New species from the Galoka and Kalabenono massifs: Two unknown and severely threatened mountainous areas in NW Madagascar

The Galoka mountain chain, comprising principally the Galoka and Kalabenono massifs, situated at the northern edge of the Sambirano Region in NW Madagascar is an area that was virtually unknown botanically. It was visited three times between 2005 and 2007 as part of a floristic inventory. Both massifs contain the last remaining primary forests in the Galoka chain, which extends parallel to the coastline from South of Ambilobe to North of Ambanja. Several new species have been discovered amongst the collections, eight of which are described here. They belong to five families: (i) Annonaceae: Xylopia kalabenonensis D. M. Johnson, Deroin & Callm.; (ii) Araliaceae: Polyscias kalabenonensis Lowry & Callm., Polyscias pachypedicellata Lowry & Callm., Polyscias wohlhauseri Lowry & Callm.; (iii) Malvaceae: Hibiscus lamalama Callm., Buerki & Koopm., Nesogordonia rakotovaoi Rakotoar., Andriambolol. & Callm.; (iv) Meliaceae: Trichilia sambiranensis Callm. & Phillipson; (v) Oleaceae: Noronhia jeremii HongWa & Callm. A summary of the diversity and level of endemism in each genus is provided along with a discussion of the morphological affinities of each of the new species. Because Madagascar's native ecosystems face growing threats, it is crucial to document the island's floristic diversity and provide information for ongoing conservation efforts, e.g., by using the IUCN Red List criteria to assess the threat status of key species. The application of the IUCN criteria shows that all but one of the new species from Galoka chain are "Critically Endangered" (CR) and endemic to the southern part of the massif, whereas Trichilia sambiranensis, which also occurs in other lowland Sambirano forests, is classified as "Endangered" (EN). © Conservatoire et Jardin Botaniques de Genève 2009.