads, which are surrounded by large leaves (Fig. 1A). When scrutinized these secondary heads of Oedera, and the congested capitula of some Relhania species, do not differ in any significant way.

Capitula

The capitula of Relhania and Leysera are all radiate, or rarely disciform, and radially symmetrical even in densely congested synflorescences. The capitula of Oedera, on the other hand, are radiate peripherally, but disciform towards the centre of the secondary head. Most capitula are radially symmetrical and have mini-ligulate or even tubular female florets. However, the outer capitula are asymmetrical due to the well-developed lamina of the ray-florets situated at the margin of the secondary head. In this way the secondary head in Oedera very much resembles one large radiate capitulum.

Involucre

The involucral bracts of Oedera, Relhania, and Leysera always have a basal sclerenchymatous portion and an apical scarious lamina. In Oedera the capitula, and also the involucral bracts, are concealed by the leafy involucre surrounding the secondary head. In some Relhania species (e.g. R. steyniae) a similar feature

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THE TRIBAL POSITION OF OEDERA L. 327

can be seen (Fig. 1B). Scarious involucral bracts are characteristic of many Inuleae-Athrixiinae and most Inuleae-Gnaphaliinae as well as of the Anthemideae in general.

Receptacle

Chaffy receptacles are found in Oedera and in most species of Relhania. Receptacular, scale-like projections (sensu Bremer, 1978) occur in Leysera. The other genera of the Relhunia group are generally epaleate.

Ray-jorets

The ray-florets in Relhania, Leysera, and Oedera are strikingly similar (Fig. 1 E-H) . They are female and have the same shape, although the lamina in the ray-florets of Oedera are larger than in most Relhania and Leysera species.

The lamina is bright yellow but often has a longitudinal, broad, purple band dorsally. In Oedera only the outermost female florets have a well-developed lamina, while most female florets have a reduced lamina, being mini-ligulate or tubular (see also above under capitula). Like the members of the Inuleae (Baagoe, 1978), the epidermis of the lamina in Oedera is of the Senecionoid type (according to Baagoe, personal communication), This separates the genus from the Anthemideae which has the Helianthoid type (Baagoe, 1977). Judging from light-microscopical studies, it seems probable that the ray-floret laminas in Relhania and Leysera also have an epidermis of the Senecionoid type.

The tube of the ray-florets in several Relhania species, and almost all Lgsera and Oedera species, have rather large, conical, multi-cellular trichomes. These consist of two irregular rows of rather thick-walled, bulging cells which give the trichome a very characteristic shape (Fig. 1U-W). In some Relhania species (e.g. R. cabcina), the trichomes end with a few, minute glandular cells. In other species of Relhania different types of glandular trichomes may occur.

The style-branches have two apically somewhat confluent stigmatic lines, ending just below a small apical tuft of blunt sweeping-hairs. The orientation of the style-branches (Robinson, 1984) is radial in Oedera and in Relhania and Leysera. The style-base is somewhat bulb-shaped.

The cypselas are thin-walled, terete to slightly angled and conspicuously long and slender in all three genera. Oedera has glabrous fruits, while in Relhania and Leysera the cypselas are either glabrous or hairy in different species. The pappus consists of either free or connate scales only.

Disc-Jorets

In all three genera, the disc-florets are short-lobed, yellow, and rather distinctly differentiated into a long, cylindrical limb and a long narrow tube. The veins of the corolla are always well developed along the margins of the corolla-lobes. The tube is often beset with the same kind of large, bulging, conical trichomes as those occurring in the ray-florets.

The style (Fig. 11-L) has fully separated stigmatic lines in all three genera, but some variation in the arrangement of the sweeping hairs can be seen. Most

328 A 4 AhDERBERG A S D 51 LALLERSJO

species ha\ e apically penicillate styles, although several Relhanza species have sweeping-hairs down to about half the length of the style-branches. A similar tendenc) can be seen in Oedera. The bulb-shaped style-base is attached to a short ctylopodium in all genera.

The anther thecae (Fig. la-T) are distinctly tailed at the base in Relhania and Lu_ysera 'Fig. 1R-T). The anthers of Oedera (Fig. I Q ) have inconspicuous tails. which are easily overlooked. The endothecial tissue is polarized (Dormer, 1962 in virtuall) all genera of the Inuleae-Gnaphaliinae and the Inuleae-Athrixiinae, including the Relhania group. Oedera also has polarized endothecial tissue, while the prevailing condition in the Anthemideae is radial cndothecial tissue.

The cypselas are similar to those of the ray-florets. In species with hairy fruits, the disc-floret cy pselas are significantly less hairy compared to those of the ray- floret$. The pappus is similar to that of the ray-florets, except in Leysera where fit e apicall! plumose bristles accompan) the scales.

Pollen

'The pollen morphology of Relhanza and Leysera has been described by Besold 197 1 1 . Like other Inuleae-Gnaphaliinae and Inuleae-Athrixiinae the sexine is

two-layered with a baculate outer layer and an irregularly interlaced inner 1a)er. This has been called the Inuloid pollen type by Skvarla et al . (1977) who interpreted the inner layer as the extremely ramifying bases of the bacula. Our intestigation of the pollen morphology in Oedera (Fig. 2B) reveals the same kind of tuo-la)ered sexine as in Relhania (Fig. 2A). Oedera, just like the genera of the Relhanza group, has caveate pollen with bacula perforated by internal foramina. 'These two characters occur in many tribes of the Compositae but not in the 'Qnthemideae.

Figure 2. Pollen walls of Relhanta .r@niae !.I,, and Oedern inlermedia (B) showing double srxine with a haculatr outer. and an irregularly perforated inner layer. Scale bars = 2 pm. A: Bremer 223 (S). B: Kallcr\.io 121 S ' .

THE TRIBAL POSITION OF OEDERA L.

CYTOLOGY

329

The predominant basic chromosome number in the Inuleae-Athrixiinae and the Inuleae-Gnaphaliinae is equal to, or a multiple of n = 7 , which is rare in the family. The chromosome number in Relhania is 2n = 14, except in the annual species which have 2n = 10 (Bremer, 1976). In Leysera 2n = 8 (Bremer, 1978), and 2n = 14 (Humphries, Murray, Bocquet & Vasudevan, 1978) has been reported.

Seeds of Oedera intermedia, collected by Kallersjo in the field, have been grown in the greenhouses of the Department of Botany, Univerity of Stockholm. Root- tips were pre-treated in a 0.4% colchicine solution, fixed in Carnoy’s (99% ethanol : glacial acetic acid, 3 : l ) , squashed and stained in aceto-orcein. The chromosome number proved to be 2n = 14.

PHYTOCHEMISTRY

The presence of the polyacetylene pentaynene and of benzofurans are a common feature in many tribes of the Compositae, including the Inuleae, but are lacking in for example the Anthemideae (Srarensen, 1977; Proksch & Rodriguez, 1983). Bohlmann & Zdero (1972) reported pentaynene and a benzofuran derivative from Leysera. Bohlmann & Suwita (1978) demonstrated a benzofuran in Relhania. Only open-chained, biogenetic precursors of benzofurans have been found in the Anthemideae (Proksch, 1985). On the chemical constituents of Oedera, nothing has to our knowledge been published.

DISCUSSION

The main reason for the traditional systematic position of Oedera in the Anthemideae is the combination of the characters untailed anthers, truncate and apically penicillate style-branches, and lack of capillary pappus bristles. However, these characters are no criteria for maintaining its tribal position.

Although short and inconspicuous, anther tails do actually occur in Oedera. This character state agrees with our notion that Oedera could be transferred to the Inuleae. The presence of tailed anthers alone is not an argument for excluding Oedera from the Anthemideae, since some genera of that tribe have tailed anthers (e.g. Osmitopsis Cass. and Inulanthera Kallersjo) .

The truncate and apically penicillate style-branches of the Anthemideae and of Oedera are essentially of the same type as the styles of the Inuleae-Athrixiinae and the Inuleae-Gnaphaliinae. Thus, the style character alone does not indicate a position of Oedera within the Anthemideae.

The lack of capillary pappus bristles, often used as one of the key-characters of the Anthemideae, is frequently seen also in the Inuleae (e.g. Asteriscus, Relhania) . The pappus scales in Oedera are indistinguishable from the scales ocurring in Relhania.

None of the characters that have been used to classify Oedera together with the Anthemideae proper are unique synapomorphies, uniting these two groups only. Furthermore, the presence of polarized endothecial tissue in the anthers, Senecionoid ligule epidermis, caveate pollen, and well-developed veins in the disc-floret corollas, contribute to make Oedera anomalous in the tribe Anthemideae.

330 r\ ANDERBERG AND &I KALLERSJo

A two-layered sexine of the pollen wall is rarely found in the Compositae, and Mas called the Inuloid type by Skvarla, Turner, Pate1 & Tomb (1977). The Inuleae-Athrixiinae and the Inuleae-Gnaphaliinae are the groups that are defined b) Inuloid pollen-walls. Thus being an apomorphy, the presence of the Inuloid pollen-wall in Oedera presents a strong argument for transferring Oedera to the Inuleae-Athrixiinae.

The peculiar trichomes on the corolla tubes, the long and slender cypselas with a pappus of scales, and the concave leaves are synapomorphies combining Oedera with the genera Relhania and Leyrera of the Inuleae-Athrixiinae. Possibly, the presence of paleae in Reihania and Oedera could be a synapomorphy for these two genera. The traditional view has been to regard absence of paleae as an apomorphic character state. Due to the wide distribution of both paleate and epaleate receptacles in most tribes of the Compositae, it is vitually impossible to make a generally valid polarization of the two character states. Thus, in the epaleate Relhanza-group of the generally epaleate Inuleae, chaffy receptacles are more parsimoniously interpreted as apomorphic.

'l'he shrubb) habit, the congested capitula, the involucral bracts with a sclerench) matous basal portion and a scarious lamina, the purple dorsal band of the ray-floret lamina, and the shape of the disc-florets, are all character states that are ver) similar in Oedera and in the Reihania group. Each contributes to the notion that Oedera and the Relhanza group belong to the same monophyletic group within the Inuleae-Athrixiinae.

The radiall) orientated style-branches of the ray-floret style, occurring in Oedrra and Relhanza, is a rare feature in the Inuleae, where the styles of the ray- florets are generally tangentially orientated. This character is poorly known except from a few representatives from each tribe which were examined by Robinson 19841. t\ccording to Robinson, radially orientated style-branches of the ray-florets are known only in the Anthemideae, Astereae, Senecioneae, and in the Heliantheae.

The chemical compounds of Leysera and Reihania, mentioned above, are nbwnt from the Anthemideae. It seems reasonable to state that the Anthemideae are defined by a reduction of the biosynthetic pathways leading to production of pentaynene and benzofurans. If presence of these compounds are conGdered to be plesiomorphies, the) tell us that the Relhania group cannot be included in the Anthemideae without severely weakening the definition of that tribe. Even if the opposite is advocated, the Relhania group would still not fit in the Anthemideae, since it would be linked to other Inuleae by the presence of pentaynene and benzofurans.

Considering the number of apomorphies combining Oedera, Relhania and Lcysera into a monophyletic group, it is not surprising to find the unusual chromosome number 2n = 14 also in Oedera.

A comtnon anccstr) can be hypothesized for the genera of the Relhania group dnd Oedera. For the reasons presented above, the Relhanza group cannot be transferred to the Anthemideae without bringing about a weaker definition of that tribe. Thus Oedera must be transferred to the Inuleae.

The phylogeny of the genera Relhanza, Leysera, Oedera and other members of the monophyletic Relhania group cannot be solved at this stage but will be treated more thoroughly in a generic monograph of the Inuleae at present in preparation.

THE TRIBAL POSITION OF O E D E R A L. 33 1

ACKNOWLEDGEMENTS

We would like to express our gratitude to Dr K. Bremer, Swedish Museum of Natural History, Stockholm, for valuable discussions on character distribution in the Anthemideae, and to him and Professor B. Nordenstam, Swedish Museum of Natural History, Stockholm, for their useful comments on an earlier draft of the manuscript.

Our thanks are also due to Dr S. Nilsson and Ms E. Grafstrom of the Palynological Laboratory, Swedish Museum of Natural History, Stockholm, who at our request kindly helped us with preparation of pollen grains and TEM-photography.

We are also grateful to Mr P. Litfors for nursing the seedlings of Oedera. Financial support has kindly been provided by the Swedish Natural Science

Research Council NFR Grant 240 1 - 108 for Compositae taxonomy.

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