February 15, 2014

Darwin Day 2014 -- North Dakota State University takes the cake


Wow! I can't decide whether I'm more impressed by:

* the guy in the pickup truck who saw us carrying the cutout photo of young Darwin and asked "Is that [W.D.] Hamilton?"
* the evolution-themed parody of John Lennon's "Revolution", composed and performed by a dean who, like God, may have "an inordinate fondness for Beatles".
* the wildly popular herpetology petting zoo (I should have taken a photo), or
* the "Hall of Biodiversity" (a wide range of interesting materials from campus natural-history collections, showing butterfly mimicry, comparing mammoth with mastodon teeth, using C4 photosynthesis as an example of parallel evolution, etc.) set up in the student center next to the auditorium where I gave my talk on "Darwinian Agriculture: Evolutionary Tradeoffs as Opportunities" and the lobby area (shown) where they sold Darwin-Day tee shirts and served cake.

But the cake I made for Darwin's 200th birthday was better.

October 4, 2013

Domestication effects on stomata, and kin competition in plants

There's probably some scientific connection between the two topics in this week's title, but I'm combining them because Ruben Milla has worked on both.

He and his colleagues just published a paper on "Shifts in stomatal traits following the domestication of plant species", comparing lots of crops with their wild relatives. Total abundance of stomata (leaf pores that let CO2 in and water vapor out) doesn't show a consistent increase or decrease with domestication, but there's a tendency for fewer of them to be on the lower side of the leaf.

In adding this paper to my database, I rediscovered one of Milla's earlier papers, on kin interactions in plants. Even though I'd blogged about it when it came out, I'd forgotten nearly all the details. I may be trying, unsuccessfully, to follow too many topics. Since some readers may have missed my earlier post, and since we are celebrating the 50th anniversary of Hamilton's and Maynard Smith's papers on inclusive fitness and kin selection, I am copying my 2009 post below.


This week I will discuss two papers, both dealing with plants and competition, in the context of genetic relatedness that might be expected to moderate competition:
"Growing with siblings: a common ground for cooperation or for fiercer competition among plants?" by Ruben Milla and colleagues (Proceedings of the Royal Society), and
"Do plant parts compete for resources? An evolutionary viewpoint" by Victor Sadras and me (New Phytologist).

Earlier I discussed a paper by Susan Dudley and Amanda File showing that some plants grow less root when interacting with related than with unrelated neighbors. Spending less resources on roots could have freed resources for more seed production, but they didn't measure that. Now Milla and colleagues have.
They grow three lupine plants per pot, using either three seeds from the same plant, three seeds from different plants in the same area, or three seeds from different parts of Spain, and measured various aspects of plant growth and reproduction. In contrast to what I might have expected from Dudley and File's work, plants surrounded by siblings produced no more seeds than plants surrounded by strangers. In fact, one of their measures showed significantly more seed production from plants growing with plants from other regions.

They suggest two possible explanations. First, there was some tendency for plants to grow taller when growing with close kin, perhaps because they all germinated at the same time and thereby triggered an "arms race" to get above each other. The resulting over-investment in stem could leave less resources for seed production. Their other explanation is almost the opposite. What if closely related plants invest less in root, as Dudley and File found, and (under the conditions of Milla's experiment) this resulted in too little root for optimal uptake of water and nutrients?

When wild plants are grown in pots in a greenhouse, they may not allocate resources optimally, nor respond normally to environmental cues, including cues about the relatedness of their neighbors. But if hypothetical cooperation among closely related plants is weak enough to be undermined (even reversed) by growth conditions, the tendency to cooperate can't be very strong.

I discussed a paper by Victor Sadras in one of my first posts in This Week in Evolution, so I was intrigued when he invited me to collaborate on a paper reviewing the idea of "competition" among parts of the same plant. We argue that mechanisms that look like within-plant competition often act to maximize overall plant reproduction. A branch shaded by another branch may die, but this is more like suicide than murder. We know this because the same degree of shading isn't lethal when the whole tree is shaded equally. When only one branch is shaded, however, it can increase the frequency of its genes in the next generation by sending its nitrogen to better-lit branches, where the photosynthesis rate per unit nitrogen is greater. Seeds produced on those branches carry the same genes as those that the shaded branch could have produced itself. Selfish genes lead to unselfish branches.

Competition among seeds on the same plant is a different story. These seeds may have different fathers, whose pollen contained competing versions of various genes. Gene variants that help a seed take more than its share of resources from the mother plant will tend to increase over generations, unless countered. But mother plants have various counter-measures that tend to equalize resources among seeds. (This contrasts with birds that can only bring enough food to feed one chick. They may lay two eggs, but then let the stronger chick kill the weaker.)

We suggested that natural selection for equalizing resources among seeds has often set limits on how much seeds can grow, even when conditions turn out to be unusually favorable during seed-fill. This tradeoff may have been worth it for genetically diverse wild plants. In modern agriculture, however, whole fields may be almost identical, genetically. We might therefore be able to eliminate some of these ancestral seed-balancing mechanisms, letting seeds grow more when conditions are good.

Such tradeoffs between past natural selection and present human goals are a major theme of my forthcoming book, "Darwinian Agriculture: where does Nature's wisdom lie?"

September 6, 2013

My upcoming talks

I don't think my talk at Ringberg Castle next week is open to the public, but these departmental seminars probably are:

Sept. 27, Kellogg Biological Station, Michigan
Oct. 4, St. Thomas University, Minnesota
Oct. 11, Oberlin College, Ohio
Oct. 30, Horticulture Department, University of Minnesota
Nov. 21, Iowa State University

Talk titles are mostly something like:
"Darwinian agriculture: evolutionary tradeoffs as opportunities"

August 30, 2013

Charles Darwin and Casuarina

WorldCat, which lists the holdings of libraries all over the world, is now claiming that several hundred libraries have my book, Darwinian Agriculture. Many of these appear to be "electronic access", which won't accelerate the availability of the paperback, but that still seems like a lot.

Among the libraries on the current list are those at Epic Bible College -- what a great name! -- and at Charles Darwin University. Another great name, and it gets better. It's near Darwin, Australia, but actually located in the town of Casuarina, which is named for one of my favorite trees. Casuarina is:

* A nitrogen fixer that isn't a legume.
* A flowering plant that looks like a conifer.
* So salt-tolerant I've seen it growing a few meters from the ocean, on Heron Island.

July 19, 2013

Weed evolution in the New York Times

Carl Zimmer, author of several evolution-themed books and an interesting blog, published an article on weed evolution in Tuesday's New York Times. He used one of my favorite examples of rapid evolution of complex traits (flooding tolerance and crop mimicry in Echinochloa barnyardgrass/watergrass in <1000 years) to make the point that evolution of herbicide resistance (a much-simpler trait) in only a few years shouldn't have been a surprise.
(Left) Under selection pressure imposed by farmers with hoes, Echinochloa watergrass evolved to resemble rice more than it resembles its own recent ancestor, barnyardgrass (Barrett, 1983). I discussed this example near the end of this lecture at the International Rice Research Institute.

Glyphosate-resistant weeds are becoming increasingly common, just before the expiration of Monsanto's patent on Roundup-Ready soybeans. What does the US Constitution say about patents?

"The Congress shall have Power To...promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries...."
If the original intent was to give inventors short-term monopolies, in exchange for long-term benefits to society, should the duration of patent protection be shorter for inventions whose useful life is likely to be limited by evolution? For example, 17 years with a really good resistance-management plan, 5 years with no resistance-management plan.... Of course, the Patent Office might need to hire an evolutionary biologist or two.

I agree with the statement from David Mortensen that adding another resistance gene to glyphosate-resistant crops, and spraying with both herbicides, will be only "a short-lived solution," although it might last long enough to be worth patenting. If they had put two different herbicide-resistant genes into soybean from the start, and if evolution of resistance requires two or more independent mutations -- this isn't always true -- and if farmers growing that herbicide-resistant crop were somehow required to use both herbicides (so that mutants resistant to just one of the herbicides wouldn't have increased in frequency), evolution of resistance might have taken much longer.

Zimnmer quoted me and mentioned my book on Darwinian Agriculture, depleting Amazon's stock, though they still have a few copies left. You could try your favorite independent bookstore or library.

June 14, 2013

Recent and upcoming talks

Last week I was at Mexico's National Laboratory of Genomics for Biodiversiity (Langebio), giving a keynote talk on Darwinian Agriculture and learning about the diverse research program there, from microbial communities to manipulation of ant "bodyguards" by Acacia plants to using yeast to answer fundamental evolutionary questions.

On Sunday, June 23, I'll be giving a talk on Darwinian Agriculture, as part of the "Evolution Out of Bounds" symposium at the Evolution 2013 meeting, in Snowbird, Utah. These annual evolution meetings are usually really interesting, as I've discussed previously, and other talks in the symposium range from evolution of disease to evolving robots. Those interested in our evolution-of-multicellularity research should look for the talk by Kristin Jacobsen on Sunday afternoon and the poster presentation by Jenn Pentz Monday evening.

April 17, 2013

High-school student undermines our "famine-food longevity" hypothesis, maybe

Back in 2009, I suggested that, to the extent that organic foods provide greater health benefits, this might be due to tradeoffs with reproduction. See my original post for a more-detailed explanation. Since then, I've seen at least one paper on a diet that increases both longevity and reproduction in some species, but there were no data on the timing of reproduction, which is key to our hypothesis.

This week, however, high school student Ria Chhabra and colleagues published a paper in PLoS One reporting both greater longevity and increased egg-laying at all ages, in fruit flies fed various organic foods. It's not inconceivable that some conventionally-grown produce could be so poor, nutritionally, that it would reduce both lifespan and reproduction. But their data seem inconsistent with our hypothesis that organic-vs-conventional differences were mainly differences in toxins (synthetic in conventional, natural in organic) and that natural toxins mainly acted as environmental cues, switching physiology towards longevity at the expense of reproduction.

I'd like to see this experiment repeated by a different lab, however, before drawing firm conclusions. There are a couple of strange things in their data. First, as noted in the paper, survival curves for Drosophila are usually sigmoidal, whereas theirs are more linear. Also, their peak egg-laying rate was reportedly at an age of 1 day. Other studies I've seen show essentially no egg-laying that early, with peaks at day 5 or so. See this paper or this open-access one.

March 29, 2013

Persistent polymorphisms, enhancing mutation, new fossils, cooperation & conservation

All five of my Darwinian Agriculture lectures at the International Rice Research Institute are now available on YouTube.

Here are some interesting papers published this week.

Multiple Instances of Ancient Balancing Selection Shared Between Humans and Chimpanzees " In addition to the major histocompatibility complex, we identified 125 regions in which the same haplotypes are segregating in the two species [neither version has displaced the other in either species in 6 million years], all but two of which are noncoding [i.e., they probably control other genes rather than coding for a protein]." The most likely explanation for such prolonged co-existence is that individuals with less-common alleles may be resistant to pathogens that have evolved to attack those with more-common alleles.

Accelerated gene evolution through replication-transcription conflicts" "We propose that bacteria, and potentially other organisms, promote faster evolution of specific genes through orientation-dependent encounters between DNA replication and transcription."

Palaeontology: Tubular worms from the Burgess Shale"

Preservation of ovarian follicles reveals early evolution of avian reproductive behaviour"

Both information and social cohesion determine collective decisions in animal groups

Governance regime and location influence avoided deforestation success of protected areas in the Brazilian Amazon

Wild Pollinators Enhance Fruit Set of Crops Regardless of Honey Bee Abundance

March 15, 2013

This week's picks

I'm off to the International Rice Research Institute to give a series of five lectures on Darwinian Agriculture. Here are some papers that look interesting this week.

Adaptive Evolution of Multiple Traits Through Multiple Mutations at a Single Gene
Hind Wings in Basal Birds and the Evolution of Leg Feathers
Lifespan of neurons is uncoupled from organismal lifespan
Naturally occurring allele diversity allows potato cultivation in northern latitudes"
Water-controlled wealth of nations

October 18, 2012

A new blog, focused on Darwinian Agriculture

I'm not sure a blog titled This Week in Evolution should have as much focus on agriculture as my recent posts. So I'm starting a new blog, Darwinian Agriculture. Updates, corrections, and discussion of my recently published book by that title will be a major focus, but I hope to include other relevant topics as well. This Week in Evolution will continue to cover a wider range of evolutionary topics, though I may neglect it when I don't have time for both blogs.

October 8, 2012

Darwinian Agriculture reviewed in Science

Allison Snow, whose publications have included some of the best work on gene flow from transgenic crops to weeds, has reviewed Darwinian Agriculture in the journal, Science. Like an earlier reviewer, she noted that I can sometimes be repetitive, but the review was very positive overall. That may explain why Amazon's listing suddenly went from "in stock" to "usually ships within 1 to 3 weeks." You can also order from your local bookstore, Barnes & Noble, or directly from Princeton University Press, whose latest mailing offers a discount.

See also the two-part review by Jeremy Cherfas at the Agricultural Biodiversity Weblog. And if, after reading the book, you agree with Professor Snow that "the book is perfect for discussion-based seminar courses", I may be able to help.