Category: Genetic diversity

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Shades of blue, Tokyo style

The Human Flower Project reports on a DIY indigo-dyeing shop in the heart of Tokyo. A fine idea, for all sorts of reasons. It puts people in touch with a natural, plant-based dye and offers us a chance to talk about agricultural biodiversity and even plant biochemistry.

The Human Flower Project’s page shows a photograph of the source of indigo labelled Polygonum tinctorium, also known as Chinese indigo. I fondly remember visiting an indigo demonstration dyer near Toulouse, in France, that sourced the dye from woad, Isatis tinctoria. And then there’s the Asian (or true, sic) indigo, Indigofera tinctoria. Native American tribes apparently used other legumes closely related to true indigo for their blue dyes.

What they all have in common is the process to get the colour. Young leaves are mashed with water and then encouraged to ferment. That results in a greenish sludge. The fabric is immersed in the sludge and then hung up to dry. As the pigments oxidize, they turn blue, and expert dyers can control the shade of blue by adjusting the duration of the oxidizing step, and other factors. (Loads more information here.)

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It struck me that indigo would make a marvellous central topic for one of those the-entire-history-of-the-universe-as-seen-through-a-single-neglected-thing books. There’s revolt and revolution, trade wars, the origins of modern organic chemistry, mercantile colonialism, slavery and rice, and pretty colours. Kew contibuted its model of an indigo factory to the BBC’s history of the world in 100 objects, but the model does not seem to have been the subject of one of those wonderful broadcasts. A pal of mine did a book on madder, another brilliant dye; I couldn’t find anything similar for indigo (although there is plenty of woo). Publishers! I am available.

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Nibbles: Milk-drinking, Diversity and stability, Indian sheep, Development of the African savannah, Teaching rice, Silk, Diverse diet, Huge phallic inflorescences

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The social life of taxonomists

If you have full access to the journal Nature, you’ll be able to read Jonathan Silvertown’s correspondence about a pet project called iSpot. Silvertown says:

Through social networking, the identification process can be made more efficient while simultaneously spreading real taxonomic knowledge. The facility is available to anyone, unlike other technologies that require specialized equipment.

In its first year of operation, the website … helped 6,000 users to identify 25,000 sightings of some 2,500 species, from lichens to birds. The website works by linking experts (including amateur experts) with beginners through a sophisticated reputation system that encourages users to help and learn from each other.

This, Silvertown says, is “social networking on the Internet”. 1

And it is, of a sort. Not the sort that we’ve championed here more than once, most famously in connection with some globetrotting taro. It is good that people can get good identification of things they’ve seen, and been able to photograph. My argument with iSpot is that it perpetuates the dichotomy between nature and agriculture, probably unconsciously, although very directly: “your place to share nature”.

So, while you will find crop wild relatives in there, there is no mention of the fact that that is what they are. You won’t find a single entry for Triticum. And so, while there may be lots of discussions of willow warblers vs chiffchaffs, the essential and fundamental differences between the raw materials of beer and bread go unremarked. And where would all those twitchers be without a sandwich and a pint?

Silvertown clearly knows about and cares about agriculture, and is not afraid to use agricultural examples in his teaching and popular writing. I wish he had extended that to his Citizen Science projects.

And while I’m moaning, where’s the site that will allow anyone anywhere to upload a photograph of a crop direct from a mobile phone and get it identified, preferably to variety level?

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Soil biodiversity helps maintain plant genetic and species diversity

ResearchBlogging.orgAttentive readers of this blog will recall an interesting experiment run by Richard Lankau of UC Davis and others a couple of years back which looked at how genetic diversity can help maintain species diversity in a model ecosystem. There’s now a new paper out by Dr Lankau which investigates in more detail the mechanism behind this. 2

Let’s recap. In the earlier paper, researchers…

…grew monocultures of two genetic variants of an annual plant called black mustard [Brassica nigra], and also a mixture of three species. One of the black mustard varieties produced high levels of a compound called sinigrin, which is toxic to other plants and to beneficial soil micro-organisms, the other produced low levels. The researchers then introduced a “foreign” individual into each of these experimental communities: a low sinigrin plant into the high sinigrin monoculture and the mixture, a high sinigrin plant into the low sinigrin monoculture and the mixture, and a plant of a different species into the monocultures and the mixture. Which would survive? It turned out that the high sinigrin invader only survived in the mixture, while the low sinigrin variety only survived in the high sinigrin monoculture. No one variety was always best, which meant that each could survive somewhere. Remove any one element, whether variety or species, and the system became dominated by a single thing.

In the latest study, Lankau et al.

performed several experiments to determine whether different B. nigra genotypes and their heterospecific competitors cultivated different soil communities, and, in turn, if differences in these communities mediated some or all of the competitive interactions seen in previous field studies.

The answers were: yes, and some. Yes, indeed, the composition of the soil microbial community (bacteria, fungi, arbuscular mychorrizal fungi) was indeed quite different under the different plant communities. But this did not affect the ability of the different mustard genotypes to invade mustard monocultures, for example. In contrast, however, the fact that high sinigrin mustard genotypes competed strongly in heterospecific mixtures was probably due to changes in the soil biota.

The main conclusion of the earlier study was:

Preventing the erosion of genetic diversity within species may require maintaining a diversity of species in a community. At the same time, we may need to focus on protecting high levels of genetic diversity within species in order to maintain diverse communities of species.

We can now add that soil biodiversity can play an important role in maintaining both genetic and species diversity in plant communities by mediating competitive interactions. I’m looking forward to the next installment of this saga.