Category: Genetic diversity

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Invasiveness and extinction revisited

If you’ve been following (listening to?) our tweets ((I never thought I’d ever write that, but time and the social web wait for no-one.)) you might have seen this enigmatic little gem:

Population genetic diversity influences colonization success. K. M. CRAWFORD. Molecular Ecology: http://goo.gl/JFHh

And, possibly, ignored it. It must have registered at some level though, because when I saw Inbreeding bad for invasives too at C.J.A. Bradshaw’s blog Conservationbytes.com I thought, “Hmmn, I wonder if that’s the thing we tweeted”. ((Which gives me the opportunity to remind you that we don’t tweet everything we write about here, nor do we write here about everything we tweet.)) And it was. Bradshaw does a great job of explaining how it is that reduced genetic diversity contributes not only to a population’s risk of extinction, but also to its ability to invade new habitats.

Crawford & Whitney measured greater population-level seedling emergence rates, biomass production, flowering duration and reproduction in high-diversity populations compared to lower-diversity ones. Maintain a high genetic diversity and your invasive species has a much higher potential to colonise a novel environment and spread throughout it.

Of course, this is related to propagule pressure because the more individuals that invade/are introduced the more times, the higher the likelihood that different genomes will be introduced as well.

So far the experimental evidence comes only from Arabidopsis thaliana, the white rat of the plant biologist. But I’d be willing to bet that if you could measure such a thing as invasiveness and persistence for crop varieties, where people, rather than nature, determine how many propagules survive and spread, the ones that are both widespread and long-lasting are also the ones with the most genetic diversity.

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Locating agricultural origins in Mexico and Italy

I know that domestication is not an event, but a process. I know that most crops and livestock were probably domesticated more than once, in more than one area. I know all this, but I’m still a sucker for papers that come up with specific times and places for the origin of agriculture. Papers such as Daniel Zizumbo-Villarreal and Patricia Colunga-GarcíaMarín‘s in the latest GRACE:

Sympatric distribution of the putative wild ancestral populations of maize, beans and squash indicate the extreme northwest Balsas-Jalisco region as a possible locus of domestication.

The paper is a review. It synthesizes a host of paleoecological, archaeobotanical and molecular data. Meanwhile, another paper, this time in the Journal of Archaeological Science, applies matrix mathematics to a somewhat different, though related, problem: the arrival of wheat in Italy. The authors looked at a selection of old emmer landraces from all around Italy stored in the German and ICARDA genebanks. ((The question of why they did not obtain material from an Italian genebank is one that I am loath to explore, for fear of what I might find.)) They developed a matrix of genetic distances among these based on microsatellite data. They then calculated matrices of geographical distances among the landraces based on different putative places of arrival of the crop around the coast of Italy. The two matrices showed the closest correlations for arrival sites located in northern Puglia, the heel of Italy. That corresponds with where the earliest Neolithic sites are found.

Now, I wonder, when will someone apply this method to maize, beans and squash molecular data and test mathematically Zizumbo-Villarreal and Colunga-GarcíaMarín more “qualitative” inferences?

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Patenting systems good for vegetable diversity

Here’s a turn-up for the books. Our friends at the CAS-IP blog link to a couple of papers that examine the influence of intellectual property rights on vegetable diversity. I’m going to come right out and admit that I haven’t read the papers. But like CAS-IP, I’m intrigued by this quote:

More than 16% of all vegetable varieties that have ever been patented were commercially available in 2004.

Or, to put it another way, less than 84% of all vegetable varieties that have ever been patented were no longer available in 2004.

The primary argument for maintaining crop diversity ((I’m not sure that that would be my primary argument, but let that be.)) is based on the need to maintain a safety net of genetic diversity, to have a broad supply of genes available to breeders who can create more productive, weather-hardy, insect resistant, fungus resistant, and better-tasting crops. … If the meaning of diversity is linked to the survival of ancient varieties, then the lessons of the twentieth century are grim. If it refers instead to the multiplicity of present choices available to breeders, then the story is more hopeful.

The crucial part, of course, is how to measure diversity, and how you interpret it. I deliberately snipped out what I consider the money quote from the passage above. Here it is:

We hope our findings stimulate a discussion about the proper measure for that diversity.

Off you go. Discuss away.

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A banana new to science

news_umq_bir_fruit_buerket.jpg Somewhere this morning I read something silly from a conservation whiner that the mainstream media would pay more attention to Paris Hilton taking a pee in South Africa, or 10 murders, than the loss of 10 wild species. I didn’t even bother to bookmark it, so familiar was the sentiment. To redress the balance, here’s an entirely new banana cultivar, heretofore unknown to science, spotted by Luigi on the proMusa website and shared with the world via Twitter. It was collected in Oman in 2003 or 2004 and grown on in Germany. I’m not sure yet what it is good for, although it is drought resistant. And “[t]he authors speculate that the variety, which they named Umq Bi’r, might have reached Oman many centuries ago via Zanzibar, Madagascar or the Comoros”. More interesting than Paris Hilton taking a pee? You bet!