Historical biogeography of olive domestication (<i>Olea europaea</i>L.) as revealed by geometrical morphometry applied to biological and archaeological material

TLDR

The study aims to elucidate the historical biogeography of olive domestication in the Mediterranean, especially the north‑western region, and proposes a diffusion model for olive cultivation. Researchers applied traditional and geometrical morphometrics, including size‑standardized polynomial regression, to olive stones from wild populations, cultivated varieties, and archaeological assemblages across Spain, France, and Italy. Morphometric analysis distinguished wild from cultivated olives, mapped geographic and temporal variation, and provided evidence that olive domestication originated indigenously in the north‑western Mediterranean during the Bronze Age.

Abstract

Abstract Aim This study intends to improve our understanding of historical biogeography of olive domestication in the Mediterranean Basin, particularly in the north‐western area. Location Investigations were performed simultaneously on olive stones from extant wild populations, extant cultivated varieties from various Mediterranean countries, and archaeological assemblages of Spanish, French and Italian settlements. Methods A combination of morphometrics (traditional and geometrical) allowed us to study both the size and shape of endocarp structure. Concerning shape, a size‐standardized method coupled with fitted polynomial regression analysis was performed. Results We found morphological criteria for discriminating between wild and cultivated olive cultivars, and established patterns of morphological variation of olive material according to the geographical origin (for extant material) and to the age of the olive forms (for archaeological material). Levels of morphological convergences and divergences between wild olive populations and cultivated varieties are presented as evidence. Main conclusions Morphological changes of endocarps of olive under domestication at both geographical and chronological scales provide new criteria for the identification of olive cultivars. They allow to determine the origins of cultivated forms created and/or introduced in the north‐western Mediterranean regions and to understand how human migrations affected the rest of the Western Mediterranean regions. A model of diffusion of olive cultivation is proposed. It shows evidence of an indigenous origin of the domestication process, which is currently recognized in the north‐western area since the Bronze Age.