Revision of the Afro-Madagascan genus Costularia (Schoeneae, Cyperaceae) : infrageneric relationships and species delimitation

A recent molecular phylogenetic study revealed four distinct evolutionary lineages in the genus Costularia s.l. (Schoeneae, Cyperaceae, Poales). Two lineages are part of the Oreobolus Glade of tribe Schoeneae: the first being a much-reduced genus Costularia s.s., and the second a lineage endemic to New Caledonia for which a new genus Chamaedendron was erected. The other two lineages were shown to be part of the Tricostularia Glade of tribe Schoeneae. Based on morphological and molecular data, the genus Costularia is here redelimited to represent a monophyletic entity including 15 species, which is restricted in distribution to southeastern Africa (Malawi, Mozambique, South Africa, Swaziland, Zimbabwe), Madagascar, the Mascarenes (La Reunion, Mauritius), and the Seychelles (Mahe). Molecular phylogenetic data based on two nuclear markers (ETS, ITS) and a chloroplast marker (trnL-F) resolve the studied taxa as monophyletic where multiple accessions could be included (except for Costularia laxa and Costularia purpurea, which are now considered conspecific), and indicate that the genus dispersed once to Africa, twice to the Mascarenes, and once to the Seychelles. Two endemic species from Madagascar are here described and illustrated as new to science, as is one additional species endemic to La Reunion. Two taxa previously accepted as varieties of Costularia pantopoda are here recognised at species level (Costularia baronii and Costularia robusta). We provide a taxonomic revision including an identification key, species descriptions and illustrations, distribution maps and assessments of conservation status for all species

Madagascar Grass Atlas

Madagascar has a unique heritage in terms of biodiversity. Its separation from Africa set the backdrop for the unique evolution of its flora and fauna. Its isolated island nature gave rise to high endemism and explosive speciation. Of its estimated 12,000 vascular plant species, 83% are unique to Madagascar (Madagascar Catalogue, 2019). Its richness in ecosystems and biodiversity have led to its classification as a megabiodiverse country (Mittermeier et al, 2007). Madagascar is home to sixteen contrasting vegetation types defined by Moat and Smith (2007): humid forest, western dry forest, south western dry spiny forest-thicket, bare rock, degraded south western dry spiny forest, western sub-humid forest, mangroves, water, wetland, south western coastal bushland, tapia forest, littoral forest, western humid forest, cultivation, degraded humid forest, plateau grassland-wooded grassland mosaic and wooded grassland-bushland. The dominant vegetation type is the plateau grassland-wooded and grassland-bushland mosaic, covering approximately 65 % of the island (map: vegetation in Madagascar). Research on Madagascar’s grasses is a growing area of interest because of their significance for the national economy as well as conservation. The grass family is the most economically important plant family and has always been closely involved in people’s lives. Grasses provide food: rice (Oryza sativa), maize (Zea mays), sugarcane (Saccharum officinarum) and breadwheat (Triticum aestivum). Grasses also provide food for cattle and building material. Some invasive species threaten crop harvests and conservation of protected areas (FAOSTAT, 2019). Poaceae are one of the largest plant families in Madagascar with an estimated 541 species (Vorontsova et al., 2016). The Royal Botanic Gardens Kew began research on the Poaceae of Madagascar in the 1980s through taxonomic work on the bamboos carried out by Soejatmi Dransfield (see Dransfield 2003). With the growth of KMCC a variety of projects have been carried across Madagascar including checklisting (Nanjarisoa et al. 2017), new records for the country (Vorontsova et al. 2014), and an identification guide (Vorontsova et al. 2018). Five new species have been described: Andropogon itremoensis (Vorontsova et al. 2013), two species of Panicum (Vorontsova 2014), Sartidia isaloensis (Vorontsova et al. 2015) and Digitaria bosseri (Vorontsova 2017). Knowledge has been built on rare endemic grasses: Lecomtella (Besnard et al. 2013), Chasechloa (Silva et al. 2017), and all genera designated as endemic (Vorontsova & Rakotoarisoa 2014). Collaborations have been strengthened between RBG Kew and Malagasy institutions, particularly the University of Antananarivo. In spite of this recent progress in Madagascar grass taxonomy there has been a lack of data on species distributions in Madagascar, a knowledge gap affecting both researchers and policy makers. The majority of specimens are held at the MNHN and available online, but unfortunately internet access is not always available to researchers given its cost and low speed in Madagascar. The Grass Atlas of Madagascar presented here is an output of the GBIF BID project to compile these data and make them accessible to users though the GBIF portal (Rabarivola et al. 2019). It is a reference document on the distribution of Poaceae in Madagascar, which we hope will be useful to decision-makers, researchers and managers of protected areas in Madagascar