The unmanaged reproductive ecology of domesticated plants in traditional agroecosystems: An example involving cassava and a call for data

Although cassava is a strictly vegetatively propagated crop, in many tradit ional Amazonian agroecosystems, Amerindian farmers recognise volunteer seed lings of cassava and allow them to grow. If their properties are deemed des irable, plants originating from seedlings are included in the harvest of tu berous roots, and their stems are used to prepare cuttings for propagation. Incorporation of these products of spontaneous sexual reproduction appears to be important in origin and maintenance of genetic diversity in this clo nally propagated plant. Our observations conducted in an Amerindian village in Guyana suggest that volunteer seedlings arise from a bank of viable see ds stored in soil, and that dispersal and burial of seeds by ants may be im portant in its constitution. Future investigations of the dynamics of genet ic diversity in this crop in traditional agroecosystems must consider the r ole of the 'wild' sexual reproduction that occurs in parallel with vegetati ve propagation. We suggest that unmanaged processes of sexual reproduction play important but neglected roles in the evolutionary ecology of many dome sticated plants in traditional agroecosystems. (C) 2000 Editions scientifiq ues et medicales Elsevier SAS.