Sigrid Liede

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.

A descriptive system for corona analysis inAsclepiadaceae andPeriplocaceae

A general system for description of the corona in theAsclepiadaceae is introduced. It is based on the identification of the components constituting the corona, the relationships among those components, and the relationships among those components and other floral features. The components can be placed in both an evolutionary and ontogenetic context, the latter allowing the identification of homology problems. This approach to corona description reveals certain evolutionary constraints in that some possible combinations of components are not realized.

Circumscription of the Genus Cynanchum (Apocynaceae—Asclepiadoideae)

Abstract Analysis of the trnT-trnL spacer, the trnL intron and the trnL-trnF spacer of 65 species of Cynanchum, 33 members of the Metastelminae, and seven representatives of other Asclepiadeae shows that Cynanchum in its present circumscription is polyphyletic. Both the genus Cynanchum and the subtribe Metastelminae s.l. split along the Old World—New World geographic division. The only exception to this division is Cynanchum subgenus Mellichampia, which belongs to Cynanchum s. str. For the Old World Cynanchum relatives, the subtribe Cynanchinae is re-established. The remaining New World sections of Cynanchum are not monophyletic. The South American members of section Cynanchum join the morphologically aberrant Grisebachiella hieronymi. Section Macbridea is associated with Funastrum. In the Old World, the succulent genera Folotsia, Karimbolea, Platykeleba, and Sarcostemma are monophyletic with stem-succulent Cynanchum and nested within a clade of exclusively Malagasy Cynanchum species. Communicating Editor: Gregory M. Plunkett

Tribal disposition of genera in the Asclepiadaceae

Since the separation of 36 genera of Asclepiadaceae from the Apocynaceae by Brown (1810), the number of genera in the family has steadily increased. Especially the works of Decaisne (1838, 1844) and Bentham (1876) have added numerous new species and genera. The presently recognized c. 250 genera have been classified on a worldwide basis in a number of systems, differing to various degrees in character emphasis and hierarchical arrangement (for discussion of the various systems, see Rosatti, 1989). Bruyns & Forster (1991) have summarized this information and their system has found wide acceptance. They recognize three subfamilies, Periplocoideae, Secamonoideae and Asclepiadoideae. The former two subfamilies comprise one tribe each, the Asclepiadoideae four: Asclepiadeae, Gonolobeae, Marsdenieae and Stapelieae. A fifth tribe of the Asclepiadoideae, the Fockeeae, is presently being delimited (Kunze & al., 1994). These tribes are at least well-circumscribed and easily identifiable taxonomic units, and, in most cases, also most likely monophyletic systematic units (Liede, unpubl.). The monophyly of the Secamoneae has recently been questioned (Klackenberg, 1992), but no better concept has been proposed. The exclusion of the Fockeeae has helped to reduce considerably the heterogeneity of the Marsdenieae; however, the monophyly of the remaining taxa still needs confirmation.

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.

Sarcostemma R.Br. (Apocynaceae — Asclepiadoideae) — a controversial generic circumscription reconsidered: Evidence fromtrnL-F spacers

The polyphyly ofSarcostemma sensu latu, suspected on morphological and karyological reasons is confirmed by analysis of thetrnL-F spacer region. With the exception ofCynanchum montevidense (subgen.Mellichampia, Sundell 1981), Old World and New World taxa belong to different clades.Sarcostemma sensu stricto andPlatykeleba show a strong affinity to Old WorldCynanchum; the affinities ofOxystelma cannot be determined at present.Philibertia andBlepharodon are sister groups, both are sister toFunastrum, andPentacyphus is basal to the New World clade.

Cynanchum and the Cynanchinae (Apocynaceae – Asclepiadoideae): a molecular, anatomical and latex triterpenoid study

Abstract The phylogeny of the genus Cynanchum s. str. is studied using cpDNA spacers and ITS. Morphological, anatomical and latex triterpenoid data are interpreted in light of the molecular results, and discrepancies are discussed. Vegetative characters are better indicators of relationship than floral characters, especially corona characters. The monophyly of all Malagasy species and, nested within the latter, of all stem-succulent taxa is ascertained and the genera Folotsia, Karimbolea, Platykeleba and Sarcostemma are subsumed under Cynanchum. One African species, C. galgalense, is excluded from Cynanchum.

The tribal position of Fockea and Cibirhiza (Apocynaceae: Asclepiadoideae): evidence from pollinium structure and cpDNA sequence data

The pollinium morphology of the two members of the Asclepiadoideae, tribe Fockeeae, Fockea Endl. and Cibirhiza Bruyns, has been studied in detail and compared with that of eight genera of Marsdenieae, the tribe in which Fockea and Cibirhiza were previously accommodated and thus their putative closest relatives, as well as nine genera of Asclepiadeae. Both Fockea and Cibirhiza have several morphological characteristics in common, the most important of which is the absence of well-developed caudicula, which distinguishes them from all other genera of Asclepiadoideae known. The pollinium structure of these two genera, however, differs significantly. Whereas the pollinium of Cibirhiza consists of single pollen grains and is covered by a pollinium wall, as is typical for other Asclepiadoideae, the pollinium of Fockea consists of tetrads and is not covered by a pollinium wall, a condition otherwise typical of Secamonoideae. Fockea, however, has only two pollinia per anther, as does Cibirhiza and all other Asclepiadoideae, whereas the Secamonoideae have four pollinia per anther. Sequence data from two intergenic spacers, trnT-L and trnL-F and the trnL intron of cpDNA was analyzed. The ingroup included three species of Fockea and one species of Cibirhiza. The outgroup taxa consisted of three representatives each of Periplocoideae, and Secamonoideae and 24 species of Asclepiadoideae, including representatives of all tribes, of which eight genera belong to Marsdenieae, as outgroups. The results of the DNA analysis provide strong support for Fockeeae as a monophyletic tribe, distinct from Marsdenieae and, to the rest of the Asclepiadoideae. With the exception of pollen data, all morphological and molecular evidence clearly support recognition of the tribe Fockeeae. The occurrence of two such significantly different types of pollinia structure – characters elsewhere in the family used to distinguish subfamilies – within the small tribe Fockeeae was unexpected, and can perhaps best be understood as yet another attestment to the basal position of the Fockeeae in the nascence of the Asclepiadoideae.

Observations on pollination in Sarcostemma (Asclepiadaceae)

Field observations on pollination in New World species of the genusSarcostemmaR. Br. sensuHolm are reported. Morphological and anatomical comparisons of pollinated flowers ofSarcostemma subg.CeramanthusKuntze (New World) andSarcostemma subg.Sarcostemma (Old World) are presented.