Insights into the historical biogeography of the date palm (Phoenix dactylifera L.) using geometric morphometry of modern and ancient seeds
Article first published online: 19 DEC 2011
© 2011 Blackwell Publishing Ltd
Journal of Biogeography
Volume 39, Issue 5, pages 929–941, May 2012
How to Cite
Terral, J.-F., Newton, C., Ivorra, S., Gros-Balthazard, M., de Morais, C. T., Picq, S., Tengberg, M. and Pintaud, J.-C. (2012), Insights into the historical biogeography of the date palm (Phoenix dactylifera L.) using geometric morphometry of modern and ancient seeds. Journal of Biogeography, 39: 929–941. doi: 10.1111/j.1365-2699.2011.02649.x
Present address: Laboratoire d’Archéologie et de Patrimoine, Université du Québec à Rimouski, 300 allée des Ursulines, Rimouski, QC G5L 3AI, Canada.
Present address: Ecosystem Management, Department of Environmental Science, ETH Zürich, Universitätstrasse 16, Zurich 8092, Switzerland.
- Issue published online: 17 APR 2012
- Article first published online: 19 DEC 2011
- date palm;
- elliptic Fourier transforms;
- historical biogeography;
- Phoenix dactylifera;
- seed shape
Aim The main purpose of this work is to understand the origin, history, historical biogeography and mechanisms of date palm (Phoenix dactylifera L.) domestication.
Location Seeds of uncultivated Phoenix individuals from isolated Oman populations, cultivated date palm varieties of various geographical origins and other related Phoenix species were analysed. Additionally, well-preserved seeds from Egyptian archaeological sites (14th century bc to 8th century ad) were compared with the morphometric reference model based on the analysis of modern material.
Methods Elliptic Fourier transforms (EFT), a morphometric method applied to shape outline analysis, were used to characterize seed shape and to quantify morphological diversity in P. dactylifera and related species.
Results Analysis of seed outlines by EFT (1) showed that P. dactylifera can be differentiated from other Phoenix species and (2) enabled the quantification of patterns of shape differentiation in the genus Phoenix at different taxonomic, geographical and chronological levels. Date palm agrobiodiversity, partitioned in distinct morphotypes, appeared to be complex in terms of geographical structure. Allocation of archaeological seeds to different modern Phoenix forms and date palm morphotypes allowed us to reveal ancient forms consumed and/or exploited in Egypt and finally to determine spatial and temporal changes in agrobiodiversity.
Main conclusions Based on the morphological diversity quantified in P. dactylifera and related species, we characterized ancestral seed shape features present in uncultivated populations. The geographical distribution pattern of seed shapes points to human dispersal routes that spread cultivation from one or more initial ‘domestication centres’. Finally, this work provides a powerful tool to identify ancient forms as demonstrated by the analysis of well-preserved Egyptian archaeological seeds, dating from the 14th century bc to the 8th century ad. Results open new and fascinating perspectives on the investigation of the origins and chrono-geographical fluctuation of date palm agrobiodiversity.