Aloes and Lilies of Ethiopia and Eritrea

306 DIOSCOREACEAE
Use and
chemistry
Conservation
the Old and New World Tropics; many species in tropical
Asia, and with c. 10 species in Ethiopia and Eritrea.
Several species of Dioscorea are used as a staple food
in the tropics. These tubers are commonly known as
‘Yams’. There has been a developed culture in the
domestication of several species in tropical Africa, Asia
and America. The major species that are used as food
worldwide are: D. alata L., D. esculenta (Lour.) Burkill,
and D. cayenensis­D. rotundata complex. At least 20
others are used as food in times of famine, and also for
medicinal purposes.
A number of species are known to accumulate large
quantities of steroidal saponins in their tubers and
rhizomes. These have been used by the pharmaceutical
industry to develop semi­synthetic corticosteroids and
other sex hormones such as p­pills.
Recent studies made on the Dioscorea species in western
Ethiopia have revealed that the peoples of southern and
western Ethiopia have a strong tradition in cultivating
and domesticating various species with a wide genetic
base. Only one of the species, D. gil let tii, is a nearendemic
occurring in south and southeastern Ethiopia
and northern Kenya, bordering Ethiopia. The remaining
species are non­endemic. Some of the species such as D.
cayenensis-D. rotundata complex occur both in the wild
and in cultivation, and others such as D. abyssinica, D.
dumetorum, D. cochleari-apiculata, D. quar tiniana and
D. schimperiana, occur only in the wild. The removal
of vegetation cover by human activities (for agricultural
expansion and settlement) undoubtedly reduces the
genetic bases of these important cultivated and semicultivated
crops, leading to genetic erosion. Hence the
habitat in which these species occur should be protected.
Due to the difficulty in identifying the species, two types
of keys are constructed using male and female flowers
separately.