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Parasites push promiscuity

Many hermaphrodite plants (and some animals) — including many crops — have what is called a mixed mating reproductive strategy. That means they reproduce by both self- and cross-fertilization, with important consequences for the amount and structure of their genetic variation. The prevalence of mixed mating systems is surprising because inbreeding depression should work to get rid of self-fertilization, resulting in “pure strategies of either outcrossing or selfing.” Now a new study suggests that its natural enemies — pests, parasites, herbivores, etc. — may have a strong effect on the evolution of a plant’s mating systems:

For example, enemies may alter the availability of mates in a population, which may have direct consequences for victim mating system evolution. Enemies may also influence the expression of traits that are important for mating system evolution, thereby improving the evolutionary stability of mixed mating as a reproductive system.

Thus the dynamics of the interactions between a species and the biodiversity that surrounds it can counter the effects of inbreeding depression and lead to the stability of an otherwise doomed evolutionary strategy. I wonder how important this has been in the evolution of agrobiodiversity. After all, concentrating plants in dense near-monocultures like agriculture does is a boon to natural enemies.

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News from the front: Belize

As far as I know, it has more species of trees, shrubs, bushes, herbs, and grasses than any domestic garden on Earth: 318 species of flowering plants, 250 of which are native to Belize. That’s about 15 percent of the indigenous floristic diversity of the whole country, more species of native plants than live in the forest that surrounds it. Every plant is here for a purpose, used as medicine, food, thatch, fiber, because it attracts butterflies, birds, and mammals, or just because of its beauty.

The garden is Masewal, in western Belize, and the words are from an article in Orion magazine that describes this astonishing place. The vision of one man, who sought to reclaim some of his Mayan heritage and has been doing so for 31 years, using the garden as store-house, teaching aid and demonstration plot. Fascinating.

Belize was my first experience of a tropical forest and I remember the giddiness of it. I wrote something about it back then; I wonder whether I can dig it out.

via Metafilter.

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Agriculture important, World Bank discovers

The World Bank is suddenly all concerned about agriculture. Within a few days there’s the result of an independent evaluation of its assistance to sub-Saharan Africa, and the latest World Development Report, which focuses on agriculture for development. The NY Times has an article on the African report:

At a time of growing debate about how to combat hunger in Africa, the evaluation team recommended that the bank, the single largest donor for African agriculture, concentrate on helping farmers get the basics they need to grow and market more food: fertilizer, seeds, water, credit, roads.

Ah, seeds. If only it were that easy. The World Development Report 2008 actually refers to the spread of improved varieties as “slow magic” (p. 159, chapter 7), pointing out that crop improvement “has been enormously successful, but not everywhere.” Then, on page 259, in a discussion of the “global agenda for the 21st century,” the money quote:

Conserving genetic resources for future food security. Genetic resources and seeds have been the basis for some of the most successful agricultural interventions to promote growth and reduce poverty (chapter 7). Conserving the world’s rich heritage of crop and animal genetic diversity is essential to future global food security. Gene banks and in situ resources that provide fair access to all countries and equitably share the benefits are a global public good that requires global collective action.

Chapter 8, on Making Agricultural Systems more Environmentally Sustainable, should also make for interesting reading.

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Mutant teff

Sometimes a crop just doesn’t have the genes for it, as a good friend of mine who dabbled in taro breeding used to say. So then you have to try something else. “Zerihun Tadele is using the latest biotechnological methods to produce dwarf tef lines in order to prevent lodging, which causes significant yield losses.” The technique involved is TILLING (Targeting Induced Local Lesions IN Genomes), an automated methods for inducing, and then detecting, potentially useful point mutations. But is there really no short(ish) teff variety among the 4743 accessions in the genebank of Ethiopia’s Institute of Biodiversity Conservation? By the way, IBC has just won the Sultan Qaboos Environmental Preservation Prize. Congratulations!