Résumé
Local people's perceptions of cultivated and wild agrobiodiversity,
as well as their management of hybridization are still understudied in
Amazonia. Here we analyze domesticated treegourd (Crescentia cujete),
whose versatile fruits have technological, symbolic and medicinal uses. A
wild relative (C. amazonica) of the cultivated species grows spontaneously
in Amazonian flooded forests. We demonstrated, using whole chloroplast
sequences and nuclear microsatellites, that the two species are strongly
differentiated. Nonetheless, they hybridize readily throughout Amazonia
and the proportions of admixture correlate with fruit size variation of
cultivated trees. New morphotypes arise from hybridization, and are
recognized by people and named as local varieties. Small hybrid fruits are
used to make the important symbolic rattle (maracá), suggesting that
management of hybrid trees is an ancient human practice in Amazonia.
Effective conservation of Amazonian agrobiodiversity needs to incorporate
this interaction between wild and cultivated populations that is managed
by smallholder families. Beyond treegourd, our study clearly shows that
hybridization plays an important role in tree crop phenotypic
diversification, and that the integration of molecular analyses and
farmers'perceptions of diversity help disentangle crop domestication
history.