About "This Week in Evolution" and R. Ford Denison
"Can you tell me, in lay language, what makes this achievement significant?"
"I can try", said Denison, cautiously.
-- The Gods Themselves (Asimov)
Ford Denison explains why eating more kale and less meat may trigger physiological changes that sacrifice some potential reproduction but increase longevity (Ratcliff et al., 2009).
About this blog:
Time permitting, I discuss one scientific journal article per week, presenting new data on past evolution or ongoing evolution. My interests in the evolution of cooperation and in agriculture make me include more papers on microbes and plants than some other blogs with an evolutionary focus. I occasionally discuss other topics.
You know how evolution-denialists sometimes claim that they "used to believe in evolution", as if one person's changed opinion trumped the thousands of scientific articles on evolution published each year? For what it's worth, I didn't start as an evolutionary biologist. I earned a PhD in crop science from Cornell in 1983 and was a US Department of Agriculture researcher for several years, before becoming a professor of agronomy at UC Davis in 1993. There, I taught crop ecology, directed a major field experiment on agricultural sustainability (LTRAS), and did research on cover crops that get nitrogen from symbiotic rhizobium bacteria in their root nodules.
My interest in evolutionary biology developed gradually. I wanted my teaching to explain as many facts as possible, using a framework of universal principles, rather than jumping randomly from one fact to another. The universal principles that explained the most crop-ecology-related facts turned out to be conservation of energy, conservation of matter for each chemical element, and evolution by natural selection. The Selfish Gene, by Richard Dawkins, helped clarify my thinking and introduced me to the work of George Williams, John Maynard Smith and especially Bill Hamilton on the evolution of cooperation and, more recently, aging.
Their evolutionary ideas spread to my research, as I tried to answer a question few people had even asked: why do rhizobia invest their resources in taking up nitrogen from the atmosphere and giving it to their host plants, rather than using those resources for their own reproduction? Our 2003 paper in Nature, showing that soybean plants impose fitness-reducing sanctions on rhizobia that fail to fix nitrogen answered that question (although we are still working out some details), and is probably my best-known contribution to science, so far. But our less-cited paper on Darwinian Agriculture, also published in 2003, has generated more speaking invitations and a book contract with Princeton University Press.
In 2005, I took early retirement from UC Davis and a grant-supported adjunct position at the University of Minnesota, in order to live with my horticultural-scientist wife, after many years working in different cities. Here, I have been collaborating with Mike Sadowsky on legume-rhizobia symbiosis and with Mike Travisano on experimental evolution of multicellularity, a project he initiated with Will Ratcliff, who did his PhD with me. I am also trying to develop an experimental system to test our explanation for why certain stresses increase longevity. I provide occasional advice to groups concerned with food security and agricultural sustainability. As long as the National Science Foundation keeps giving me grants, life is good.
R. Ford Denison
Favorite publications through 2011 :
(Google Scholar maintains an up-to-date list, with citations and links, here.
Ratcliff,W.C., R.F. Denison. 2011. Alternative actions for antibiotics. Science 332:547-548.
Denison, R.F., E.T. Kiers. 2011. Life histories of symbiotic rhizobia and mycorrhizal fungi. Current Biology 21:R775-R785.
Oono, R., C.G. Anderson, R.F. Denison. 2011. Failure to fix nitrogen (N2) by nonreproductive symbiotic rhizobia triggers host sanctions that reduce fitness of their reproductive clonemates. Proceedings of the Royal Society B 278:2698-2703.
Denison, R.F. 2011. Past evolutionary tradeoffs represent opportunities for crop genetic improvement and increased human lifespan. Evolutionary Applications 4:216-214.
Ratcliff, W.C., R.F. Denison. 2010. Individual-level bet hedging in the bacterium Sinorhizobium meliloti. Current Biology 20:1740-1744.
Oono,R., R.F. Denison. 2010. Comparing symbiotic efficiency between swollen versus nonswollen rhizobial bacteroids. Plant Physiology 154:1541-1548.
Denison, R.F., J.M. Fedders, B.L. Harter. 2010. Individual fitness versus whole-crop photosynthesis: solar tracking tradeoffs in alfalfa. Evolutionary Applic. 3:466-472.
Oono,R., I. Schmitt, J.I. Sprent, R.F. Denison. 2010. Multiple evolutionary origins of legume traits leading to extreme rhizobial differentiation. New Phytol. 187:508-520.
Oono R., R. F. Denison, and E. T. Kiers. 2009. Tansley review: Controlling the reproductive fate of rhizobia: how universal are legume sanctions? New Phytologist 183:967-979.
Ratcliff W. C., P. Hawthorne, M. Travisano, and R. F. Denison. 2009. When stress predicts a shrinking gene pool, trading early reproduction for longevity can increase fitness, even with lower fecundity. PLoS One 4:e6055.
Sadras, V.O., R.F. Denison. 2009. Do plant parts compete for resources? An evolutionary viewpoint. New Phytologist 183:565-574.
Ratcliff, W.C., R.F. Denison. 2009. Rhizobitoxine producers gain more poly-3-hydroxybutyrate in symbiosis than do competing rhizobia, but reduce plant growth. ISME Journal 3:870-872.
Kiers E. T., R. F. Denison. 2008. Sanctions, cooperation, and the stability of plant-rhizosphere mutualisms. Annual Review of Ecology, Evolution, and Systematics 39:215-236.
Ratcliff, W. C., S. V. Kadam, and R. F. Denison. 2008. Polyhydroxybutyrate supports survival and reproduction in starving rhizobia. FEMS Microbiology Ecology 65:391-399.
Mitchell, A.E, Y.J. Hong, E. Koh, D.M. Barrett, D.C. Bryant, R.F. Denison, and S Kaffka. 2007. Ten-year comparison of the influence of organic and conventional crop management practices on the content of flavonoids in tomatoes. J. Agric. Food Chemistry 55:6154-6159
Kiers, E.T., M. Hutton, R.F. Denison. 2007. Human selection and the relaxation of legume defences against ineffective rhizobia. Proceedings of the Royal Society B 274: 3119-3126.
Denison, R.F., D.C. Bryant, and T.E. Kearney. 2004. Crop yields over the first nine years of LTRAS, a long-term comparison of field crop systems in a Mediterranean climate. Field Crops Research 86:267-277.
Martini E. A., J. S. Buyer, D. C. Bryant, T. K. Hartz, D. Barrett, and R. F. Denison. 2004. Yield increases during the organic transition: improving soil quality or increasing experience? Field Crops Research 86:255-266.
Okano, Y., K.R. Hristova, C. Leutenegger, L. Jackson, R.F. Denison, B. Gebreyesus, D. LeBauer, and K.M. Scow. 2004. Effects of ammonium on the population size of ammonia-oxidizing bacteria in soil -- Application of real-time PCR. Applied and Environmental Microbiology 70:1008-1016.
Kiers E. T., R. A. Rousseau, S. A. West, and R. F. Denison. 2003. Host sanctions and the legume-rhizobium mutualism. Nature 425:78-81.
Denison R. F., E. T. Kiers, and S. A. West. 2003. Darwinian agriculture: when can humans find solutions beyond the reach of natural selection? Quarterly Review of Biology 78:145-168.
Denison R. F., C. Bledsoe, M. L. Kahn, F. O'Gara, E. L. Simms, and L. S. Thomashow. 2003. Cooperation in the rhizosphere and the "free rider" problem. Ecology 84:838-845.
Kinraide T. B., R. F. Denison. 2003. Strong inference, the way of science. American Biology Teacher 65:419-424.
West, S.A., E.T. Kiers, E.L. Simms & R.F. Denison. 2002. Sanctions and mutualism stability: why do rhizobia fix nitrogen? Proceedings of the Royal Society 269:685-694.
Denison R. F. 2000. Legume sanctions and the evolution of symbiotic cooperation by rhizobia. American Naturalist 156:567-576.
Hasegawa, H., D.C. Bryant, and R.F. Denison. 2000. Testing CERES model predictions of crop growth and N dynamics, in cropping systems with leguminous green manures in a Mediterranean climate. Field Crops Research 67:239-255.
Jacobsen K. R., R. A. Rousseau, and R. F. Denison. 1998. Tracing the path of oxygen into birdsfoot trefoil and alfalfa nodules using iodine vapor. Botanica Acta 111:193-203.
McGuire, A.M., D.C. Bryant, and R.F. Denison. 1998. Wheat yields, nitrogen uptake, and soil moisture following winter legume cover crop vs. fallow. Agron. J. 90:404-410.
Denison R. F., R. Russotti. 1997. Field estimates of green leaf area index using laser-induced chlorophyll fluorescence. Field Crops Research 52:143-150.
Denison R. F., T. B. Kinraide. 1995. Oxygen-induced depolarizations in legume root nodules. Possible evidence for an osmoelectrical mechanism controlling nodule gas permeability. Plant Physiology 108:235-240.
Denison R. F., J. F. Witty, and F. R. Minchin. 1992. Reversible O2 inhibition of nitrogenase activity in attached soybean nodules. Plant Physiology 100:1863-1868.
Denison R. F., D. B. Layzell. 1991. Measurement of legume nodule respiration and O2 permeability by noninvasive spectrophotometry of leghemoglobin. Plant Physiology 96:137-143.
Denison R. F., B. Caldwell, B. Bormann, L. Eldred, C. Swanberg, and S. Anderson. 1976. The effects of acid rain on nitrogen fixation in western Washington coniferous forests. Water Air and Soil Pollution 8:21-34. My first publication, funded by my first grant, funded by the National Science Foundation's since-abandoned Student Originated Studies program, when I was an undergrad at The Evergreen State College.