The International Work group for Palaeoethnobotany, the only major international meeting in archaeobotany (every 3 years), has its next conference in about a year's time in Greece. Its website it now live. In general this conference has a Eurasian focus. For those with African interests, there is the smaller IWAA, also every three years, and meeting this July.
Monday, 16 April 2012
Tuesday, 3 April 2012
Weed evolution by de-domestication: the case of rice
The study of weed origins and evolutionary history is the poor cousin of the archaeobotany of crop domestication. Archaeobotanists can potentially do much more on this, and undoubtedly should. To provide some inspiration it is worth considering some recent insights from genetics, to do with weedy rice. While it is surely the case that rice's wild progenitors may act as weeds in the crop, it now appears that much weedy rice is descended from the crop and not directly from the wild progenitor. A recent paper in Genetic Resources and Crop Evolution by Zhang et al. explores the variation in weedy rices in southern China (Guangdong) and northeast China (Liaoning). In Liaoning there are no wild progenitor populations so it is cultivated fields or their margins which provide the only real habitat for spontaneous rices. In Guangdong by contrast there are populations of wild O. rufipogon. Based on microsatellite markers they show that weedy rice in each region clusters with crops, which represent indica and temperate japonica rices, and the weedy rices are distant from true wild populations. They take this to support the hypothesis that weedy rice is secondarily derived from the crop.
Last year this hypothesis also got support from an anatomical study of weedy rice in the USA, by Thurber, Kepler and Caicedo in BMC Plant Biology which shows that the abscission layer which leads to shattering is clearly distinct from non-shattering domesticated rice but also differs from shattering wild rices in terms of its timing in development: it breaks down sooner leading to earlier shattering than in wild rice. This presumably is an useful adapation for beating the farmer to it and getting into the seedbank before the rice harvest. Thurber et al conclude that this points to unidentified regulatory genes that allowed weedy rice, derived from the crop, to reacquire wild-type shattering. (Whether one might be able to tell weedy from wild rice on the physical remains of spikelet bases is another matter, but surely worthy of investigation by an archaeobotanist!). What is more, genetic characterization (Thurber et al 2010 Molecular Ecology) found that these weedy rices all possessed the sh4 mutation that characterizes domesticated non-shattering rices! This points unambiguously to the acquisition of a different novel mutation that allows shattering. A few years ago Londo & Schaal (in Molecular Ecology) did some haplotyping of American weedy rices and found mutliple origins, with haplotypes from japonica, indica and aus rices (as well as some hybridization).
So rice has a proclivity to weediness, as with many other crops, and the wild progenitor per se may be less to blame. Contrast this with crops that have been domesticated from weeds (oat, rye, kodo millet) and we can begin to think about alternative pathways to and from being a weed.
Last year this hypothesis also got support from an anatomical study of weedy rice in the USA, by Thurber, Kepler and Caicedo in BMC Plant Biology which shows that the abscission layer which leads to shattering is clearly distinct from non-shattering domesticated rice but also differs from shattering wild rices in terms of its timing in development: it breaks down sooner leading to earlier shattering than in wild rice. This presumably is an useful adapation for beating the farmer to it and getting into the seedbank before the rice harvest. Thurber et al conclude that this points to unidentified regulatory genes that allowed weedy rice, derived from the crop, to reacquire wild-type shattering. (Whether one might be able to tell weedy from wild rice on the physical remains of spikelet bases is another matter, but surely worthy of investigation by an archaeobotanist!). What is more, genetic characterization (Thurber et al 2010 Molecular Ecology) found that these weedy rices all possessed the sh4 mutation that characterizes domesticated non-shattering rices! This points unambiguously to the acquisition of a different novel mutation that allows shattering. A few years ago Londo & Schaal (in Molecular Ecology) did some haplotyping of American weedy rices and found mutliple origins, with haplotypes from japonica, indica and aus rices (as well as some hybridization).
So rice has a proclivity to weediness, as with many other crops, and the wild progenitor per se may be less to blame. Contrast this with crops that have been domesticated from weeds (oat, rye, kodo millet) and we can begin to think about alternative pathways to and from being a weed.
When there is no blog
No one has time to blog all the time or to blog every new archaeobotanical study that deserves it, or relevant genetic study. Some I have set up some scoop.it pages to stash links to sources and citation of interest when I simply don't have time to blog, or have not gotten a chance to read them. Suggestion of sources are welcome. One scoops page that I have been trialling for a while is one rice origins and culture history, and the other is more general on archaeobotany and domestication. I also do one on Nubian archaeology, since I teach in this area.... By the way, for those wondering the image at the left is a waterlogged Euryale ferox seed from Tianluoshan (Neolithic Zhejiang, China).
Eastern Mediternnanean database back on-line
Simone Riehl's database of Eastern Mediterranean and Near Eastern Plant Remains has been offline for a while due to a server change. But tt is now online again under: www.ademnes.de
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