First, the globe may neither warm -- nor dry regionally -- as predicted by currently-in-vogue climate models. Second, the increase in the atmosphere's CO2 concentration may confer upon plants, and possibly animals as well, an ability to better cope with higher temperatures, as explained in considerable detail in our major report The Specter of Species Extinction; and it may likewise compensate, or possibly even more than compensate, for regionally drier conditions, as indicated by the results of several studies we have reviewed and archived in our Subject Index under the heading of Water Status of Soil (Field Studies). Third, increases in all three of these factors -- temperature, degree of aridity and atmospheric CO2 concentration -- may induce rapid genetically-based evolutionary changes in both plant and animal species that may enable them to (1) successfully cope with any negative effects of increases in temperature and aridity, and (2) capitalize upon the positive biological effects of increases in the air's CO2 content. In what follows, therefore, we briefly review the findings of some of these genetically-oriented studies.

Concentrating on the first of the three environmental factors of major concern, i.e., temperature, Jump et al. (2006) introduce their study of potential tree responses to global warming by noting that "one of the basic assumptions in the study of plant adaptation to environment (genecology) is that natural selection in different environments generates genetic clines that correlate with environmental clines." Within this context, they further state that "temperature is of major importance as a selective agent causing population differentiation over altitudinal and latitudinal clines," citing Saxe et al. (2001), and they opine that "temporal changes in gene frequency that result from global warming should therefore mirror spatial changes observed with decreasing altitude and latitude," which changes are typically manifest in certain alleles that "may be confined to, or occur preferentially in, different sites with contrasting environmental conditions."

As a test of this hypothesis, the four researchers say they "combined population genomic and correlative approaches to identify adaptive genetic differentiation linked to temperature within a natural population of the tree species Fagus sylvatica L. [European beech] in the Montseny Mountains of Catalonia, northeastern Spain," concentrating on three areas: the upper treeline (high Fagus limit, HFL), the lower limit of F. sylvatica forest (low Fagus limit, LFL), and an area of the forest interior.

With respect to the temperature differential between the HFL and LFL locations, they report that the 648-m altitudinal difference that separates them "equates to a mean temperature difference of 3°C ... based on the altitudinal lapse rate of 0.51°C per 100 m reported by Penuelas and Boada (2003) for Montseny." Likewise, with respect to the change in temperature due to the region's manifestation of 20th-century global warming, they report that "by 2003, temperatures had increased by approximately 1.65°C when compared with the 1952-1975 mean," which temperature change, as they see it, "is likely to represent a strong selection pressure."

Numerous tests conducted by Jump et al. on the data they collected indicate that the frequency of a particular F. sylvatica allele showed a predictable response to both altitudinal and temporal variations in temperature, with a declining frequency and probability of presence at the HFL site that the Spanish research team determined to be "in parallel with rising temperatures in the region over the last half-century." As a result, they say their work "demonstrates that adaptive climatic differentiation occurs between individuals within populations, not just between populations throughout a species geographic range," which further suggests, in their words, that "some genotypes in a population may be 'pre-adapted' to warmer temperatures," as suggested by Davis and Shaw (2001). In addition, they went on to suggest that "the increase in frequency of these genotypes," which occurred in their study in parallel with rising temperatures, "shows that current climatic changes are now imposing directional selection pressure on the population," and that "the change in allele frequency that has occurred in response to this selection pressure also demonstrates that a significant evolutionary response can occur on the same timescale as current changes in climate," additionally citing in this regard the studies of Davis et al. (2005), Jump and Penuelas (2005) and Thomas (2005).

In concluding the report of their findings, Jump et al. suggest that an evolutionary response to global warming of the type they describe is likely already "underway," which further suggests -- to us, at least -- that many species of plants likely will not be forced to migrate either poleward in latitude or upward in altitude in response to global warming, in contradiction of what climate alarmists adamantly claim. Rather, as we have long contended, they will have the opportunity to so shift their ranges (i.e., expand them) at the cold-limited boundaries of their ranges, but they may not be forced to make any major changes at the heat-limited boundaries of their ranges, due in part to the phenomenon elucidated by Jump et al.

Focusing on the second of the three environmental factors of major concern, i.e., aridity, Franks et al. (2007) compared plant phenotypic and fitness values of ancestral, descendant, and ancestral x descendant hybrid genotypes grown simultaneously under conditions that mimicked a pre- and post-change environment, where the environmental change of which they took advantage was a switch from above- to below-average precipitation in southern California (USA) that led to abbreviated growing seasons from 2000 to 2004, while the plant they studied was Brassica rapa L., more commonly known as field mustard.

Fortuitously, as they describe it, they had "collected B. rapa seed in 1997, before the drought, and then again in 2004 from two populations," a dry site and a wet site. Hence, they could grow -- at the same time and under the same circumstances, in a new set of experiments -- plants that had experienced extended drought conditions (descendants) and plants that had not experienced such conditions (ancestors), as well as hybrids of the two; and they could see if flowering times (FT) differed as would be expected from life history theory, which "predicts that the optimal FT in annual plants will be shorter with shorter growing seasons," such as those that were imposed by the extended drought that occurred between the two times of their seed collecting. In following this protocol, the researchers did indeed find that "the abbreviated growing seasons caused by drought led to the evolution of earlier onset of flowering," such that "descendants bloomed earlier than ancestors, advancing first flowering by 1.9 days in one study population and 8.6 days in another." In addition, they report that "the intermediate flowering time of ancestor x descendant hybrids supports an additive genetic basis for divergence."

In light of their robust findings, Franks et al. write that "natural selection for drought escape thus appears to have caused adaptive evolution in just a few generations," further noting that "abundant evidence has accumulated over the past several decades showing that natural selection can cause evolutionary change in just a few generations (Kinnison and Hendry, 2001; Reznick and Ghalambor, 2001)." Indeed, they say their results "provide evidence for a rapid, adaptive evolutionary shift in flowering phenology after a climatic fluctuation," which "adds to the growing evidence that evolution is not always a slow, gradual process but can occur on contemporary time scales in natural populations," and, we would add (as was the case in this study and the preceding and following one), in response to real-world environmental changes.

Last of all, in a study that delves a little deeper into the subject and that deals with the third of the three environmental factors of major concern, i.e., atmospheric CO2 content, Rae et al. (2007) note that various studies "are beginning to identify genes that appear sensitive to elevated CO2 (Gupta et al., 2005; Taylor et al., 2005; Ainsworth et al., 2006)," noting further that "leaf growth responses to elevated CO2 have been found in Populus," and that "quantitative trait loci (QTL) for this response [have been] determined (Rae et al., 2006)."

Continuing in this vein, and working with a three-generation Populus pedigree generated by the hybridization of two contrasting Populus species -- where two full-siblings from the resulting F1 family were crossed to form an F2 family -- they grew cuttings of the different generations for 152 days in lime-free compost in plastic tubes buried to a depth of 10 cm out-of-doors in open-top chambers maintained at either ambient atmospheric CO2 concentrations or concentrations on the order of 600 ppm, while measuring various plant properties and physiological processes and determining QTL for above- and below-ground growth and genotype-by-environment interactions.

This work revealed, in the words of the four UK researchers, that "in the F2 generation, both above- and below-ground growth showed a significant increase in elevated CO2," and that "three areas of the genome on linkage groups I, IX and XII were identified as important in determining above-ground growth response to elevated CO2, while an additional three areas of the genome on linkage groups IV, XVI and XIX appeared important in determining root growth response to elevated CO2." These findings, as they describe them, "quantify and identify genetic variation in response to elevated CO2 and provide an insight into genomic response to the changing environment." As for their implications, they state that the combination of their mapping analysis with other high-throughput technologies now available in systems biology (Taylor et al., 2005) "should lead to an understanding of microevolutionary response to elevated CO2 ... and aid future plant breeding and selection."

In conclusion, it is becoming ever more clear that earth's plants possess amazing genetic potential to cope with major environmental changes over amazingly short time scales, and in the case of the ongoing rise in the air's CO2 content, to actually take advantage of that change and perform even better in the future than they did in the past, either with or without the help of man.

References
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Davis, M.B. and Shaw, R.G. 2001. Range shifts and adaptive responses to Quaternary climate change. Science 292: 673-679.

Davis, M.B., Shaw, R.G. and Etterson, J.R. 2005. Evolutionary responses to changing climate. Ecology 86: 1704-1714.

Franks, S.J., Sim, S. and Weis, A.E. 2007. Rapid evolution of flowering time by an annual plant in response to a climate fluctuation. Proceedings of the National Academy of Sciences USA 104: 1278-1282.

Gupta, P., Duplessis, S., White, H., Karnosky, D.F., Martin, F. and Podila, G.K. 2005. Gene expression patterns of trembling aspen trees following long-term exposure to interacting elevated CO2 and tropospheric O3. New Phytologist 167: 129-142.

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