Phylogeny and taxonomy of Afrocayratia,a new genus of Vitaceae from continental Africa and Madagascar

The genus Cayratia Juss. in the traditional sense (i.e., Cayratia s.l.) of the grape family has been shown to be non‐monophyletic. Previous studies supported the splitting of Cayratia s.l. into three genera, that is, Cayratia s.s., Causonis Raf., and a new genus representing the African Cayratia clade. However, the morphology of the African Cayratia clade has not been studied carefully and its phylogenetic position within Vitaceae remains unclear. Our study integrates molecular, distributional, and morphological data and supports the recognition of the new genus Afrocayratia from continental Africa and Madagascar. Phylogenetic analyses strongly support the monophyly of Afrocayratia and resolve it as a sister of Cayratia s.s. based on the chloroplast data, but it is placed sister to Cyphostemma based on the internal transcribed spacer dataset. Molecular dating suggests that Afrocayratia split with Cayratia s.s. during the Paleocene, but that the extant species of Afrocayratia did not diversify until the early Miocene. Afrocayratia differs from its allied genera in having short stigmas and seeds with subcircular ventral infold cavities in cross‐section. Three clades are detected within Afrocayratia, with A. debilis (Baker) J.Wen & L.M.Lu as the first diverged lineage. The second diverged lineage includes A. delicatula (Willems) J.Wen & Z.D.Chen and A. gracilis (Guill. & Perr.) J.Wen & Z.D.Chen. The third diverged lineage includes A. imerinensis (Baker) J.Wen & L.M.Lu, A. longiflora (Desc.) J.Wen & Rabarijaona, and A. triternata (Baker) J.Wen & Rabarijaona from Madagascar, which form a monophyletic group that diverged from the second lineage in the middle Miocene. Combining the morphological and molecular evidence, we formally describe the new genus Afrocayratia, make seven new combinations, and provide a key to species of the genus.     

Geographic variation of fruit scents in a dispersion mutualism,the case of Ficus lutea

Chemical mediation is often involved in interactions between plants and animals, as in pollination and in seed dispersion mutualisms. Extensive investigation has been done in floral scents and on their interspecific and intraspecific variations, but similar research on fruit scent remains poorly explored and only focused on interspecific variations. We investigated in this study the intraspecific variations of volatile bouquet emitted by mature fruits of Ficus lutea, in two sites within its wide distribution range, i.e. in South Africa and in Madagascar. We demonstrated a clear geographic variation in the volatile bouquet emitted by ripe figs in these two study sites, especially due to the presence of sesquiterpenes in Madagascan bouquets, while scents present at both sites high amounts of fatty acid derivatives. We discuss here different possible explanations for such variations in fruit scents, potentially resulting from insular and/or geographic isolation. This novel result of an intraspecific variation linked to fig seed dispersion serves to increase our knowledge of the role of scents in seed dispersal mutualisms.     

Hawk-moth scale analysis and pollination specialization in the epilithic Malagasy endemic Aerangis ellisii (Reichenb. fil.) Schltr. (Orchidaceae)

The pollination biology of the epilithic endemic Aerangis ellisii (Reichenb. fil.) Schltr. (Orchidaceae) was studied on an inselberg in the Antananarivo region, central Madagascar. The flowers exhibit long nectariferous spurs indicative of hawk-moth pollination, the mechanism evidently involving pollinia transfer via the frons and palpi of the vectors. Analysis of hawk-moth scales on naturally pollinated stigmas showed that the principal pollinators were Agrius conuolvuli (Linnaeus) and Panogena lingens (Butler). Proboscis morphology of long-tongued Malagasy Sphingidae in relation to nectar position and spur morphology in A. ellisii also indicated that A. conuolvuli and P. lingens were best suited to interact with the plant's floral adaptation. Aerangis ellisii seems to display a relatively moderate specialization versus the Malagasy hawk-moth guild since its nectar is accessible even to those long-proboscis hawk-moth species which are not able to act as pollinators.     

Relationships of the MadagascarBignoniaceae: A striking case of convergent evolution

Most MadagascarBignoniaceae have indehiscent fruits and have been assigned to the tribeCrescentieae. As thus constituted, theCrescentieae are remarkably disjunct between Central America (and the West Indies) and Madagascar with a single monotypic genus also on continental Africa. This paper analyzes the evolutionary relationships of the MadagascarCrescentieae and concludes that they are descended from a different ancestral stock than the New WorldCrescentieae. A revised tribal taxonomy is proposed to reflect phylogenetic relationships withCrescentieae restricted to the neotropic species andColeeae resurrected for the indehiscent-fruited Madagascar species.