Working with the field mustard (Brassica rapa) plant, Franks et al. (2007) compared "phenotypic and fitness values of ancestral, descendant, and ancestral x descendant hybrid genotypes grown simultaneously under conditions that mimicked those before and after a switch from above-average to below-average precipitation in southern California (USA), which led to abbreviated growing seasons from 2000 to 2004. 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.

This work revealed, in the researchers' words, that as predicted, "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." Moreover, they say that "the intermediate flowering time of ancestor x descendant hybrids supports an additive genetic basis for divergence." In consequence of these observations, therefore, they concluded that "natural selection for drought escape thus appears to have caused adaptive evolution in just a few generations," further stating 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)."

In discussing the significance of their findings, Franks et al. 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), in response to real-world climatic changes.

In a follow-up study conducted with the same plant material, Franks and Weis (2008) found that several life-history traits "differed between the ancestral genotypes collected before and descendant genotypes collected after the natural drought," stating that "this shows directly that an evolutionary change in the life-history traits has occurred during a 5-year drought." They also report that "the evolutionary changes in trait levels following the drought are consistent with predictions from life-history theory," since "the drought selected for individuals that flowered earlier, continued to flower for longer given sufficient resources, and produced a more consistent, evenly distributed pattern of flowering over time," which suite of changes, in their words, constitutes "a true genetically based evolutionary change rather than an expression of phenotypic plasticity."

Working in Spain's Garraf Natural Park with Fumana thymifolia (a small shrub that occurs around the Mediterranean Basin), Jump et al. (2008) sought to determine whether reduced seedling establishment observed as a consequence of climate manipulation is a random or selective process, in an attempt to answer what they call "the key question" -- Does climate change provoke evolutionary change within natural populations?

The seven scientists' study had an unaltered control treatment, a drought treatment that employed automatically-activated transparent plastic shields that covered a third of the plots in response to rainfall and retreated when rainfall stopped (which decreased soil moisture by about 20%), and a warming treatment that employed reflective covers that reduced nighttime re-radiation of energy received from the sun during the prior daylight hours from another third of the plots (which increased temperature by about 1°C).

As a result of these environmental interventions, Jump et al. report that over the 7-year period 1999-2005, mean yearly seedling density per treatment was significantly reduced in the drought and warming treatments compared with the control treatment, and that "when compared against control samples, high single-locus genetic divergence occurred in drought and warming treatment samples, with genetic differentiation up to 37 times higher than background (mean neutral locus) genetic differentiation."

In discussing their findings, the researchers say they suggest that the significant reduction in seedling survival they observed in the drought and warming treatments "results from an episode of selection for individuals tolerant of the modified climatic conditions and is not due simply to a random reduction in plant establishment," which implication, in their words, "reinforces results reported by other authors that show that genetic variability for climate-related traits exists within natural plant populations (Hamrick and Holden, 1979; Cobb et al., 1994; Kelly et al., 2003; Mitton and Duran, 2004; Franks et al., 2007)."

Jump et al. thus conclude that contemporary climate change "is driving changes in gene frequency within natural plant populations," and that these changes "are occurring on the same time scale as current climatic changes, based on preexisting genetic variability within populations," additionally citing, in this regard, the supportive findings of Jump and Penuelas (2005), Thomas (2005), Jump et al. (2006) and Reusch and Wood (2007). What is more, they say that this ability to rapidly adapt to rapid climate change may increase the persistence of species "beyond that predicted under a species-based climate envelope approach," such as is typically used by climate alarmists to justify their prediction of impending extinctions of huge numbers of species.

Therefore, in a conclusion that clearly repudiates the catastrophic extinction scenario, Jump et al. say their results actually demonstrate "that rapid evolution in response to climate change may be widespread in natural populations, based on genetic variation already present within the population," which likelihood is becoming ever more evident with each new study that investigates the subject. Hence, it is reasonable to expect that earth's plants are likely to be much more resilient to rising temperatures and reductions in precipitation than the people of the world have long been led to believe.

References
Cobb, N., Mitton, J.B. and Whitham, T.G. 1994. Genetic variation associated with chronic water and nutrient stress in pinyon pine. American Journal of Botany 81: 936-940.

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.

Franks, S.J. and Weis, A.E. 2008. A change in climate causes rapid evolution of multiple life-history traits and their interactions in an annual plant. Journal of Evolutionary Biology 21: 1321-1334.

Hamrick, J.L. and Holden, L.R. 1979. Influence of microhabitat heterogeneity on gene frequency distribution and gametic phase disequilibrium in Avena barbata. Evolution 33: 707-711.

Jump, A.S., Hunt, J.M., Martinez-Izquierdo, J.A. and Penuelas, J. 2006. Natural selection and climate change: temperature-linked spatial and temporal trends in gene frequency in Fagus sylvatica. Molecular Ecology 15: 3469-3480.

Jump, A.S. and Penuelas, J. 2005. Running to stand still: adaptation and the response of plants to rapid climate change. Ecology Letters 8: 1010-1020.

Jump, A.S., Penuelas, J., Rico, L., Ramallo, E., Estiarte, M., Martinez-Izquierdo, J.A. and Lloret, F. 2008. Simulated climate change provokes rapid genetic change in the Mediterranean shrub Fumana thymifolia. Global Change Biology 14: 637-643.

Kelly, C.K., Chase, M.W., de Bruijn, A., Fay, M.F. and Woodward, F.I. 2003. Temperature-based population segregation in birch. Ecology Letters 6: 87-89.

Kinnison, M.T. and Hendry, A.P. 2001. The pace of modern life II: from rates of contemporary microevolution to pattern and process. Genetica 112: 145-164.

Mitton, J.B. and Duran, K.L. 2004. Genetic variation in pinon pine, Pinus edulis, associated with summer precipitation. Molecular Ecology 13: 1259-1264.

Reusch, T.B.H. and Wood, T.E. 2007. Molecular ecology of global change. Molecular Ecology 16: 3973-3992.

Reznick, D.N. and Ghalambor, C.K. 2001. The population ecology of contemporary adaptations: what empirical studies reveal about the conditions that promote adaptive evolution. Genetica 112: 183-198.

Thomas, C.D. 2005. Recent evolutionary effects of climate change. In: Lovejoy, T.E. and Hannah, L. Eds., Climate Change and Biodiversity, Yale University Press, Cambridge, Massachusetts, USA, pp. 75-88.