Etude de la structure génétique du complexe sauvage-cultivé chez le palmier Bactris gasipaes (H.B.K.) en Equateur. Suivi de : étude de la distribution diamétrique de quelques espèces d'arbres dans les forêts tropicales du bassin du Congo

Domestication is an interesting model for studying the evolution of recently diverged species, especialy the hybridization between domesticated plants and their wild relatives. We studied the genetic structure of a crop-wild complex in an American distributed palm tree : Bactris gasipaes (H.BK.). The plant has been cultivated by Amerindian tribes since pre-Columbian times, and is showing nowadays, an increased interest for palm heart production. ln Ecuador a sympatric situation can be found between the wild plant and the domesticated plant, as weil as populations of the wild type occuring alone. A two month study in Ecuador was undertaken to gather information on the Ecuadorian distribution of the species and collect sorne important ecological information. We also genotyped 7 microsatellite loci on 96 individuls representing the genetic diversity of the wild type in Ecuador and the whole diversity of the cultivated plant in America. The crop taxa has a limited ecological range (hygrofile) compared to its wild relative. The wild populations present a very fragmented habitat with low individual density. Our results show that actual gene flow seems to happen between wild and crop populations in the sympatric area. Genetic diversity is significantly greater within the cultivated form than within the wild one in Ecuador. The ecological observations suggest a monophyletic origin of the crop, however the genetic data do not exclude a polyphyletic origin. Wild populations showed significant heterozygote deficiencies, that could be explained by a Walhund effect, mixted mating or homogamie. Low genetic diversity and heterozygote deficiency could reflect a decline of these populations because of a strong disturbance of their habitat. These results have implications for the hypotheses on crop evolution and on strategies for genetic conservation of the wild type.