Economic Botany: Evolution of Cultivated Plants
Hughes, Colin E. , Govindarajulu, Rajanikanth , Robertson, Ashley , Filer, Denis L. , Harris, Stephen A , Bailey, C. Donovan .
Beans in the Basura: Serendipitous Backyard Hybridization in Leucaena (Fabaceae).
The historical collection and translocation of seeds for consumption or local cultivation have long been considered important processes in the early evolution and domestication of crops. Artificial sympatry of taxa resulting from intentionally cultivated or discarded seed can spawn serendipitous hybrids and the generation of new phenotypes. The impacts of human translocation and serendipitous hybridization are widely discussed in the literature, but there is often sparse empirical evidence demonstrating these processes for crop species. Using archaeological, ethnobotanical, geographical, and genetic data, we investigate the extent and significance of predomestication cultivation, backyard sympatry, spontaneous hybridization and polyploidy for the Mimosoid legume tree Leucaena, which is used as a food crop throughout south-central Mexico. We show that predomestication cultivation was widespread, involved numerous independent transitions from the wild to cultivation, and resulted in extensive artificial sympatry of 2–6 species locally and 13 species in total. Comparing gene trees derived from chloroplast and rapidly evolving biparentally inherited nuclear-encoded DNA sequences, we demonstrate that hybridization in Leucaena has been extensive, spawning a diverse set of novel hybrids as a result of juxtaposition of species in cultivation. Furthermore, these data provide evidence for allopolyploid origins of the tetraploid Leucaena species, four of five of which are important local or regional food crops. These findings suggest that backyard hybridization and polyploidy have played a central role in Mesoamerican crop domestication and demonstrate that the simple step of bringing species together in cultivation can provide a potent trigger for domestication.
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1 - University of Oxford, Department of Plant Sciences, South Parks Road, Oxford, Oxfordshire, OX1 3RB, United Kingdom
2 - New Mexico State University, Biology, PO Box 30001 Dept 3AF, Las Cruces, NM, 88003, USA
3 - Oxford University, Plant Sciences, Oxford, OX1 3RB, UK
4 - New Mexico State University, Department of Biology, Po Box 30001, Department 3Af, Las Cruces, New Mexico, 88003-8001, USA
Presentation Type: Oral Paper:Papers for Topics
Date: Wednesday, July 30th, 2008
Time: 1:45 PM