Yams of Madagascar: systematics, conservation and sustainable use

This project seeks to deliver understanding of the diversity of yams in Madagascar. The knowledge obtained is being used to work towards threatened species conservation and sustainable utilization of populations critical for the food security of rural people in Madagascar.

A female plant of Dioscorea ovinala, an important edible yam from Madagascar, showing the leaves and fleshy immature capsules

The yams of Madagascar are unique in three ways: 1) in their degree of endemism (most belong to an endemic clade, which represents one of the main lineages within Dioscorea); 2) almost all species have edible tubers; and 3) the endemic taxa are extracted from forest as wild plants, rather than being cultivated. The rural population, especially in areas outside the central highlands, rely on these wild yams to supplement the unreliable rice harvest. Introduced species such as D. alata and D. esculenta are cultivated.

This project began as a systematic revision of the species and infraspecific taxa in Madagascar (including from the Comores). Diversity is highest in the seasonal forests of the West and North-West, but yams can be found in all parts of the island. Ten taxa new to science have been discovered in total, including important food resource species such as D. bako and D. orangeana. Five papers have been published since 2006 in peer-reviewed journals covering 20 species, ca 50% of the yams of Madagascar. Research has also yielded a database of over 1,000 georeferenced specimens which has been used to produce distribution data and conservation assessments. In 2011, work has begun to produce a complete treatment of the yams of Madagascar using eTaxonomic methods, specifically a scratchpad, to combine the existing taxonomic publications into a single resource for users.

With the taxonomic discovery phase of the project approaching completion, research effort has begun to move into conservation and sustainable utilisation of the yams of Madagascar. We have started a collaboration with Feedback Madagascar and its partner NGO, Ny Tanintsika (FBM/NT), to develop a programme of community-based conservation and sustainable utilisation of yams in the eastern humid forests. FBM/NT have been working with communities in the Ambositra-Vondrozo Corridor (COFAV) for 17 years to promote integrated development and conservation. COFAV is a flagship protected area being established by the Ministry of Environment and Forests and Conservation International to conserve 2,800 km2 of eastern humid forests. We are promoting the cultivation of high-yielding cultivars of two introduced species, D.alata and D.esculenta, to take pressure off wild species such as D. seriflora, D. madecassa and D. kimiae and to improve food security. We have established successful demonstration plots cultivating D.alata in 12 communities and there has been an enthusiastic uptake by households and significant interest shown by neighbouring communities. We have also completed a nutritional study of 700 households in 30 villages in the COFAV area and plan to follow this with a socio-economic survey enumerating the financial benefits of intensifying yam cultivation and sustainably managing wild species. Further such projects in other regions of Madagascar are planned subject to successful fundraising.