Physiological Ecology

2744 Evolutionary Ecology | Physiological Ecology See also: Transport over Membranes.

Further Reading Elder JW (1959) The dispersion of marked fluid in turbulent shear flow. Journal of Fluid Mechanics 5: 544–560.

Fischer HB (1967) The mechanics of dispersion in natural streams. Journal of the Hydraulics Division, ASCE 93(6): 187–215. Fischer HB, List EJ, Koh RC, Imberger J, and Brooks NH (1979) Mixing in Inland and Coastal Waters. New York: Academic Press. Rutherford JC (1994) River Mixing. Chichester: Wiley. Taylor GI (1954) The dispersion of matter in turbulent flow through a pipe. Proceedings of the Royal Society of London, Series A 223: 446–468.

Physiological Ecology B K McNab, University of Florida, Gainesville, FL, USA Published by Elsevier B.V.

Thermal Biology Energetics Geographical Patterns Limits to Geographical Distributions Gas Exchange

Photosynthesis Nutrients and Diets The Future Further Reading

Physiological ecology is a hybrid field that uses of the tools of physiology to examine aspects of the ecology and evolution of organisms. Although elements of this approach can be traced back to the mid-nineteenth century, concerted efforts started especially after 1950 by such people as Per Scholander, Laurence Irving, W. D. Billings, H. A. Mooney, N. I. Kalabuchov, and Knut and Bodil Schmidt-Nielsen. Its principal preoccupation is to examine how organisms adjust (i.e., adapt) their characteristics to facilitate their survival and reproduction. Such work has implications for the thermal and osmotic limits to geographic distribution, the ability to tolerate xeric or mesic environments, the adjustments required to tolerate low barometric pressures at high altitudes and high pressures in deep-sea environments, the means by which consumers can handle plant secondary compounds in food, and how photosynthesis is modified to meet environmental conditions. Unlike some other areas of ecology, physiological ecology, a comparatively new branch of ecology, does not have a well-developed, unified theoretical basis, except that the responses of organisms are expected to conform to the principles of physics and chemistry. Some species, however, are able to avoid these limits through behavioral evasions. Thus, burrowing habits reduce the necessity to respond directly to extreme climates, as is required of species exposed to the macroenvironment. Equally, the use of daily torpor or hibernation permits some species to avoid the harshest conditions in cold-temperate or desert environments. In a similar manner, some desert plants evade water shortages with deep tap roots that penetrate groundwater or by becoming dormant during dry periods.

The best way to illustrate the contribution of physiological ecology to the understanding of ecological relationships is to give several diverse examples of its analytical power.

Thermal Biology The physiological distinction in animals that has the greatest ecological impact is the difference between ectotherms and endotherms. Most species are ectotherms, which have body temperatures that usually conform to the most prevalent environmental temperatures, whereas endotherms, most notably birds and mammals, have body temperatures that, within limits, are independent of ambient temperature (Figure 1). As a consequence, endotherms can be active at low ambient temperatures, but only by paying the cost via metabolism of maintaining this temperature differential (Figure 1). Ectotherms, on the other hand, are much more temperature dependent in their behavior, except as they are able to acclimate to temperature variations in the environment. Ectotherms and endotherms differ in a large number of ways, especially in their standard rates of metabolism. These rates, which in endotherms are called the basal rate of metabolism, are approximately 10 times the standard rate of ectotherms, when measured in ectotherms at a body temperature of 30  C (Figure 2). Only part of the difference between endotherms and ectotherms reflects the difference in body temperature, which in endotherms usually is between 36 and 42  C. Another difference is that endotherms have a flexible insulation that permits a

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Evolutionary Ecology | Physiological Ecology

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Figure 1 Body temperature and rate of metabolism in ectotherms and endotherms as a function of ambient temperature. Two insulations are indicated for the endotherm, where insulation 1 < insulation 2.

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endothermy, even with a decrease in rate of metabolism (Figure 4). Birds too underwent a reduction in size, if they really were derived from dinosaurs, although the intermediate steps in the evolution of birds are unknown, which prevents us from understanding how birds evolved endothermy. Endothermy independently evolved in many other clades, including some otherwise ectothermic lineages, namely sharks, billfishes, tuna, and sea turtles, which gives them a degree of independence from water temperature. These aquatic vertebrates maintain in their lateral muscles (sharks, tuna) and core (sea turtles) a limited temperature differential with water, or the heat produced in the muscles is shunted to warm the brain (billfish). Endothermy also repeatedly evolved in various insect groups in which the thoracic temperature is regulated through the contraction of flight muscles: heat loss, in the case of moths and bumblebees, is reduced by the presence of a hair coat. The thermal biology of these insects contrasts with that found in most butterflies, which like some lizards are basking ectotherms. The small size of all thermoregulating insects, however, prevents them from maintaining a continuous temperature differential with the environment. The closest that insects come to that capacity is found in some bees and wasps that may maintain a thermally constant nest through the collective activity of a colony. Even some plants maintain a temperature differential with the environment in reproductive structures through the regulation of the rate of metabolism in the enclosed tissues. This may occur in cool environments, as was found in skunk cabbages (Symplocarpus foetidus), which facilitates the release of attractants for pollinating insects, but it also has been found in tropical species, including the Amazon giant water lily (Victoria amazonica), an arum lily (Philodendron selloum), and some palms.

Figure 2 Log10 standard rate of metabolism in birds; eutherian, marsupial, and monotreme mammals; and lizards as a function of log10 body mass.

Energetics

reduction in the cost of maintaining a temperature differential with the environment (Figure 1). The rate of metabolism in ectotherms falls with a decrease in ambient temperature because body temperature decreases (Figure 1). As a result, ectothermy is a much cheaper form of existence. Endothermy has repeatedly evolved from ectothermy. How mammals evolved their endothermy from ancestral therapsids, which were presumably ectothermic, is unclear, but the large mass of therapsids may have given them some thermal constancy. The evolution of the earliest mammals was associated with a decrease in body size by a factor of up to 1000:1 (Figure 3). That decrease could have permitted the shift from ectothermy to

The quantitative physiological relationship most widely used in ecology is between rate of energy expenditure in animals and body mass (Figure 2). It is usually described as a power function: M ¼ a ? mb, where M is the rate of metabolism, for example, in kJ h1, a is a coefficient, m is body mass, usually in grams or kilograms, and b is a dimensionless power. The fitted power b varies, but is almost always <1.00 and usually between 0.67 and 0.75. There have been various attempts to derive the power of this relationship from what is called first principles, but their success has been debated and often contradictory. What is not in question, however, is that as a result of the power being positive, rate of metabolism increases with mass and because b is less than 1.00, the rate of metabolism per unit mass decreases with mass. This has led to some

2746 Evolutionary Ecology | Physiological Ecology 500 Pelycosauria Therapsida

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Figure 3 Skull length as a function of time in the Paleozoic, Mesozoic, and Cenozoic Periods in the phylogeny of mammals, including pelycosaurs, therapsids, and mammals. Modified from McNab BK (1971) On the ecological significance of Bergmann’s rule. Ecology 52: 845–854.

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Figure 4 Log10 standard rate of metabolism in reptiles and mammals as a function of log10 body mass with two suggested pathways by which rate of metabolism was modified in the evolution of the earliest mammals. Also indicated is the approximate time at which a complete secondary palate evolved, which suggests a partial shift from a lower (reptilian) rate of metabolism to a higher (mammalian) rate of metabolism. Modified from McNab BK (1971) On the ecological significance of Bergmann’s rule. Ecology 52: 845–854.

confusion: do large species have higher or lower rates of metabolism than small species? Both statements are true, but total rates of metabolism are the relevant rates. Although body mass is by far the most important factor influencing the standard rate of metabolism in both

endotherms and ectotherms, it does not account for all of its variation. An extensive argument has been brewing as to the factors that are responsible for the residual variation in standard rates in birds and mammals. For example, at any particular mass the ratio of the highest to the lowest basal rates in mammals equals at least 3 or 4:1 and is as high as 10:1. The disagreement on residual variation centers on whether most of it is associated with history, that is, phylogeny, or whether it is connected with the behavioral or ecological characteristics of species. The influence of phylogeny is difficult to separate from the other proposed factors on basal rate. Furthermore, all character states may not equally reflect historical factors. That rate of metabolism is determined by history without reference to resource availability in the environment is difficult to imagine. Basal rate in both birds and mammals correlates with food habits, climate, habitat, use of torpor, and an altitudinal or island distribution. Because these factors often correlate with taxonomy, basal rate also correlates with taxonomy. In ectotherms the residual variation in standard rate of metabolism is less than that found in endotherms, probably because endotherms have such high resource requirements that they often have to adjust their expenditures. Nevertheless, residual variation in lizards correlates with their food habits and climate. Activities other than body maintenance and thermoregulation influence energy expenditure. The cost of

Evolutionary Ecology | Physiological Ecology

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Figure 5 Log10 field rates of metabolism in birds, mammals, and lizards as a function of log10 body mass. Modified from Nagy KA, Girard IA, and Brown TK (1999) Energetics of free-ranging mammals, reptiles, and birds. Annual Reviews of Nutrition 19: 247–277.

terrestrial, aquatic, and aerial locomotion in animals has been documented. It increases with velocity and is much greater in runners and walkers than in fliers, which is greater than in swimmers. Swimmers have relatively low cost of transport because they are usually neutrally buoyant and use a much greater fraction of their surface area to exert a force against the environment. The cost of flight, however, depends on the degree to which a flier uses powered or gliding flight. The cost of activity in animals contributes to the cost of existence, as measured in field energy expenditures. Field energy expenditures, like standard rates of metabolism, increase as a power function of body mass (Figure 5). Field expenditures in vertebrates, often measured with doubly labeled water, are usually between two and four times the standard rate with a high variability depending on the immediate environmental conditions and behavior of the individuals examined. Birds and mammals that have high standard rates of metabolism for their body size also tend to have high field expenditures. High expenditures in standard and field rates are correlated with high rates of reproduction in endotherms; that is, the r–K dichotomy is ultimately based on a dichotomy in energy expenditure. Ectotherms, as would be expected from their low standard rates, have low field energy expenditures (Figure 5).

Geographical Patterns Zoologists have described a series of ecogeographic ‘rules’. The best known is Bergmann’s rule, which states that endotherms tend to be larger in colder climates. It has

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been advocated and denied repeatedly. Like other ‘rules’, it faces the twofold requirement of its validity and significance. Several different surveys have generally agreed that at least some mammals and birds conform to this rule. But conformation is complex: some species that conform may do so only over a limited latitudinal range. For example, the puma or mountain lion, Puma concolor, a large New World felid, conforms to this rule twice, in North America at latitudes >35  N and in South America at latitudes >20  S (Figure 6). Unfortunately, few groups have been sufficiently surveyed to know the extent to which they conform to this rule. Yet, even if a minority of species follows Bergmann’s rule, the increase in mass deserves an explanation. Explanations for Bergmann’s rule have been varied. The original explanation given by C. Bergmann was that large mammals have a low rate of metabolism and low cost of body maintenance. But, as seen above, that explanation uses mass-specific rates, which is a doubtful basis: large individuals and species have higher total rates of metabolism than small individuals and species. Furthermore, some ectotherms are larger at higher latitudes, which cannot be explained by a reduction in the cost of thermoregulation. In some cases a latitudinal increase in body mass in a smaller carnivore occurs beyond the latitudinal limits to the distribution of a larger, lower-latitude competitor (Figure 6), implying that the size difference is due to character displacement and that the increase in mass at higher latitudes of the smaller competitor is due to the absence of the larger species. Thus, the puma is smaller in the presence of the larger jaguar (Panthera onca), which is limited to tropical and warm-temperate regions. Body size in the puma correlates with prey size: pumas feed on smaller prey in the presence of jaguars and on larger prey in their absence (Figure 7). In other cases, the correlation of body size with latitude in some predators (e.g., Canis lupus) reflects changes in the size of the prey. In general, then, Bergmann’s rule may reflect food quality, quantity, and availability, and will occur only if it is energetically affordable. In contrast to Bergmann’s rule, Dehnel’s phenomenon describes a decrease in winter of the skeleton and nervous system in small mammals that are committed to continuous endothermy. This pattern was originally described in soricine shrews and has been subsequently seen in arvicoline rodents. The decrease in mass leads to a decrease in rate of metabolism, which presumably is its rationale. In this sense, Dehnel’s phenomenon is parallel to Bergmann’s rule in reflecting resource availability in the environment, an increase in body size if resources are available, or a decrease in body size if they are not. Another way of reducing energy expenditure in small mammals is to enter torpor. A significant difference, however, exists between small endotherms that conform to

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Figure 6 Head and body length in pumas (Puma concolor) and jaguars (Panthera onca) as a function of latitude. Modified from McNab BK (1971) On the ecological significance of Bergmann’s rule. Ecology 52: 845–854.

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Dehnel’s phenomenon and those that enter torpor: the first group is characterized by very high basal rates, whereas the latter is characterized by lower basal rates, a difference that can be seen between soricine and crocidurine shrews. Another ecogeographic rule is the ‘island rule’, which states that large continental mammals are smaller if established on islands, whereas small continental species are larger on islands. The various explanations that have been given for this pattern have a common element: resource availability, which may account for the radical decrease in the size of mammoths (Mammuthus primigenius) on

Wrangel island (Siberia); elephants and hippopotamuses on Mediterranean islands; and hippopotamuses on Madagascar. Small species, especially in the absence of species with which they share resources, become larger because of the relative abundance of resources. However, island endemics can become very large. This has occurred on elephant birds (Aepyornithidae) in Madagascar and moas (Emeidae) and herbivorous rails in New Zealand, which was permitted by the absence of any endemic terrestrial, herbivorous mammals on these large islands. Large brown bears (Ursus arctos) occur on Kodiak Island (Alaska) in the presence of huge salmon (Oncorhynchus spp.) populations. The ‘island rule’, depending as it does on resource availability, is parallel to the combination of Bergmann’s rule and Dehnel’s phenomenon. An ecogeographical pattern, which has not been dignified as a rule, is the increase in species diversity with a decrease in latitude. This pattern has been given a wide variety of explanations, but here the question is whether it has a physiological component. One is that tropical mammals and nonpasserine and passerine birds have lower rates of metabolism than temperate and polar species. Why that is the case may be complicated, but the reproductive output of birds and eutherian mammals correlates with rate of metabolism: a high rate of metabolism at high latitudes may be the means by which reproduction can be increased to compensate for high mortalities associated with harsh climatic conditions and, in the case of birds, high mortalities related to migratory habits. In contrast, resident tropical species tend to have longer life spans and lower rates of reproduction.

Evolutionary Ecology | Physiological Ecology

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Limits to Geographical Distributions Rinca

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As might be expected from the correlation of species diversity and energy expenditure with latitude, energy expenditure may be an important factor involved with the thermal limits to geographic distribution. For example, the limits to the winter distribution of birds in North America is closely associated with thermal isotherms, which implies that it correlates with long-term maximal rates of energy expenditure. Equally, some bats are limited to tropical and warm-temperate environments apparently in response to thermal conditions in the environment and not simply related to food habits, as might be the case in frugivores. The common vampire bat (Desmodus rotundus), which would not face a food shortage in temperate environments, is limited to regions in which the mean minimal temperature during the coldest month is 10  C. At 10  C D. rotundus has a rate of metabolism that is 65% greater than at 25  C as a result of poor body insulation. A further long-term increase in metabolism is possibly prohibited by the need to transport the ingested food, its high water content (which is often excreted during feeding), and the loss of much of the energy in ingested protein as urea. Another aspect of energetics in relation to distribution is found in island endemics: they tend to have low rates of metabolism, produced either through a decrease in body mass, or by a decrease in metabolism independent of body mass. These decreases may reflect reduced resource availability or life in environments with low species diversity, where predation and competition are greatly reduced and a high reproductive output unnecessary. This response occurs in the two groups of endotherms that are found on oceanic islands, birds and bats. Ectothermic vertebrates, including lizards, tortoises, and crocodiles, as might be expected from their low energy expenditures, are prominent on oceanic islands, often with a large mass. But even large ectotherms reduce energy requirements with a smaller mass on small islands (Figure 8). The geographical limits to distribution in ectotherms may also reflect physiological limitations. Although rate of metabolism may acclimate to various temperatures, this response is limited, and such limitations may set the thermal and geographical limits to distribution. Ectotherms that show behavioral temperature regulation, like many insects and lizards, are able to move into cool environments by differentially absorbing solar radiation, but they still face thermal limits dictated by ambient temperature. Thus, lizards of the genus Liolaemus are able to move to altitudes as high as 4300 m in the Andes by continuously basking in the sun, which is required to maintain a viable body temperature because ambient temperatures are as low as 5  C. At low altitudes basking time is reduced to prevent overheating.

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The necessity of maintaining a water balance may also limit the geographical distribution of species. The well-known capacity of some rodents to eat dry, proteinrich seeds and live in some of the most extreme deserts derives in part from behavioral adjustments, including being nocturnal and spending the day in closed burrows, but also requires the ability to conserve water by producing a highly concentrated urine. Some small mammals tolerate deserts by consuming foods with high water contents, especially insects, and therefore do not require the capacity to produce highly concentrated urines. Obviously, species with high rates of integumental evaporative water loss, such as amphibians, face serious problems in xeric environments, where they either are active only during wet periods and sequester during dry periods, often hibernating in cocoons constructed of multiple layers of shedded skin and dried mud, or they are prevented from living in such environments. Some arboreal anurans respond to seasonally dry conditions by spreading a lipid layer on their skin, becoming stationary, switching from integumental to pulmonary gas exchange, and switching nitrogenous waste products from urea to uric acid, all of which reduce water loss. Distribution in aquatic environments may be limited by both temperature and the osmotic concentration of water. These two factors, however, are not independent of each other because the ability to tolerate an external

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concentration different from that in a species’ blood and tissues requires an expenditure of energy, which is temperature dependent. As a result of these limitations, some aquatic species are limited to high external concentrations, as in marine environments, whereas others are restricted to freshwater.

Gas Exchange Most terrestrial animals live in environments in which the abundance of gases is relatively constant with oxygen at 21% and CO2 is <0.04%. Yet, many environments are characterized by different gas compositions, including high CO2 and low O2 concentrations in some aquatic environments and low barometric pressures at high altitudes (with gas composition remaining equal to that at sea level). At high altitudes, animals respond by increasing the affinity of hemoglobin and the hematocrit to facilitate the acquisition and transport of oxygen, whereas in stagnant aquatic environments similar changes will occur along with an increased capacity to buffer high levels of environmental CO2. Furthermore, the evolution of a terrestrial from an aquatic habit was associated with a shift from an oxygenpoor environment, due to the limited solubility of oxygen in water, to an oxygen-rich environment. This shift is usually associated with reduced levels of gas exchange, which further enhances life in a terrestrial environment through the reduction in evaporative water loss.

Photosynthesis All plants use C3 photosynthesis, which has been supplemented in some species with Crassulacean acid metabolism (CAM) and C4 photosynthesis. These two pathways are adaptations to dry environments. CAM photosynthesis, which occurs in about 10% of plant species, fixes CO2 in the dark and the resulting organic acids are deacidified during the day. Plants with CAM close their stomata during the day, which is an effective response to drought conditions and is preferentially found in desert-dwelling succulents, for example, cactuses and agaves, or in arboreal plants, for example, bromeliads and orchids, that is, in dry microenvironments. CAM has low levels of primary production. C4 photosynthesis occurs in only c. 5% of plant species, principally in monocotyledon sedges and grasses and in some xeric-tolerant dicotyledon families, including chenopods and euphorbs. This form of photosynthesis occurs most commonly in arid environments, especially in regions with warm-season rainfall. In environments with both C3 and C4 plants, C4 plants occur principally in microenvironments that are warm and dry. C3 plants, which constitute about 85% of all plant species, including

bryophytes, ferns, gymnosperms, and most dicotyledons and aquatic plants, preferentially occur in cooler and moister microenvironments. C3 photosynthesis is often limited by the amount of CO2 that is available, whereas C4 is usually saturated at relatively low CO2 concentrations. Thus, while C4 species has greater productive yields than C3 species at low CO2 concentrations, C3 species outcompetes C4 species at elevated CO2 concentrations. In Mexico, for example, there was an increase in C3 species about 9000 years ago, which correlated with an increase in CO2, in spite of a simultaneous increase in aridity, which based on water conservation presumably would have led to an increase in C4 species. C3 plants also have increased in abundance since the beginning of the industrial age, possibly in association with the increase in CO2.

Nutrients and Diets Plants have adapted to the differential occurrence of nutrients in the soil. For example, halophytes and metallophytes can survive in the presence of low concentrations of NaCl and high concentrations of heavy metals, respectively, and calcifuges are restricted to acidic soils and calcicoles are restricted to alkaline soils. These specialists survive in a much narrower range of ecological conditions, whereas most plants live within a less extreme range of conditions in the soil. Plants found in nutrient-rich soils produce more biomass than those living in nutrient-poor soils. The low primary production of plants with narrow soil tolerances conserve the acquired nutrients for long periods of time. A related aspect of nutrient acquisition is that herbivorous mammals intake large amounts of organic compounds, some of which are either difficult to digest, hinder digestion (e.g., tannins), or are toxic. Toxic compounds protect plants by reducing the consumption of consumers, and in extreme cases these plants may be completely avoided. This system is not only toxic to the animals that consume these substances, but also requires energy expenditures by the plants to synthesize them, often at the expense of growth and reproduction. Small herbivores, because of their low energy requirements, can avoid toxic plants by selecting high-quality food, but large species, because of their high requirements, usually cannot avoid toxic or indigestible plants and must use gut fermentation to aid in their digestion and detoxification.

The Future Physiological ecology, because it deals with the reaction of plants and animals to the physical–chemical conditions in the environment, can potentially make an important contribution to understanding the likely consequences of

Ecological Engineering | Phytoremediation

the predicted increase in global temperatures and dramatic shift in rainfall patterns resulting from an increase in atmospheric CO2 concentration. C3 photosynthetic plants under these conditions are likely to become even more abundant, as long as sufficient amounts of water are available, but if the central regions of continents become increasingly arid, CAM and C4 plants are likely to locally increase. Among animals, those adapted for life at high altitudes and latitudes, probably will be pushed to extinction as a result of increased isotherms, with lower altitude and latitude species replacing the species presently living in these environments. Overall, this projected climatic change, should it come to pass, will lead to the massive extinction of species presently living in marginal environments. The great extinction of island endemics apparently resulted from their reduction in energy expenditure with its reduction in reproductive output combined with the human-based increase in mortality. This trend will likely continue with the continued impact of people and the projected increase in sea level. See also: Ecophysiology; Parasitism; Stability versus Complexity.

Further Reading Dehnel A (1949) Studies on the genus Sorex L. Annales Uniwersytet Marii Curie-Skłodowska, C 5: 1–63.

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Heinrich B (1981) Ecological and evolutionary perspectives. In: Heinrich B. (ed.) Insect Thermoregulation, pp. 236–302. New York: Wiley. Iriarte JA, Franklin WL, Johnston WE, and Redford KH (1990) Biogeographic variation in food habits and body size of the American puma. Oecologia 85: 185–190. Jessop TS, Madsen T, Sumner J, et al. (2006) Maximum body size among insular Komodo dragon populations covaries with large prey density. Oikos 112: 422–429. Knutson RM (1974) Heat production and temperature regulation in eastern skunk cabbage. Science 186: 746–747. Lambers H, Chapin FS, III, and Pons TL (1998) Plant Physiological Ecology. New York: Springer. Lillywhite HB and Navas CA (2006) Animals, energy, and water in extreme environments: Perspectives from Ithala 2004. Physiological and Biochemical Zoology 79: 265–273. McNab BK (1971) On the ecological significance of Bergmann’s rule. Ecology 52: 845–854. McNab BK (2002) The Physiological Ecology of Vertebrates: A View from Energetics. Ithaca: Cornell University Press. McNab BK (2006) The energetics of reproduction in endotherms and its implication for their conservation. Integrative and Comparative Biology 46: 1159–1168. Nagy KA, Girard IA, and Brown TK (1999) Energetics of free-ranging mammals, reptiles, and birds. Annual Reviews of Nutrition 19: 247–277. Nagy KA, Odell D, and Seymour RS (1972) Temperature regulation by the inflorescence of Philodendron. Science 178: 1195–1197. Pearson OP and Bradford DF (1976) Thermoregulation of lizards and toads at high altitudes in Peru. Copeia 1976: 155–170. Root T (1988) Energy constraints on avian distributions and abundances. Ecology 69: 330–339. Sondaar PY (1977) Insularity and its effect on mammal evolution. In: Hecht MK, Goody PC, and Hecht BM (eds.) Major Patterns in Vertebrate Evolution, pp. 671–707. New York: Plenum.

Phytoremediation S C McCutcheon, US Environmental Protection Agency, Athens, GA, USA S E Jørgensen, Copenhagen University, Copenhagen, Denmark ª 2008 Elsevier B.V. All rights reserved.

Phytoremediation and Other Biotechnologies Ecological Engineering Genetics and Biochemistry of Phytoremediation and Ecological Engineering Proteomics in Phytoremediation Research

Genetic Engineering Future Directions and Needs State of the Practice Further Reading

Phytoremediation and Other Biotechnologies

algae, cyanobacteria, and fungi, must be involved in the synthesis or maintenance of biomass, or in the direct metabolism, storage, detoxification, or control of contaminants. Glycosylation, occurring in plants and saprophytic fungi but not bacteria, is usually important in direct metabolism, detoxification, and accumulation or storage of pollutants by plants. Glycosylation is a sequestration of contaminant molecules by the addition of a glycosyl group to form a glycoprotein that plant cells can easily

‘Phytoremediation’ is the cleanup or control of wastes, especially hazardous wastes, using green plants. There are many types of phytoremediation, as shown in Table 1, including the use of phreatophytes to control plumes of groundwater contaminants and contaminated vadose zones. Photoautotrophs, including vascular plants, green