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Can wild relatives survive introgression?

Crops can benefit from the introgression of genes from their wild relatives, but what about the other way around? Is the survival of crop wild relatives jeopardized by the “genetic pollution” caused by hybridization with the cultigen? A paper just out in the Journal of Applied Biology takes an experimental and modeling approach to answering this question ((D. A. P. Hooftman, M. J. De Jong, J. G. B. Oostermejer, H. C. M. Den Nijs. 2007. Modelling the long-term consequences of crop-wild relative hybridization: a case study using four generations of hybrids. Journal of Applied Ecology 44 (5), 1035–1045.)).

The researchers monitored the germination, survival and seed-set of hybrids between wild (Lactuca serriola) and cultivated lettuce (L. sativa). The overall fitness of hybrids was higher than that of the “unpolluted” wild relative in the first couple of generations, but as those hybrids were selfed and backcrossed, their fitness decreased. These data were then entered into a model, to see what would happen over time to a L. serriola population exposed to geneflow from the cultigen. What happens is that the wild relative can indeed be completely displaced by hybrids, but that is not a foregone conclusion, and in any case displacement, if it takes place, will not be as rapid as predicted by previous models which did not take into account the breakdown in heterosis.

So genetic pollution does pose a real threat to crop wild relatives in the field ((The likelihoods of both hybrid occurrence and L. serriola displacement were still at least 60%.)), but perhaps not as great as some have suggested. And in any case we now seem to have a model that can be used to assess the risk of genetic pollution, including by transgenes.

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Scots forget agricultural biodiversity

Scotland has published figures on trends in a set of biodiversity indicators developed by the Scottish Biodiversity Forum. The indicator of “vascular plant diversity” does include consideration of agricultural landscapes: “although not statistically significant, the survey pointed to possible declines among already low numbers of wild plants present” on arable and horticultural land. Otters are doing better, however, which is good. But what about native livestock breeds, crop wild relatives, landraces? There doesn’t seem to be anything about agrobiodiversity in these indicators. Of course. Pity.

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Diverse cropping systems not weedier

I blogged way back in December about a study by David Tilman at the University of Minnesota which showed that “mixtures of native perennial grasses and other flowering plants provide more usable energy per acre than corn grain ethanol or soybean biodiesel and are far better for the environment” (quoted by Mongbay.com). This was actually the latest in a series of long-term experiments by Tilman looking at the connection between diversity and ecosystem function in grasslands (see also a recent paper by Hector et al. in Functional Ecology). This connection has been less investigated in agricultural systems, however. Which is the reason behind a recent paper in the Journal of Applied Ecology from researchers at Michigan State University ((R.G. Smith, K.L. Gross. 2007. Assembly of weed communities along a crop diversity gradient. Journal of Applied Ecology 44 (5), 1046–1056.)).

Continue reading “Diverse cropping systems not weedier”

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Agrobiodiversity 101

This article introduces an ongoing series that will examine the many lesser-known plants and animals that could benefit humanity … if we work to preserve them.

So far, so uncontroversial. The way people play with the “X food supply from Y species” thing intrigues me, as does the “Z edible species” assertion. These numbers have the ring of the catechism about them. But as a summary to the issues, this series may prove worthwhile.

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Rising food prices threaten on-farm biodiversity

Back in the 1990s the European Union, concerned about over-production of poor-quality cereals, introduced set-aside. Farmers were required to not grow food on a percentage of their land, currently 8%, and were paid to do so. The result was an increase in biodiversity; wildflowers, insects, birds, that sort of thing. Now, with rising food prices, there’s a proposal to reduce the area of set-aside to 0%, and conservationists are unhappy.

This is an old argument. Grow more food more intensively and you spare some “wild” habitat. I suppose the question is, how long will high food prices last? Until rain returns to Australia? Or until the world wakes up from its ethanol binge?