Ulrich Meve

Floral biology and pollination in stapeliads — new results and a literature review

The myiophilous pollination syndrome of stapeliads is investigated. Olfactory stimuli, imitating dung or decaying organic (zoogenic or phytogenic) matter, are used as attractants, together with mimetic colouration and, sometimes mimetic sculpturing. In most species nectar is present. The nectar mainly serves as optical attractant causing brilliance effects, and as visitor guide. However, nectar obviously is also a reward in many species. Flies (Cyclorrhapha:Calyptratae) constitute the most important pollinating group. In the pollination process they carry pollinaria only at the distal parts of their proboscis, never on their legs. No fundamental differences between the pollinator spectra of flowers in habitat and cultivated ones were observed.

A molecular phylogeny and generic rearrangement of the stapelioid Ceropegieae (Apocynaceae-Asclepiadoideae)

Abstract. Representatives of nearly all genera of the taxon-rich stem-succulent stapeliads and most of the few related, leafy genera were analyzed. Sequence data from two non-coding molecular markers (ITS region of nrDNA and trnT-L and trnL-F spacers as well as the trnL intron of cpDNA) support the traditional tribal affiliation of the genera, which form a monophyletic group. This monophylum breaks into a basal Neoschumannia/Anisotoma/Riocreuxia/Sisyranthus nk;clade, from which the core Ceropegieae are derived. The four Ceropegia species included are not monophyletic, and their relationship to Brachystelma changes depending on the marker studied. The stem succulent taxa fall in a number of well supported, but unresolved clades, the most prominent being the predominantly southern African clade comprising Orbea, Stapelia and some other genera. The most derived taxa of NE Africa, Duvaliandra and White-sloanea, are basal to this southern African clade. The other clades comprise the more basal genera of stem-succulent stapeliads, including the members of the Caralluma complex. Of the 17 genera accepted by Plowes for the Caralluma complex, seven are recognized: Caralluma, Apteranthes, Australluma, Boucerosia, Caudanthera, Desmidorchis and Monolluma. New combinations are proposed in 15 cases; Caralluma adscendens var. geniculata is raised to specific rank. Anomalluma is reinstated, and Pseudolithos mccoyi is transfered to it. A broadened concept for Orbea (incl. Angolluma and Orbeopsis) is recognized, but Orbeanthus is kept separate. The monotypic Ballyanthus, recently separated from Orbea, is nested within Duvalia. Piaranthus (incl. Huerniopsis) is monophyletic. The bitypic Notechidnopsis is reduced to the type species, N. tessellata, while N. columnaris is transferred to a new genus, Richtersveldia.

Fly pollination in Ceropegia (Apocynaceae: Asclepiadoideae): biogeographic and phylogenetic perspectives

BACKGROUND AND AIMS Ceropegia (Apocynaceae subfamily Asclepiadoideae) is a large, Old World genus of >180 species, all of which possess distinctive flask-shaped flowers that temporarily trap pollinators. The taxonomic diversity of pollinators, biogeographic and phylogenetic patterns of pollinator exploitation, and the level of specificity of interactions were assessed in order to begin to understand the role of pollinators in promoting diversification within the genus. METHODS Flower visitor and pollinator data for approx. 60 Ceropegia taxa were analysed with reference to the main centres of diversity of the genus and to a cpDNA-nrDNA molecular phylogeny of the genus. KEY RESULTS Ceropegia spp. interact with flower-visiting Diptera from at least 26 genera in 20 families, of which 11 genera and 11 families are pollinators. Size range of flies was 0.5-4.0 mm and approx. 94 % were females. Ceropegia from particular regions do not use specific fly genera or families, though Arabian Peninsula species are pollinated by a wider range of Diptera families than those in other regions. The basal-most clade interacts with the highest diversity of Diptera families and genera, largely due to one hyper-generalist taxon, C. aristolochioides subsp. deflersiana. Species in the more-derived clades interact with a smaller diversity of Diptera. Approximately 60 % of taxa are so far recorded as interacting with only a single genus of pollinators, the remaining 40 % being less conservative in their interactions. Ceropegia spp. can therefore be ecological specialists or generalists. CONCLUSIONS The genus Ceropegia has largely radiated without evolutionary shifts in pollinator functional specialization, maintaining its interactions with small Diptera. Intriguing biogeographic and phylogenetic patterns may reflect processes of regional dispersal, diversification and subsequent specialization onto a narrower range of pollinators, though some of the findings may be caused by inconsistent sampling. Comparisons are made with other plant genera in the Aristolochiaceae and Araceae that have evolved flask-shaped flowers that trap female flies seeking oviposition sites.

Advances in apocynaceae : The enlightenment, an introduction

Abstract This issue of the Annals of the Missouri Botanical Garden is devoted to advances in the Apocynaceae s.l. and is based on the symposium, “Recent Progress in the Systematics of Apocynaceae,” held at the XVII International Botanical Congress in Vienna in 2005. The collection of papers presented here spans the phylogenetic and geographic breadth of the family and includes at least one study focused on representatives from each of the five subfamilies: Rauvolfioideae, Apocynoideae, Periplocoideae, Secamonoideae, and Asclepiadoideae. The papers range from higher-level phylogenetic analyses to more narrowly defined case studies and include new results in phylogenetics, taxonomy, biogeography, pollination biology, and a pharmacophagous plant–butterfly interaction involving pyrrolizidine alkaloids, as well as a new hypothesis for the evolution of pollinia and loss of a compitum in some advanced taxa. An updated classification scheme of the Apocynaceae is presented, with one additional tribe recognized in Rauvolfioideae (the Aspidospermeae) and three in Apocynoideae (the Nerieae and Odontadenieae as well as the Baisseeae, which are elevated in rank here). In Asclepiadoideae, seven subtribes are recognized within Asclepiadeae (the Asclepiadinae, Cynanchinae, Tylophorinae, Metastelmatinae, Orthosiinae, Oxypetalinae, and Gonolobinae) and four within Ceropegieae (the Anisotominae, Leptadeniinae, Heterostemminae, and Stapeliinae). Taken together, the papers here present the most up-to-date overview of the family available at this time.

Subtribal division of Ceropegieae (Apocynaceae-Asclepiadoideae)

Monophyly and sister group relationship of Ceropegieae and Marsdenieae, the two Asclepiadoideae tribes possessing erect pollinia, are confirmed by molecular investigation of non-coding cpDNA markers (trnT-L and trnL-F spacers, and the trnL intron). In Ceropegieae, the analyzed taxa fall in four subclades. The Heterostemma subclade is sister to other three subclades, of which the Conomitra-Leptadenia-Orthanthera subclade is sister to the Anisotoma-Neoschumannia-Riocreuxia-Sisyranthus subclade and to the large subclade comprising the stem-succulent stapeliads, Brachystelma and Ceropegia. Following these results, subdivision of Ceropegieae into four subtribes, Anisotominae, Heterostemminae, Leptadeniinae and Stapeliinae, is proposed.

CEROPEGIA (APOCYNACEAE, CEROPEGIEAE, STAPELIINAE): PARAPHYLETIC BUT STILL TAXONOMICALLY SOUND1

Abstract Even though the species-rich genus Ceropegia L. (Apocynaceae, Ceropegieae) is convincingly characterized by its pitfall flowers, investigation of non-coding markers of chloroplast DNA (cpDNA) (trnT-L and trnL-F spacers and the trnL intron) and nuclear ribosomal DNA (nrDNA) (ITS) has shown that Ceropegia is twice paraphyletic. The 36 analyzed Ceropegia taxa scatter over a grade of seven clades. One clade is shared by Ceropegia and all Brachystelma R. Br. species investigated, making Ceropegia (without Brachystelma) paraphyletic. All endemic Madagascan Ceropegia taxa investigated and the East African C. robynsiana Werderm. share a terminal, but not further-resolved clade with the stapeliads. Thus, again, Ceropegia without the stapeliads is paraphyletic. These results are incongruent with current taxonomy. In the absence of adequate morphological, anatomical, or karyological characters supporting a taxonomic reclassification of the genus in accordance with the retrieved clades of the phylogenetic analysis, it is proposed that the current taxonomy be maintained.

Cibirhiza albersiana, a new species of Asclepiadaceae, and establishment of the tribe Fockeeae

In the course of a long-term study of African Cynanchinae, several specimens of a remarkable, undetermined asclepiad from E. Africa were found in the Kew Herbarium (K). Its pollinarium structure shows strong similarity with that of Cibirhiza dhofarensis Bruyns and Fockea Endl. specimens. Anther morphology and basic corona structure agree with that of Cibirhiza, a genus established recently by Bruyns (1988). Since some important aspects remain unclear in his description, a detailed structural analysis of C. dhofarensis was necessary. Our specimens show a striking similarity to C. dhofarensis but some marked deviations in staminal corona morphology. Therefore, it seems appropriate to describe our E. African material as a new species of the genus Cibirhiza, C. albersiana. Between Fockea and the remainder of the Marsdenieae major differences have been noted several times in the past (e.g. Kunze, 1990, 1993) but systematic consequences have not been drawn yet. Our present anlysis supports the removal of Fockea from the Marsdenieae and the creation of a new tribe, Fockeeae, containing the two genera Fockea and Cibirhiza.

Deceptive Ceropegia dolichophylla fools its kleptoparasitic fly pollinators with exceptional floral scent

Ceropegia species (Apocynaceae) have deceptive pitfall flowers and exploit small flies as pollinators, supposedly by chemical mimicry. Only preliminary data on the composition of flower scents are available for a single species so far, and the mimicry system is not yet understood in any species. We collected data on basic pollination aspects of C. dolichophylla, analyzed floral scent by gas chromatography linked to mass spectrometry, identified electrophysiologically active scent components by gas chromatography coupled with electroantennographic detection, and determined compounds responsible for pollinator attraction in bioassays. We found that flowers of C. dolichophylla are visited by small flies of several taxa. Only Milichiidae and Chloropidae carried pollinaria and are, thus, pollinators. The pollen transfer efficiency at two different sites was 2 % and 4 %, respectively. The floral scent was dominated by spiroacetals, mainly (2S,6R,8S)-8-methyl-2-propyl-1,7-dioxaspiro[5.5]undecane, n-tridecane, and N-(3-methylbutyl)acetamide. This spiroacetal and the acetamide elicited the most intense electrophysiological responses in fly antennae, and bioassays confirmed the capability of the spiroacetal in eliciting behavioral responses in pollinators. Most flies, determined as pollinators of C. dolichophylla, are kleptoparasites. They exploit insect prey of predatory arthropods as food source to which they are attracted by volatiles. 8-Methyl-2-propyl-1,7-dioxaspiro[5.5]undecane and N-(3-methylbutyl)acetamide have not been identified before as volatiles of other plants, however, they are known as insect volatiles. Both compounds occur in the venom glands of paper wasps, a potential food source for the pollinators of C. dolichophylla. We propose that C. dolichophylla shows a kleptomyiophilous pollination strategy. It mimics insect related odors to exploit the food-seeking behavior of its kleptoparasitic pollinators.

A Karyological Survey of Asclepiadoideae, Periplocoideae, and Secamonoideae, and Evolutionary Considerations within Apocynaceae s.l

The chromosome numbers of 672 species out of 740 taxa of the Apocynaceae in the subfamilies Asclepiadoideae, Periplocoideae, and Secamonoideae were either determined or extracted from the literature. The chromosome numbers of 299 taxa are published here for the first time, and a further 139 new counts confirm or complete previously published chromosome numbers. The basic chromosome number x = 11 is found to be predominant, occurring in ca. 96% of the taxa investigated. Deviations from x = 11 are absent in Periplocoideae and Secamonoideae, but some variation is present in Asclepiadoideae. A reduction of the karyotype to x = 10 is known only in the advanced tribe Asclepiadeae, where it is important in the Old World subtribe Astephaninae (Microloma), as well as in the New World subtribes Metastelminae (Funastrum, Orthosia, Philibertia, and Grisebachiella) and Oxypetalinae (Araujia and Tweedia). An increase (x = 12, 13, 14) was found only rarely and sporadically in the subfamily Asclepiadoideae. About 6% of the species (7% of the taxa) investigated are found to be polyploid. The majority of such taxa are tetraploid with 2n = 44; only a few are hexaploid or higher. The data on chromosome number and size presented in this paper are interpreted in relation to the systematic position and geographical distribution of the taxa investigated. On the average karyotype size diminishes from rather large chromosomes in the Periplocoideae to the smallest karyotype length in the presumed most advanced tribe of the Asclepidoideae, the Asclepiadeae. Reduction in the basic chromosome number is regarded as only a rather recent step in genome evolution within Asclepiadeae, which has been taken place in parallel in the Old and New Worlds. Finally, comparision with data available for the Apocynaceae s. str. (Apocynoideae and Rauvolfioideae) is presented.

Inclusion of Tenaris and Macropetalum in Brachystelma (Apocynaceae-Asclepiadoideae-Ceropegieae) inferred from non-coding nuclear and chloroplast DNA sequences

Abstract. The inclusion of Tenaris and Macropetalum in Brachystelma as proposed by Peckover in 1996 and contested by Victor and Nicholas in 1998 is supported by molecular studies. Parsimony analysis of sequence data from two non-coding molecular markers (ITS region of nrDNA and trnT-L and trnL-F spacers as well as the trnL intron of cpDNA) suggests a well-supported Brachystelma s.l. clade (including Tenaris and Macropetalum) with little internal resolution. The Brachystelma s.l. clade occupies a sistergroup position to the Ceropegia/stapeliad clade, and both clades together are sister to an Anisotoma/Sisyranthus/Neoschumannia clade.