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Most evolutionary models focus on isolated traits, but the fitness of an organism depends on the combination of traits that composes its phenotype. Models of coadaptation account for the interaction between thermoregulatory behaviour and thermal physiology. These models cast doubt on a fundamental tenet of the theory of thermal adaptation; specifically, models that ignore coadaptation either predict or assume a close match between an organism's mean body temperature and its thermal optimum for performance. Two evolutionary processes can lead to a mismatch between the body temperature and the thermal optimum. First, time lags for acclimation and deacclimation favour a mismatch to reduce the loss of performance during thermal change. Second, imprecise thermoregulation favours a mismatch to prevent the loss of performance at high temperatures. An explicit focus on the interaction between traits will shed light on these processes and other processes of coadaptation.

Models of thermal adaptation generally ignore selective pressures imposed by the interactions among genotypes. This view should be replaced by the concept of a thermal game, in which the optimal strategy of thermosensitivity, thermoregulation, or acclimation depends on the strategies of other organisms. Models of thermal games predict patterns of adaptation that differ drastically from the patterns generated by traditional optimality models. Natural selection might favour a very low accuracy of thermoregulation when an organism must deal with competitors or predators. The same ecological interactions can shape the evolution of performance curves in surprising ways. For example, competition can cause the thermal optimum to deviate from the mean environmental temperature. Furthermore, predation can cause endless cycles of adaptation in which the thermal optima of predators and prey rarely match their mean temperatures. Equally novel insights will likely emerge from the analysis of other thermal games.

Rates of warming during recent decades have exceeded those experienced during the previous millennia. This anthropogenic climate change has led to advances in organismal phenology, shifts in geographic ranges, and disruptions of ecological interactions. A growing body of evidence underscores the need to consider evolutionary responses to global warming. Both the physiological regulation of phenology and the thermal sensitivity of performance have evolved in warming environments. Nevertheless, quantitative genetic and allelic models suggest that rapid warming will lead to persistent maladaptation and certain extinction. The degree of maladaptation during warming depends on numerous factors, including the stochasticity of temperature, the size of the population, the additive genetic variance, the rate of gene flow, and the interactions between species. Further development of these models could lead to an applied theory of thermal adaptation that more accurately predicts the biological impacts of global warming.

Many animals show unique morphological and behavioural adaptations to desert extremes, while others are able to avoid these by behavioural means. This chapter focuses on patterns of convergent evolution of traits to assess which features represent unique desert adaptations. There are several taxa for which suitable, phylogenetically-controlled analyses have been conducted. This means that the effects of phylogeny, which may be considerable, have been removed. Removing the effects of phylogeny allow one to test whether an adaptation has occurred. For example, a character may be considered a desert adaptation because many desert-dwelling species possess the character, and non-desert-dwelling species do not. However, if there are many desert-dwelling species in a particular part of a clade, then this character may have evolved by chance alone. Select examples from tenebrionid beetles, lizards, birds, and mammals are considered.

This chapter describes both analytic and measurement techniques used in the study of the environmental physiology of amphibians. The first section explores the benefits and pitfalls of utilizing phylogenetic methods to analyze and interpret physiological and morphological data with respect to phylogeny. The remainder of the chapter describes common techniques used for the measurement of temperature, water and ion exchange, cardiovascular physiology, and metabolism.

The maintenance of body temperature is an essential behavior in the homeostatic repertoire orchestrated by central neural circuits. Thermoregulatory pathways optimize cellular and organ function at rest and in response to the demands of behavior, environmental temperature challenges and inflammation, and infectious disease processes. An overview of the functional organization of thermoregulatory mechanisms is presented. This chapter summarizes the research leading to our current understanding of the neural pathways and the neurotransmitter systems through which thermal and pyrogenic afferent signaling alters the activity of thermoregulatory effectors. These effectors include the cutaneous circulation for control of heat loss, the brown adipose tissue, skeletal muscle and the heart for thermogenesis, and the various species-dependent mechanisms of evaporative heat loss. The activation of thermoregulatory effectors is regulated by parallel but distinct, effector-specific, core efferent pathways within the central nervous system that share a common peripheral thermal sensory input.

This chapter provides an overview of the beaver's diving reflex and thermoregulation, with particular emphasis on its evolution from a basic mammalian design into a superb amphibious, semiaquatic animal. It describes the anatomy of the beaver, which betrays the habit of extensive floating on the water surface: the vital air intake and sense organs are arranged so that the nostrils, eyes, and ears extend above the water while the rest of the head and body are submerged. It also explains how the beaver has acquired swimming and diving prowess without losing its ability to walk and even run, dig, and forage on land. Finally, it examines the beaver's thermoregulation in water and on land.

This chapter examines the paleophysiology of nonavian dinosaurs. It describes the physiological and functional aspects of dinosaurs and focuses on two distinct physiological attributes: thermoregulation and aerobic capacity. New evidence pertaining to dinosaur energetics and thermoregulation is examined. The chapter discusses respiratory turbinates, resting metabolic rates, lung structure, ventilation, elevated active metabolic rates, and the relationship between bone microstructure and thermoregulation in nonavian dinosaurs.

From a lizard's perspective, the world is a complex set of landscapes. Physical landscapes change relatively slowly, but changes can be great given enough time. Because lizards cannot regulate their body temperatures physiologically like mammals and birds, the thermal landscape is of particular importance and in many respects, more complex than the physical landscape itself. This chapter discusses how lizards move around in their respective habitats, how they perform their daily activities within constraints of the particular habitat where they live. It examines the physiological responses of lizards, including their locomotor abilities, thermoregulation, and other intra- and interspecific interactions.

This chapter discusses the various aspects of the environment that are important to anoles, as well as the extent to which habitat use shifts through time. Anoles occur in many habitats, elevations, and latitudes, and differ in extent of basking. There are aspects of the environment that vary within and among localities, and to which anoles specialize. This specialization allows anole species to adapt to extreme habitats, and permits sympatric species to coexist while occupying the same structural microhabitat. The chapter discusses two important environmental factors—temperature and moisture—and then examines the effectiveness of microhabitat selection for anole thermoregulation. It also describes remote sensing approaches to investigate the habitat requirements of anoles and ontogenetic and seasonal shifts in habitat use.

This chapter discusses how insects are affected by temperature variations and extremes, and the different adaptations that allow some independence of ambient temperatures (behavioural and physiological thermoregulation) and that facilitate survival in extreme heat or cold. Stresses from water loss are discussed in the context of water balance (excretion and osmoregulation), and focus broadly on the mechanisms that allow survival in environments where water loss may be very high, such as saline lakes and marine habitats. The final section considers some extreme examples of aquatic life stages that can survive almost total dehydration, a form of cryptobiosis. These discussions provide a general description of the stresses and survival strategies, and avoid detailed descriptions of the underlying physiology and biochemistry.

The direct impacts of higher temperatures on birds are manifested over timescales ranging from minutes and hours to years and decades. Over short timescales, acute exposure to high temperatures can lead to hyperthermia or dehydration, which among arid-zone species occasionally causes catastrophic mortality events. Over intermediate timescales of days to weeks, high temperatures can have chronic sub-lethal effects via body mass loss or reduced nestling growth rates, negatively affecting sev eral fitness components. Long-term effects of warming manifested over years to decades involve declining body mass or changes in appendage size. Key directions for future research include elucidating the role of phenotypic plasticity and epigenetic processes in avian adaptation to climate change, examining the role of stress pathways in mediating responses to heat events, and understanding the consequences of higher temperatures for species that traverse hot regions while migrating.

It seems now clear that localizing somatosensory sensations is a relevant factor in the discrimination of where our body begins and where it ends. That is, the sense of touch helps to mark that which is “us” and that what is not. Although it seems somehow straightforward to perceive our arm, hand, leg or face as a part of our body, something that contributes to define who we are as individuals differentiated from the rest of the world, the neural process that allows for this sense of ownership to remain constant, is rather complex. There are situations where body ownership is lost or where external objects are perceived as a part of our own body. This can occur as a consequence of brain damage but also as a result of certain experimental manipulations. In fact, the result of the extant research in this field would seem to suggest that our brain is prepared to integrate in its own circuits additional body parts that are not an anatomical product of genetic coding and that the processing of tactile information plays a major role in leading this process.

The product of natural selection over at least 15 million years is the elongated, slender shape of giraffes that fits the natural habitat giraffes now occupy. What selection pressures operated to produce their shape? Their shape is partly the product of gravity and could have been an accidental by-product of selection for a large body mass and the protection from predation that large size brings, but the prevailing explanation is that their shape confers a browsing advantage. Preferred browse is concentrated at a height easily reached by giraffes but not by other browsers and natural selection would have favored those giraffes that could reach it. An alternative hypothesis is that their shape confers thermoregulatory benefits in addition to improved vigilance. Another hypothesis is that a long neck evolved to counter long legs allowing giraffes to drink surface water. An attractive hypothesis is that their shape is a product of ‘runaway’ sexual selection by females for males with long heavy necks, but analysis of this hypothesis has shown that the morphology of male and female giraffe does not differ. Nevertheless, all these possibilities could have contributed. A consequence of selection for their shape is over-specialization: giraffes seem to be inextricably dependent on a narrow diet, a diet that is subject to the vagaries of climate and competition for resources. The greatest threat to their survival is, therefore, their shape.

This chapter describes the beaver’s biology and physiology, including many unique specialized adaptations to enable them to cope with their semi-aquatic lifestyle, such as diving and digesting bark. The chapter begins with a general description of the beaver body form and structure, including differences between the species. They possess a range of unique features and specialized organs that enable them to survive a semi-aquatic lifestyle, including thick waterproof fur, a cloaca, and various thermoregulation adaptations. Locomotion varies, on land, the beaver is a large, plodding animal that rarely waddles far from the water’s edge. In water they move quickly and dive efficiently and, while potentially not the most agile of swimming animals, spend large amounts of time in the water foraging and maintaining their territory. The beaver tail is quite unique, its form and function are discussed. The beaver’s digestive system is described, including specialized features, e.g. an enlarged caecum ‘fermentation chamber’ designed to accommodate large amounts of complex cellulose such as bark, which is aided by microorganisms in the beaver’s stomach that help in breaking down these substances. The physiology of scent production is also described as chemical communication is significant in these two species. This chapter highlights key features which enable beavers to spend long periods in water and underground especially in prolonged winters.