Category: Genetic diversity

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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”. ((And yes, there is something delicious about promoting the virtues of the social networking behind a paywall.))

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. ((Lankau, R., Wheeler, E., Bennett, A., & Strauss, S. (2010). Plant-soil feedbacks contribute to an intransitive competitive network that promotes both genetic and species diversity Journal of Ecology DOI: 10.1111/j.1365-2745.2010.01736.x))

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.

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Evergreen agriculture: crops and trees

What if growing maize under trees – really under trees, under the canopy – improved yields by 280 per cent? It did in Malawi. Even if this practice doesn’t translate well to developed world agriculture, the principles of Evergreen Agriculture can.

Matt at Muddy Green takes a look at Evergreen agriculture: crops and trees, a different kind of agroforestry. I’ve always imagined that agroforestry was more about alley cropping or the like, but this idea of planting under the trees seems rather interesting and rather successful, at least in places where the trees are bare during another crop’s growing season.

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The revenge of history

Three papers today which look into the role of history in determining patterns of diversity, at the species and genetic level. I don’t have much time today, so descriptions will have to be quick and dirty for now.

In Molecular Ecology, Hoban et al. used microsatellites to genotype 29 populations of Juglans cinerea from throughout the eastern US. ((HOBAN, S., BORKOWSKI, D., BROSI, S., McCLEARY, T., THOMPSON, L., McLACHLAN, J., PEREIRA, M., SCHLARBAUM, S., & ROMERO-SEVERSON, J. (2010). Range-wide distribution of genetic diversity in the North American tree Juglans cinerea: a product of range shifts, not ecological marginality or recent population decline Molecular Ecology DOI: 10.1111/j.1365-294X.2010.04834.x)) They wanted to know whether the observed pattern of genetic diversity was best explained by the spread of the species from refugia after the last glaciation, by its recent dramatic decline due to a fungal pathogen, or by a core-vs-periphery effect. It turned out to be the first of these. One of the consequences is that southern populations are the most diverse, and should be the ones to be targeted for ex situ conservation in the face of the depredations of the fungus.

Meanwhile, over at the Journal of Applied Ecology, Reitalu et al. looked at species diversity in Swedish grasslands in relation to various aspects of management. ((Reitalu, T., Johansson, L., Sykes, M., Hall, K., & Prentice, H. (2010). History matters: village distances, grazing and grassland species diversity Journal of Applied Ecology DOI: 10.1111/j.1365-2664.2010.01875.x)) They found that distance to the nearest historical village was an excellent predictor of grassland diversity, integrating various management variables. Diversity peaked at 1-1.5 km from the nearest village, and declined thereafter with distance. This finding could be used to prioritize grasslands for conservation, and to devise appropriate management programmes, which should involve moderate grazing pressure.

Finally, again in the Journal of Applied Ecology, González-Varo et al. describe a somewhat retro study on the Mediterranean Shrub Myrtus communis in SW Spain using isozymes. ((González-Varo, J., Albaladejo, R., Aparicio, A., & Arroyo, J. (2010). Linking genetic diversity, mating patterns and progeny performance in fragmented populations of a Mediterranean shrub Journal of Applied Ecology DOI: 10.1111/j.1365-2664.2010.01879.x)) Working not only on the actual natural populations but also on progenies, they wanted to know the relative importance of the past and the present effects of fragmentation of populations on fitness. The past effects were represented by the genetic diversity of populations, the present effects by outcrossing rates. In contrast to the previous two papers, they found that the present is a better guide to conservation that the past. It was outcrossing rates that had the strongest effect on the fitness of progenies. The recommendation is for honeybee hives to be controlled in the vicinity of these populations, to foster a diverse assemblage of local pollinators, and thus increased outcrossing.

Great to see very clear conservation recommendations being made in all cases, solidly based on the results. It is not always so.