Evolutionary Responses to Advanced article Climate Change Article Contents . Introduction David K Skelly, Yale University, New Haven, Connecticut, USA . Observed Genetic Changes . Adaptations to Climate Change L Kealoha Freidenburg, Yale University, New Haven, Connecticut, USA . Changes in Selection Pressures . Rate of Evolution versus Rate of Climate Change . Extinction Risks . Future Prospects Online posting date: 15th September 2010 Biological responses to contemporary climate change are Everything from heat tolerance, body shape and size, and abundantly documented. We know that many species are water use physiology of plants is strongly related to the cli- shifting their geographic range and altering traits, mate conditions within a species range. From these obser- including the timing of critical life history events such as vations, a natural assumption would be that a great deal of research on the role of contemporary climate change in birth, flowering and diapause. We also know from com- driving evolutionary responses has taken place. Although parative studies of species found across the earth that a there has been an increasing amount of research very strong relationship exists between a species trait and the recently, in fact there is relatively little known about the links climatic conditions in which it is found. Together, these between contemporary climate change and evolution. The observations suggest that ongoing climate change may reasons for this are not hard to determine. There is abundant lead to evolutionary responses. Where examined, evo- documentation of biological responses to climate change lutionary responses have been uncovered in most cases. (Parmesan, 2006). Species distributions are moving pole- The effort needed to disentangle these genetic contri- ward, the timing of life history events are shifting to reflect butions to responses is substantial and so examples are lengthened growing seasons and traits such as body size are few. In general, the documented evolutionary responses changing. The problem, explored in more detail later, is that feature traits that are likely to alter responses to seasonal these changes may or may not have an evolutionary com- ponent. The implicit assumption has been that there is none change or to change tolerance to environmental con- (e.g. Thomas et al., 2004) and that any observed phenotypic ditions. Currently available research provides hints that changes are the product of phenotypic plasticity. See also: climate-mediated evolutionary responses are likely to be Biotic Response to Climatic Change enormously diverse. It is clear, that the current presump- In part, this is because plasticity is known to be wide- tion of many climate change scientists, that evolution can spread and can be readily documented using experiments in be safely ignored, does not have a basis in evidence. which organisms are raised under various conditions. It is much more challenging to parse the relative contributions of plastic and evolved responses. By adding organisms from multiple population origins to experiments aimed at documenting responses to a changing environment, we can first determine whether populations have diverged in their Introduction responses. Verifying whether such divergence has a genetic basis then requires an additional step. The most straight- Climate is well known as a mediator of evolutionary forward possibility involves directly documenting relevant change. Related species that inhabit different climate genetic change. However, in many cases, that will not be regimes differ in characteristic ways that are repeated possible and we will be left with a situation in which across taxonomic groups (e.g. Huey and Kingsolver, 1993). divergence among populations could be explained by a genetic effect, by an inherited nongenetic effect or by some combination. One of many possible examples of a non- ELS subject area: Ecology genetic effect is the influence mothers can have on their offspring by better provisioning their eggs. Such maternal How to cite: or paternal effects can be bred out of offspring by rearing Skelly, David K; and Freidenburg, L Kealoha (September 2010) them under common conditions for multiple generations. Evolutionary Responses to Climate Change. In: Encyclopedia of Life Following such treatment, we can attribute observed Sciences (ELS). John Wiley & Sons, Ltd: Chichester. divergence to a genetic origin. Alternatively, we can esti- DOI: 10.1002/9780470015902.a0022545 mate the size of genetic effects relative to estimated ENCYCLOPEDIA OF LIFE SCIENCES & 2010, John Wiley & Sons, Ltd. www.els.net 1 Evolutionary Responses to Climate Change inherited nongenetic effects through half-sib mating this species, it is not clear what type of selection pressure designs (Gienapp et al., 2008). Given these challenges, it is (e.g. thermal or seasonal selection) is causing it. perhaps not surprising that, in the great majority of cases for which we know changes are taking place, the potential Alcohol dehydrogenase for an evolutionary basis to changing climate is unexplored. The fruit fly, Drosophila melanogaster, is polymorphic for Here, we focus on what we do know about micro- an enzyme, alcohol dehydrogenase (Adh), that metabolises evolution in response to contemporary climate change. alcohol. Adh exhibits a strong latitudinal cline. In labora- Given the recent nature of the efforts, the evidence is tory experiments, temperature is one of the factors that impressive. Even when confronted by large-scale, multi- influences Adh allele frequencies. In one study (Umina faceted and rapid change in climate, there is evidence from et al., 2005), researchers resampled sites in coastal Aus- various organisms that evolution takes place. In many tralia for which historical data were available (collected in cases, these changes are detectable in just a few generations. 1979 and 1982). Across the sampled latitudinal cline, the A larger problem is that we know little about the con- allele associated with warmer climates had increased in sequences of these responses. Do they help to protect spe- frequency. Here again, as in the previous example, we have cies from further impacts of climate change? In what senses a species with a known genetic latitudinal cline shifting does evolutionary response represent a type of impact? frequencies in response to a changing environment. And when we look to the future, can we expect the sig- nificance of evolutionary responses to magnify? Later, we Mosquito diapause document what is known about evolutionary responses to At the end of the growing season based on a daylength cue, contemporary climate change and lay out some challenges the pitcher plant mosquito (Wyeomyia smithii) produces and opportunities for future researchers. diapausing larvae (Bradshaw and Holzapfel, 2001). The mosquito is polymorphic for the daylength cue. Com- parison of contemporary samples with historic ones Observed Genetic Changes revealed that the shorter critical daylength morph has increased. Observations of genetic change associated with changing climate provide critical evidence for evolutionary responses. Salamander colour polymorphism Genetic evidence is also difficult to collect and can be chal- The salamander Plethodon cinereus has a genetically based lenging to interpret. It is no accident that much of the evi- colour polymorphism (Highton, 1975). Red-backed forms dence we discuss in this section comes from fruit flies. These tend to be more common in cooler microclimates, whereas model organisms have been well characterised genetically, a grey, or lead-backed form increases in frequency in and the relationship between genotype, phenotype and warmer microclimates. Gibbs and Karraker (2005) exam- performance is as well understood as it is for any organism ined over 50 000 individuals collected between 1908 and on earth. This immense background knowledge has given fly 2004 from a range of latitudes and altitudes at 558 sites. biologists the motivation and perspective from which to Their results showed that the frequency of the lead-backed sample field populations. For the most part, long-term form increased over the course of a century during which genetic monitoring was not initiated with climate change in temperature increased by approximately 0.78C. mind. Nevertheless, these data sets are now invaluable for the insights they offer to those understanding how, and how fast, species respond genetically to climate change. Adaptations to Climate Change Chromosomal inversions Reviews of biological responses to contemporary climate Balanya et al. (2006) analysed global patterns of chromo- change have emphasised two patterns: species are moving somal inversion frequencies in Drosophila subobscura. and, within a given location, timing of life history events is Data were collected for a half-century in the species native shifting (Parmesan, 2006). In one review, nearly 60% of range, stretching from northern Europe to north Africa. more than 1500 species examined had undergone measur- Additional data in their introduced range (North and able changes in either phenology or distribution during the South America) go back to shortly after their introduction course of long-term observations (Parmesan and Yohe, in 1979. It has long been known that inversion genotypes 2003; Root et al., 2003). In the majority of cases, responses sorted with latitude. Compared with historical samples, were in directions expected under changing climate. researchers found that warm-associated inversions in Among species