Conservation assessment of cassava wild relatives in central Brazil

Abstract

Crop wild relatives (CWR) are a key component of the world’s biota since they have the potential to contribute traits for crop improvement. The rich flora of the Brazilian Cerrado harbours a large number of CWR, but little is known about their distribution and conservation status. This study focused on the conservation of cassava (Manihot) wild relatives in the Cerrado. To accomplish this, we performed herbarium and field surveys to assess species conservation status based on geographic distribution, population density estimates, and rates of habitat loss. We found 75 species of Manihot occurring in the Cerrado, including 59 endemics. Among the endemic taxa, 24 are at some level of threat according to IUCN classification (14% Vulnerable, 22% Endangered, 5% Critically endangered), mostly owing to narrow geographic range and habitat loss. Most species are locally abundant, ranging from 55 to 1493 mature individuals per hectare. A quarter of the species recorded have been described over the past 5 years, indicating that the diversity of Manihot in the Cerrado is still underestimated. Areas of high species richness and endemism coincided mostly with Cerrado highlands, particularly in northern Goias state. Field surveys in 16 reserves indicate that 54% of Cerrado endemics are not represented in these protected areas. We believe that the patterns of distribution and conservation status uncovered here for Manihot are representative of many plant groups that are particularly diverse in high-altitude areas in the Cerrado. This calls for expansion of the network of protected areas to cover a wider range of environments, particularly those with a concentration of rare and endemic species, to ensure the effective in situ conservation of CWR present in the Cerrado flora.