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Tom Coburn: Iraq war “probably a mistake”

This news is probably a week old, but I still think it’s worth noting.  On Thursday the Tulsa World reported:

U.S. Sen. Tom Coburn’s comment that going to war in Iraq was “probably a mistake” represents a significant departure from where the Oklahoma Republican started out on the 5-year-old conflict.

Coburn’s comment came at the beginning of remarks at a weekend town hall meeting in Muskogee.

“I will tell you personally that I think it was probably a mistake going to Iraq,” said the freshman senator, who made it clear he did not believe the U.S. could withdraw but had to stay. 

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Ants

When I was a child I read a book about ants – about one ant in particular, who was born in a colony, tends to one of her sisters before her nuptial flight, gets swept away from the colony is a flood, and finds herself alone.  She discovers a new colony, but the ants reject her because she doesn’t have the smell of the colony.  She finds a nearby abandoned tunnel and lives there, just to be near other ants.  And then one day, she runs into an ant from the colony and is welcomed – living nearby for so long, she has picked up the scent of the colony.  She is happy, and joins the colony where she eventually meets the queen, who it turns out is the sister she tended to just before her nuptial flight.

I learned so much about ants from that book – about their colony organisation, about the fact that workers are all female, about the existence of male and female alates who are winged and go on one nuptial flight were they mate before shedding their wings (in the case of females) or dying (in the case of males).  I learned that ants recognise colony members by smell.  What I learned from a children’s book was enough to make me better informed about ants than many a zoology gradate student.

I wish I had any idea what that book was or who wrote it.

Bt cotton and the evolution of resistance

Over the last decade, genetically modified crops have become widespread in agriculture. One of the more successful of these are Bt crops – transgenic plants that express genes derived from Bacillus thuringensis. These genes allow the plants to produce toxins which specifically affect certain groups of insects. Since these plants do not need to be sprayed, and since the toxins are relatively specific, the environmental effects appear to be lower than conventional agriculture.

However, Bt toxins face the same problem that other pesticides face – the evolution of resistance in target insects. The selective pressure of a compound in your food that kills you (unless you have a resistance gene) is huge. The more widely a Bt crop is planted, the greater the selective pressure. And unlike pesticides, to which a pest is only exposed periodically, Bt toxins will (presumably) be produced by the plants on a continuous basis. Since lab studies had showed that pest species possessed genetic variation in their resistance to Bt toxins (including this 1998 EPA study), the question is more one of how quickly resistance would evolve, rather than if resistance would evolve.

One strategy to slow the evolution of resistance is to plant areas of non-Bt plants near to the fields of Bt crops. These would serve as refuges for populations of non-resistant insects. In principle it should work great – as long as the resistance genes are recessive. If you plant a large area of crops that are toxic to their pests, what happens is that most of the pest population will be wiped out. A few will have some resistance (after all, Bt toxins exist in nature – Bacillus thuringensis occurs in nature, and is likely to have interacted with the pest species in its evolutionary history). Since all the individuals lacking resistance genes would have been knocked out of the population, resistant individuals would mate with one-another. As a result, each subsequent generation should be more resistant than the previous. However, if you provide a refuge of non-Bt crops, most of the individuals in the next generation would come from that part of the population.

If resistance to Bt toxin is a recessive trait, an individual needs to inherit the gene from both parents in order to be resistant. If the population is only made up of those who survived exposure to the toxin, they will mate with one-another, and their offspring will inherit the trait. On the other hand, if the population is dominated by susceptible individuals (those that fed on the non-Bt crop) then the survivors’ genes will be diluted in a much larger population. On the other hand, if resistance is a dominant trait, providing a refuge won’t work. If the trait is dominant, it doesn’t matter who the survivors mate with – they will still be able to pass their resistance on to their offspring.

ResearchBlogging.orgIn an article published in Nature Biotechnology, Bruce Tabashnik and colleagues looked at the actual pattern of evolution of resistance to Bt toxin Cry1Ac in cotton over a 10-year period. They used studies conducted in Australia, China, Spain and the United States focusing on six pest species: Helicoverpa armigera, H. zea, Heliothis virescens, Ostrinia nubilalis, Pectinophora gossypiella and Sesamia nonagrioides. They found that in only one of these species – H. zea – had the frequency of resistance genes increased substantially.

One explanation for the evolution of resistance in H. zea is the observation that resistance to the Bt toxin Cry1Ac appears to be the dominant trait. This greatly reduces the effectiveness of refuges, since the resistance genes aren’t diluted out as effectively as they would be if they were recessive.

Helicoverpa zea has not evolved resistance in all areas – populations in Arkansas and Mississippi had done so, but those in North Carolina had not. This was attributed to differences in the effective refuge sizes:

Gustafson et al. [2006] meticulously estimated that the effective refuge abundance during each of three generations when H. zea fed on cotton was 39% in Arkansas and Mississippi and 82% in North Carolina. With these refuge sizes, H. zea is projected to evolve resistance after 9 years in Arkansas and Mississippi. By contrast, in North Carolina, resistance evolution should take >20 years, with the expected resistance allele frequency still <0.005 after 10 years.

However, the evolution of resistance has not led to any crop failures. Even where resistance has evolved, most populations are not resistant, and even among resistant strains “Cry1Ac in Bt cotton still caused 48–60% larval mortality”. In addition, spraying is still used to combat large pest outbreaks, and “pyramided” transgenic plants which contain both Cry1Ac and a second Bt toxin, Cry2Ab have been introduced. Resistance to one Bt toxin does not convey resistance to the other, so it’s far more difficult for pests to evolve resistance to plants producing both toxins.

Tabashnik, B.E., Gassmann, A.J., Crowder, D.W., Carriére, Y. (2008). Insect resistance to Bt crops: evidence versus theory. Nature Biotechnology, 26(2), 199-202. DOI: 10.1038/nbt1382

Unfolding scandal

Drip, drip, drip…

I would like to thank the Academy,…

In recognition for my singular achievements* in blogging, that most distinguished authority on all things bloggy, Mike O’Risal of Hyphoid Logic has named me to Knights of the Hyphoid Logic Realm and awarded me the highly prestigious “E for Excellence” award.

One of the benefits of having been bestowed this honour is the ability to bestow it on ten others (but since Mike only used 9 of his 10 slots, I’m stealing one of his). Oh the power I have been given! Must…not…let…it…go…to…my…head.

How do I pick ten eleven worthy blogs? Ten Eleven that are at least as good as mine. At least that’s easy – my achievement was showing up. Now who else shall I add to our distinguished fellowship?

  1. Exploring Our Matrix: the newly tenured Assistant Professor Dr. James F. McGrath, Ph.D., Esq. is most deserving of an award for excellence; if for nothing else than for this quote: If you … think that the majority of scientists are wrong and you (perhaps together with a small minority) are right, then I congratulate you: you are a crackpot!
  2. Genomicron: T. Ryan Gregory is most deserving of an award for excellence; his blog is a place you can really learn something; he has three blogs and still is a scarily productive kick-ass scientist.
  3. NewPagesBlog: Denise Hill** is most deserving of an award for excellence; her blog is would be an amazing resource if only I could read (and she’s the best writer I know in real life).
  4. Greg Laden’s Blog: Greg Laden is most deserving of an award for excellence; although his blog has been assimilated into the ScienceBlorg Collective, he’s still an excellent blogger, and anyway, I was reading his blog long before its assimilation; Greg is the hardest working blogger in the blogosphere, posting a minimum of 438.2 posts per day.
  5. Monkey Trials: Scott Hatfield is most deserving of an award for excellence; although Scott deserves an award for a number of other things (like teaching chemistry after the administrators confiscated all his chemicals or being the only Christian to have won PZ’s admiration), this one is for the quality of his blog posts.
  6. Northstate Science: Christopher O’Brien is most deserving of an award for excellence; he is just restarting his blog after a hiatus and switch from blogger to wordpress but is off to a really good start.
  7. Agricultural Biodiversity Weblog: Luigi Guarino and Jeremy Cherfas are most deserving of an award for excellence; this blog has an amazing amount of information, about a topic that is vitally important to everyone who eats, but gets almost no attention in either the press or the blogosphere.
  8. The DIVINE Afflatus: Mark is most deserving of an award for excellence; his blog is smart, well written and well worth reading; unfortunately, there’s just too little of it; in the hope that he will blog more often.
  9. Thoughts in a Haystack: John Pieret is most deserving of an award for excellence; his posts are lengthy, intelligent, and have a lot to think about in them; consequently, they tend to go over my head.
  10. The Manicou Report: Mani is most deserving of an award for excellence; Mani gets to the point on issues that really get under your skin (or rather, things that feel like a police boots on yuh corn).
  11. Bug Girl’s Blog: Bug Girl is most deserving of an award for excellence; Bug Girl just rocks; most of her posts are eye-openers.

There are more people who deserve mention, but I’m kinda limited to 10. Obviously, if Mike hadn’t done the honour, ERV, the Austringer and Science After Sunclipse would probably be on my list. Apart from Greg Laden, I decided to steer clear of the big boys like the people on ScienceBlogs, Larry Moran of Sandwalk and the people who are really out of my league – Markos of Daily Kos, Josh Marshall of Talking Points Memo or Barbara O’Brien of Mahablog.

*or rather, my single achievement in blogging – being the only Trini Botanist in the blogosphere.
**I must declare a conflict of interest in this award: about twice a year Denise puts us up in her guest bedroom, feeds us and buys us beer.