June 23, 2011

Dual origins of cultivated coconuts

PLoS ONE 6(6): e21143. doi:10.1371/journal.pone.0021143

Independent Origins of Cultivated Coconut (Cocos nucifera L.) in the Old World Tropics

Bee F. Gunn et al.

As a portable source of food, water, fuel, and construction materials, the coconut (Cocos nucifera L.) played a fundamental role in human migrations and the development of civilization across the humid tropics. Here we investigated the coconut's domestication history and its population genetic structure as it relates to human dispersal patterns. A sample of 1,322 coconut accessions, representing the geographical and phenotypic diversity of the species, was examined using ten microsatellite loci. Bayesian analyses reveal two highly genetically differentiated subpopulations that correspond to the Pacific and Indo-Atlantic oceanic basins. This pattern suggests independent origins of coconut cultivation in these two world regions, with persistent population structure on a global scale despite long-term human cultivation and dispersal. Pacific coconuts show additional genetic substructure corresponding to phenotypic and geographical subgroups; moreover, the traits that are most clearly associated with selection under human cultivation (dwarf habit, self-pollination, and “niu vai” fruit morphology) arose only in the Pacific. Coconuts that show evidence of genetic admixture between the Pacific and Indo-Atlantic groups occur primarily in the southwestern Indian Ocean. This pattern is consistent with human introductions of Pacific coconuts along the ancient Austronesian trade route connecting Madagascar to Southeast Asia. Admixture in coastal east Africa may also reflect later historic Arab trading along the Indian Ocean coastline. We propose two geographical origins of coconut cultivation: island Southeast Asia and southern margins of the Indian subcontinent.



jack enright said...

You are well grounded in scientific theory with DNA analysis. Do you have an idea about the possible origin of the Coconut, that is the land where it originated? I suppose there are many varieties but I would first think that the species originated in the tropics of Southeast Asia. Using fossil evidence of species it may be possible to find the routes of ancient mariners along the coasts and eventually to distant islands.

desrosiersj said...

Coconuts, and the large family they belong to, seem to come from the Americas. There are very few related species in the old world. The coconuts closest relatives are in South America and Central America. If one sees these species and eats the nuts, there is no doubt. What is not known is how widespread the proto-coconut was before human intervention. DNA divergence estimates would help. My guess is that the coconut distributed itself on ocean currents from the Americas and was first found by humans in the Pacific. It is possible that ancient mariners found it in the Americas first, but I doubt it. It does seem to have evolved in America though.