Résumé
Unravelling the origin of present-day populations of plants in relation to the history of Quaternary environmental changes is challenging. In the case of fruit trees, the recurrent exchanges between domesticated and wild populations further complicate reconstructing their natural phylogeographic history. The carob tree (Ceratonia siliqua L.) is a Mediterranean fruit tree that has played a crucial role in societies due to its edible fruits, used as fodder for livestock and in subsistence agriculture. The spread of its cultivation and domestication was linked to the development of grafting methods ca. 3,000 years ago. As for several crops, the Middle East and the Eastern Mediterranean regions were initially proposed as the centre of carob domestication. Based on sound biogeographical assumptions and various molecular data and phylogeographic methods, our results refute this hypothesis. Our analyses support phylogeographic origin from a single refugium situated in south Morocco near the Atlantic coast and that expansion from this refugium has occurred before the Last Glacial and along at least two routes. The absence of clear genetic differentiation of cultivated carobs suggest multiple origins of domestication across its range and from local wild populations. Gene flow and admixture analyses confirm a genetic influence from the East that was probably caused by long-distance dispersal of domesticated varieties. Our studies on the phylogeography and ecology of the carob tree highlight the importance of wild and semi-natural habitats in climatic refugia for the conservation of fruit tree genetic resources.