We investigated the historical biogeography of the Inuleae–Plucheinae (Asteraceae), a group of arid-adapted plants with partly unresolved generic circumscriptions, in order to understand its origin and spatiotemporal evolutionary history in relation to the Cenozoic climate shifts. Location Global, with highest species diversity in the Southern Hemisphere. The spatiotemporal biogeography of the Plucheinae was estimated by both a discrete method using a set of general distribution areas, and a relaxed random walk based on extant species distributions. The topology was time calibrated using a combination of secondary node ages and secondary derived rates for included loci. Our results indicate the median age of the Plucheinae to be approximately 15.4 Ma. The biogeographical analyses infer an ancestral origin in southern Africa, with the relaxed random walk analysis narrowing the uncertainty down to an area reaching from coastal Namibia to the western Kalahari. Africa was colonized in a (south)western–(north)eastern direction following the spread of arid habitats. Ancestral representatives of the Plucheinae colonized South America on at least three separate occasions (13.0–4.0, 4.3–3.1 and 4.1–3.7 Ma), with one subsequent spread to North America. Australia was colonized three times between 3.6 and 0.4 Ma. Madagascar and the Mascarenes were colonized at least seven times. The origin of the Plucheinae is estimated to the Namib region, with early speciations and radiations concurring with the timing of aridification of southern Africa, following the increase in strength of the Antarctic Circumpolar Current and subsequent formation of the Benguela Upwelling at c. 11.8 Ma. The current biogeographical distribution of the Plucheinae is best explained by several Neogene long-distance dispersal events from tropical Africa.
The taxonomic positions and phylogenetic relationships of six Pavetteae species endemic to Madagascar were tested with a phylogenetic study of the Afro-Madagascan representatives of the tribe Pavetteae based on sequence data from six markers rps16, trnT-F, petD, accD-psa1, PI and ITS. The six species were resolved into four well-supported and morphologically distinct clades which we here formally recognise at generic level. The new genera are the monospecific Exallosperma and Pseudocoptosperma, each with a single species, and Helictosperma and Tulearia, each with two species. Each genus is characterised by one or more autapomorphies or by a unique combination of plesiomorphic characters. Mostly, the distinguishing characters are found in fruit and seed; Exallosperma differs from all other Pavetteae genera by the fruit consisting of two stony pyrenes, each with a single laterally flattened seed with irregularly distributed ridges on the surface; Helictosperma is unique by its single spherical seed rolled-in on itself in the shape of a giant pill-millipede. Pseudocoptosperma is characterised by the combination of three ovules pendulous from a small placenta and triangular stipules with a strongly developed awn, whereas Tulearia is characterised by robust sericeous flowers, small leaves, uni- or pauciflorous inflorescences and fruits with two pyrenes, each with a single ruminate seed.
The four new genera show marked adaptations to the dry habitats in which they grow. They represent multiple radiations into drylands and highlight the importance of the dry forest and scrub vegetation in western, southern and northern Madagascar for plant biodiversity. The description of the four new genera shows that the tribe Pavetteae exhibits the same pattern as many plant groups in Madagascar, which are characterised by a high proportion of endemic genera comprising a single or a few species.
The pantropical genus Margaritopsis C. Wright (Rubiaceae, Palicoureeae) was recently separated from Psychotria L. and transferred to a different tribe, Palicoureeae, based on both molecular and morphological data. Margaritopsis has been studied in the Neotropics, and in Africa as Chazaliella E.M.A. Petit & Verdc. ; the species that belong to this group in the Pacific are enumerated for the first time here. Recently Eumachia DC. was found to be an older name for this group, and a few species of Margaritopsis have been transferred nomenclaturally to that genus. Here Eumachia is surveyed comprehensively for the first time, with a list of species and an overview of morphological characteristics. The remaining species of Margaritopsis are nomenclaturally transferred here to Eumachia, along with one species of Hodgkinsonia F. Müll., one species of Mapouria Aubl., and several species of Psychotria from Asia, Australia, New Guinea, and the Pacific region. In this new circumscription Eumachia includes 83 species, and is characterized within Palicoureeae by a yellowish green drying color ; stipules that are persistent or fall by fragmentation and are generally glandular when young and hardened when old ; green to whitened inflorescence axes ; white to cream or yellowish green, often rather small corollas ; orange to red fruits ; pyrenes with marginal pre-formed germination slits and no ethanol-soluble pigments ; and non-ruminate endosperm. Eumachia includes 20 species, 8 subspecies, and 7 varieties in Africa, 27 species in the Neotropics, and 36 species and 6 varieties in Asia, Australasia, and the Pacific region. Here we publish 81 new nomenclatural combinations in Eumachia and two new synonymies for Neotropical names, and 11 names from various regions are lectotypified.
Ormocarpopsis anosyana Thulin & Razafim. (Fabaceae), a new species from the Anosy Region of south-eastern Madagascar, is described and illustrated. According to phylogenetic analyses based on nuclear ribosomal ITS sequences, the new species is, with strong support, sister to Ormocarpopsis mandrarensis Dumaz-le-Grand, another species confined to southeastern Madagascar. Ormocarpopsis anosyana differs markedly from Ormocarpopsis mandrarensis by its generally smaller leaflets with the secondary and tertiary venation drying more or less blackish beneath, by its shorter hypanthium, by its smaller calyx with the lowest tooth about as long as the others, by its wing-petals that are much longer than the keel, by its glabrous ovary, and by its slightly articulated fruits. Ormocarpopsis anosyana is known only from two collections from a single patch of spiny dry forest east of Imonty. It is assigned a preliminary conservation status as “Endangered”.