Climate change and agriculture

Climate change and agriculture

TREE vol. 6, no. 3, March 1991 ized above suggest that there are two distinct community-construction processes, one based on invasions, the other on...

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TREE vol. 6, no. 3, March


ized above suggest that there are two distinct community-construction processes, one based on invasions, the other on speciations. The issue to be resolved in the future is the delineation of circumstances under which one of the two processes dominates the development of communities in nature. H. Re$t Akqakaya AppliedBiomathematics, 100North CountryRoad, Setauket, NY11733, USA Lev R. Ginzburg Deptof EcologyandEvolution,StateUniversityof NewYork at Stony Brook,StonyBrook,NY11794, USA

References 1 Nee, S. (1990) Trends Ecol. Evol. 5, 337-340 2 Gardner, M.R. and Ashby, W.R. (1970) Nature 228,784 3 May, R.M. (1972) Nature 238,413-414 4 Roberts, A. (1974) Nature 251, 607-608 5 Tregonning, K. and Roberts, A. (1979) Nature 281, 563-564 6 Roberts, A. and Tregonning, K. (1980) Nature 288,265-266 7 Robinson, J.V. and Valentine, W.D. (1979) J. Theor. Biol. 81,91-104 6 Post, W.M. and Pimm, S.L. (1983) Math. Biosci. 64, 169-l 92 9 Taylor, P.J. (1988) J. Theor. B/o/. 135, 569-588 10 Gillespie, J.H. 11977) Evolution 31, 85-90 11 Lewontin, R.C., Ginzburg, L.R. and

Tuljapurkar, S.D. (1978) Genetics 88, 149-170 12 Aoki, K. (1980) J. Math. Bioi. 9, 133-146 13 Spencer, H.G. and Marks, R.W. (1988) Genetics 120,605-613 14 Ginzburg. L.R., Akqakaya, H.R. and Kim, J. (1988) J. Theor. B/o/. 133, 513-523 15 AkCakaya, H.R. and Ginzburg, L.R. (1989) in Evolutionary Biology of Transient Unstable Populations (Fontdevila, A., ed.), pp. 32-42, SpringerVerlag 16 Levins, R. (1968) Evolution in Changing Environments, Princeton University Press 17 Pianka, E.R. (1973) Annu. Rev. Ecol. syst. 4, 53-74 18 Colwell, R.K. and Futuyma, D.J. (1971) Ecology 52, 567-576

Climate Change and Agriculture In their recent article in TREE’, Parry et al. refer to an earlier paper2 showing the present theoretical limits in the UK for the successful ripening of grain maize. We have much evidence that the practical limits are considerably further north. In 1978, we obtained3 highly successful ripening of a number of inbred lines, F,, F, and backcross families of grain maize in North Humberside, UK, corresponding almost exactly with the eastern edge of the 1.5”C hypothetical line in Fig. 2 of the TREE article by Parry et al. The best performance was of one F, family that averaged 140 days from seed to harvest. Admittedly these plants were given a good start, because the seeds were sown in the glasshouse and the seedlings planted out 25 days later. With families obtained by crossing selected lines from the USA with some lines developed by R.A. Gunn, we have now improved on this with

direct sowing into the field (O.T. Hassan, PhD thesis, Hull University, 1990). One F, family sown in midMay 1988 required an average of 148 days to reach maturity, while in 1989 the same family, sown at the end of April, required only 126-130 days, and this with seeds drying to 33% moisture content, on average. Whereas in 1989 there was a long period with warm sunny days and no rain, the conditions in 1978 and 1988 were nowhere near ideal, but early maturity and good yields were achieved. Furthermore, the plants were remarkably clean, even though maize is grown in Humberside for fodder and grain maize has been grown in our experimental field for over 14 years. Our experiments were primarily to select for good germination at low temperatures (6°C) and to study the genetics of the variation for this character. The early maturity described above was the result of natu-

ral variation present in the inbred lines that had been selected for their ability to germinate at 6”C, and thus shows the enormous potential of this material for use in short seasons that begin cold and end cool (or, indeed, hot as would be the situation with the ‘spring’ crop in Pakistan or Iraq). David A. Jones Deptof Botany,Universityof Florida,Gainesville, FL32611-2009, USA

Obaid T. Hassan Deptof Applied Biology, Universityof Hull, Hull HU67RX,UK

References 1 Parry, M.L., Porter, J.H. and Carter, T.R. (1990) Trends Ecol. Evol. 5,318-322 2 Parry, M.L., Carter, T.R. and Porter, J.H. (I 989) J. R. Agric. Sot. Engl. 150, 120-131 3 Maryan, B. and Jones, D.A. (1985) Euphytica 34,475-481