Meta-analyzing diversity

If you’ve just arrived from Tangled Bank, welcome. And be aware that there’s a follow-up post.

A couple of meta-analyses on the menu today. Devra Jarvis and Bioversity International colleagues, together with numerous co-authors from national programmes around the world, have a paper in PNAS summarizing the results of a 10-year effort to establish the scientific bases of on-farm conservation of agrobiodiversity.

Varietal diversity data on 27 crops grown on 64,000 ha by 2,041 households in 26 communities in 8 countries on 5 continents were pulled together in a stunning feat of synthesis. Are any generalizations possible from such a massive dataset? Well, perhaps surprisingly, yes. Let me pick out the highlights:

  1. Households growing traditional varieties generally grow more than one (1.38-4.25).
  2. Households within a community tend to grow somewhat different sets of traditional varieties.
  3. Larger fields generally have more traditional varieties, but smaller fields tend to be more different in varietal composition.

There’s much more to this rich analysis than that, but the take-home message can be pretty easily stated: crop genetic diversity can still be found on-farm because even neighbouring families choose to grow different traditional varieties, and generally more than one. Especially families tending smaller fields, who will presumably be poorer and living in more marginal conditions. The conoscenti will recognize a familiar meta-narrative, but it is good to have solid data from a wide range of crops and from all over the world.

The next paper I want to talk about looked at genetic diversity in wild clonal species as it relates to their breeding system.

Summarizing 72 genetic diversity studies, including of a couple of crop relatives, the authors found that populations of self-incompatible clonal species tended to have fewer genotypes, more unequally distributed (i.e., with a few dominant clones), than populations of self-compatible clonal species. It would be interesting to see if this relationship is also present in vegetatively propagated crops. I don’t think the previous dataset would help with that, however. Only two clonal crops were included in the on-farm analysis, cassava and taro. Interestingly, they had the highest average levels of community-level varietal richness (33) compared to seed-propagated species.

Classifying conservation actions

An article in PLoS Biology recently suggested that IUCN should change the classification system it uses for protected areas (PAs). Currently reflecting management intent (e.g. “National Park: managed mainly for ecosystem protection and recreation”), the idea would be for the new categories to rather “be based on the quality and quantity of the contribution of each PA to conservation of biodiversity (and associated sociocultural values).” So: actual result, rather than intent; and “what ” and “how much” rather than “how.” Seems like a pretty good idea. And it also seems like the concept could be applied not just to protected areas, but to conservation actions in general. That would spell the doom of the tired old in situ/ex situ dichotomy. Not a minute too soon, as far as I’m concerned.

African protected areas surveyed

The EU-funded “Assessment of African Protected Areas” is out:

The purpose of the work is to provide to decision makers a regularly updated tool to assess the state of Africa PAs and to prioritize them according to biodiversity values and threats so as to support decision making and fund allocation processes.

It is great stuff: detailed, standardized descriptions of the importance of — and threats faced by — each protected area in Africa. I wonder if something similar will ever be done for agricultural biodiversity. An interesting first step might be to mash these results with those of the recent survey of crop wild relatives in protected areas. Unfortunately, the agrobiodiversity and protected areas communities hardly ever speak to each other.

Weekly helping of potatoes

The Economist seems to have a thing about potatoes this week. There’s a story about how Peru is trying to cash in on its spud heritage. (Note to editor: the olluco is not a type of potato.) There’s a book review, of John Reader’s Propitious Esculent. And there’s even an editorial explaining how the humble tuber is at the root — as it were — of globalization. The International Year of the Potato cannot be over too quickly.