Format: ORAL

Nantenaina H. Rakotomalala1,Lorna MacKinnon2,Fenitra N. Randrianarimanana 1,Sami Touafchia3,Thomas Haevermans3,George Burton2,Rafael F. de Almeida2,Jean A. Randriamampianina4,Mijoro Rakotoarinivo5,Maria S. Vorontsova2

1 Royal Botanic Gardens Kew, Antananarivo, Madagascar 2 Royal Botanic Gardens Kew, London, United Kingdom 3 Museum National d'Histoire Naturelle Paris 4 National Centre for Applied Research on Rural Development (FOFIFA), Madagascar 5 University of Antananarivo, Madagascar

The Poaceae family is species-rich and functionally significant for Madagascars ecosystems and agrisystems. As part of an interdisciplinary project on grass diversity and agricultural interactions, we revise the classification of the genus Digitaria in Madagascar. This complex group poses identification challenges due to strong similarities between species. Over 50% of the 14,000 Madagascars Poaceae herbarium collections are housed in Paris, presenting a constraint for Malagasy botanists aiming to study grass microscopic features that are not discernible in digital images. Consequently, I undertook trips to both Paris and London to access the essential resources, supplementing fieldwork efforts. Through examination of herbarium materials and field collections, we identified 30 species in Madagascar, including seven endemics, and excluding five species previously believed to occur in the region. Noteworthy are a likely new species from central and northern Madagascar and a new record of D. ternata. Three names were placed in synonymy: endemics D. psammophila and D. planiculmis are synonyms of the non-endemic D. didactyla, while D. madagascariensis is a synonym of the endemic D. fulva. A key to the species is provided along with illustrations, descriptions, and distribution information. This revision updates the Digitaria data in the Weed Identification and Knowledge in the Tropical and Mediterranean Areas portal.Using the updated species concepts, ethnobotanical analyses revealed 11 Digitaria species considered to be weeds affecting agriculture and used as forages in the highlands. Weedy traits of D. humbertii include its entangling growth habit and the ability to infiltrate cropping systems. Phylogenetic analysis indicates independent evolution of weedy species in the paraphyletic Digitaria clade. In order to disseminate these findings,we created an illustrated field guide in English and Malagasy, developed collaboratively with national agricultural institutions and the Ministry of Agriculture to help farmers recognize native forages and identify weed control methods.