The taxonomy and systematics of the flora of Madagascar has greatly benefited from the work done at Kew (by D. Du Puy and collaborators) and in other international institutions (e.g. Missouri Botanical Garden, Muséum d’Histoire Naturelle de Paris). The Malagasy vascular flora was recently estimated to include 243 plant families, 1,730 genera and 11,220 species (Callmander et al., 2011, Plant Ecol. Evol. 144: 121-125). The angiosperms constitute a predominant element of this flora with 10,650 species (84% being restricted to Madagascar). An account of the legume flora of Madagascar estimated that 626 species (of which 70.9% endemic) distributed amongst 113 genera (of which 20.3% endemic) occur on the island. Interestingly, generic diversity in each subfamily in Madagascar compares well to the subfamilial generic diversity on a global scale (28 Caesalpinoideae, 17 Mimosoideae, 68 Papilionoideae). In addition, the family is the third largest family in Madagascar after the Orchidaceae (862 species) and Rubiaceae (660 species). The legume family presents several good reasons to support its choice as a case study for a phylogenetic diversity assessment in Madagascar: i) the family exhibits all major life forms (from herbs to dominant canopy trees); ii) it is extremely well represented in the different vegetation types (although most of the species richness is found in dry forests, there are also several genera restricted to humid forests, e.g. Parkia, or littoral vegetation, e.g. Eligmocarpus); iii) the family has developed numerous associations with bacteria and fungi enabling it to colonize extreme ecosystems. For these reasons it has been suggested that the family is a good proxy to estimate the global diversity of a specific region.
In this project, started in 2011, we will use taxon distribution data, DNA sequences, and the fossil record to study the phylogenetic diversity of Malagasy legumes. Thanks to the work of earlier botanists (especially the late Prof. Jean-Noel Labat) the project benefits from accurate distribution data based on more than 21,000 geo-referenced herbarium specimens. The availability in public repositories of an extensive collection of DNA sequence data, complemented by newly produced sequences, allows the reconstruction of an almost complete genus-level phylogenetic tree of the Malagasy legumes based on the plastid regions matK and rbcL. The Kew Madagascar Conservation Centre (KMCC) and partner institutions have wide ranging collection programmes and we aim to complete the coverage at the genus and species levels within the project. The team will assess the phylogenetic diversity of Malagasy legumes using a 10 km2 grid. Results will be compared with species/genus richness and the observed patterns will be analyzed in relation to abiotic factors, particularly topology and paleoclimate, that could help explain the actual distribution of phylogenetic diversity. This genus-level approach will eventually lead to a species-level assessment of the phylogenetic diversity patterns and a more accurate evaluation of the diversity of this family in Madagascar.
The outcome of this project will allow us to assess the level of phylogenetic diversity already found within the Système d'Aires Protégées de Madagascar (SAPM) and thus propose new target regions to be protected as a priority to ensure that maximum phylogenetic diversity is conserved.This approach is innovative and might provide a quantifiable framework to support the Government of Madagascar and NGOs to target optimal areas for conservation. The current delimitation of the new expanded SAPM is nearing completion, covering 57,000 sq. km or nearly 10% of Madagascar’s land surface, and the Millennium Seed Bank Partnership (MSBP) Madagascar offers an ex-situ conservation strategy for priority taxa and diversity hotspots that fall outside of the SAPM. This project will help refine the MSBP collecting programme to complement in-situ conservation initiatives such as the SAPM and to conserve the most phylogenetically distinct taxa.