Jean-Noël Labat

NEOENDEMISM IN MADAGASCAN SCALY TREE FERNS RESULTS FROM RECENT, COINCIDENT DIVERSIFICATION BURSTS

Abstract More than 80% of Madagascars 12,000 plant species are endemic with the degree of endemism reaching as much as 95% in the scaly tree ferns, an important species rich component of Madagascars evergreen rainforests. Predominantly African or Asian ancestry and divergence times usually postdating the separation of Madagascar from the Gondwanan landmasses have been demonstrated for several Madagascan animal and angiosperm groups. However, evolutionary studies of rainforest-specific lineages are scarce and the ecological context of radiation events has rarely been investigated. Here, we examine the evolution of Madagascan tree ferns as a rainforest-specific model family, integrate results from bioclimatic niche analysis with a dated phylogenetic framework, and propose an evolutionary scenario casting new light on our knowledge of the evolution of large island endemic clades. We show that Madagascars extant tree fern diversity springs from three distinct ancestors independently colonizing Madagascar in the Miocene and that these three monophyletic clades diversified in three coincident radiation bursts during the Pliocene, reaching exceptionally high diversification rates and most likely responding to a common climatic trigger. Recent diversification bursts may thus have played a major role in the evolution of the extant Madagascan rainforest biome, which hence contains a significant number of young, neoendemic taxa.

Implications of a molecular phylogenetic study of the Malagasy genus Cedrelopsis and its relatives (Ptaeroxylaceae).

Ptaeroxylaceae is an Afro-Malagasy family containing three genera, Bottegoa, Cedrelopsis, and Ptaeroxylon. Although the family is morphologically well delimited, it is currently considered part of the subfamily Spathelioideae in a broadly circumscribed orange family (Rutaceae). The Malagasy Cedrelopsis has traditionally been associated with different families of the order Sapindales and its phylogenetic placement in Rutaceae sensu lato has yet to be tested with molecular data. The present molecular phylogenetic study reaffirms the monophyly of Ptaeroxylaceae and its placement in Spathelioideae. Therefore, molecules and morphology support close affinities between Bottegoa, Cedrelopsis, and Ptaeroxylon and also their current generic circumscriptions. We report a case of an evolutionary change from one-seeded to two-seeded carpels within the Harrisonia-Cneorum-Ptaeroxylaceae clade of Spathelioideae. Finally, the sister-group relationship between the African Bottegoa and the Afro-Malagasy Ptaeroxylon-Cedrelopsis clade suggests an African origin of Cedrelopsis.

Chaos revisited: nomenclature and typification of the Malagasy endemic Euphorbia subgenus Lacanthis (Raf.) M.G.Gilbert

Haevermans T., Rouhan G., Hetterscheid W., Teissier M., Belarbi K., Aubriot X. & Labat J.-N. 2009. — Chaos revisited: nomenclature and typification of the Malagasy endemic Euphorbia subgenus Lacanthis (Raf.) M.G.Gilbert. Adansonia, sér. 3, 31 (2): 279-299. ABSTRACT Malagasy relatives of the Crown-of-Thorns (Euphorbia milii Des Moul.) are well known worldwide for their ornamental value. Malagasy taxa account for almost 10% of the genus Euphorbia L., with 110 accepted names constituting subgenus Lacanthis (Raf.) M.G.Gilbert. The chaotic taxonomy combined with the poor state of preservation of most herbarium specimens makes the systematic study of this huge genus a quite difficult task. This paper offers a nomenclatural account of all the published names with a recapitulatory list citing all the accepted names in subgenus Lacanthis as a first step towards the revision of the group.

A Synoptic Revision of the Malagasy Endemic Euphorbia pervilleana Group

Abstract The non-succulent, leafy species of Euphorbia from Madagascar have received considerably less attention from taxonomists than the succulent Euphorbia species. The lack of a recent synthetic taxonomic treatment for this group makes it almost impossible to accurately name these species. As part of an ongoing revision of the genus in Madagascar, Euphorbia randrianjohanyi and Euphorbia rauhii, two new species closely allied to the Malagasy endemic E. pervilleana are described, and a key to these three species is provided. This group is distinguished by echinate 1–2-locular capsules. It is closely related to other Malagasy species such as E. tetraptera, which possesses 2-locular capsules with four wings. The three species are dioecious and their deciduous leaves can make some specimens difficult to distinguish; however they can be separated by their allopatric distribution, the length of interglandular appendages, the shape and size of the leaves, as well as by fruit features. They all occur in the central and southern part of the island.

A New Species of Caryota (Arecaceae, Coryphoideae) from Central and North Sulawesi

Abstract A new species of Caryota, endemic to north and central Sulawesi, is described and illustrated. A key is provided to distinguish Caryota angustifolia from the other five species of Caryota occurring to the east of Wallaces line.