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Ecology Functional Morphology of Animals
by
Duncan J. Irschick

Introduction

As a field, functional morphology aims to understand how morphological form is related to function in the broadest sense. The goals of functional morphology are twofold. The first goal is to understand whether different body forms and physical structures (e.g., bone dimensions) match in a logical way with the functions that they appear well suited for (e.g., locomotion, feeding), and whether such matching makes sense in an evolutionary and ecological context. A second goal is mechanistic; namely, to understand how basic functions, such as locomotion, occur by examining lower-level components, such as muscles, bones, and heart tissue. However, the field of functional morphology is heterogeneous and has several subfields, each of which has its own history and traditions, and each of which adds generally to the broad goal of relating form to function. These subfields include functional anatomy, biomechanics, ecomorphology, and evolutionary functional morphology. Functional anatomy predominated for many centuries, and it aimed to infer function from structure. While it remains today as a conceptual tool, it has largely been supplanted by direct measurements of animal function. Biomechanics unites the science of material properties and physics to understand animal movement. Ecomorphology represents an infusion of functional morphological techniques into the field of ecology, and it is useful for understanding specializations to different habitats. Finally, evolutionary functional morphology integrates principles of evolutionary theory with functional morphology. Evolutionary functional morphology has blossomed in particular over the last several decades. The field of functional morphology in its present form came fully into existence in the 1950s and 1960s, but underlying ideas about how form relates to function have been in existence at least since the time of Aristotle. An exact timeline is challenging, but the field was dominated for many years by anatomists, who inferred how form related to function. The advent of technological innovations in the 1950s and 1960s that allowed the visualization of movement and the monitoring of internal structures such as muscles allowed the field to mature such that both form and function could be empirically studied. Whereas research in the 1960s and 1970s was limited to a few model species that could be examined using only a few techniques, the modern field employs a wide array of techniques, both in the field and in the laboratory, and examines many kinds of animal species. The field has evolved from simple descriptions of external form, anatomy, or movement to highly detailed empirical analyses of body movements using high-speed video (kinematics), and force plates (kinetics). Functional morphology is inherently comparative, and it examines many kinds of species (e.g., birds, lizards, mammals) that occur in different environments (e.g., aquatic, terrestrial).

General Overviews

There is no single original classic work, for the field of functional morphology is heterogeneous and was cobbled together across many years by many independent researchers. However, several early syntheses are notable. Gans 1974 is an influential early source that explained the overarching goals of biomechanics, a subfield of functional morphology. R. McNeill Alexander has written many seminal overviews, including Alexander 1992, which is a well-written and readable account of biomechanics. Hildebrand, et al. 1985 is an edited volume that stands as a landmark in the field by providing a coherent and practical set of chapters written by experts on different functions (e.g., climbing, locomotion). Lauder 1995 is a book chapter that nicely explains why we expect form and function should (or should not) be related among individuals or among species. Two relatively recent and thorough books on locomotion, Alexander 2003 and Biewener 2003, encapsulate many of the techniques and concepts that are relevant for other functions, such as feeding. Irschick and Henningsen 2009 provides a recent overview of the state of the field, and while concise, it provides several case studies that are exemplars of the modern approach.

  • Alexander, R. McNeill. 1992. Exploring biomechanics: Animals in motion. New York: Scientific American Library.

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    This book covers all kinds of animal movements, ranging from running to flying, and answers some of the most basic mysteries surrounding animal movement, such as how cheetahs can run so fast, or whether flying lizards can actually “fly.”

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  • Alexander, R. McNeill. 2003. Principles of animal locomotion. Princeton, NJ: Princeton Univ. Press.

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    Provides an extensive source of references on all aspects of locomotion, but focuses on the mechanistic and biomechanical determinants of locomotion rather than the ecological or evolutionary causes.

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  • Biewener, Andrew A. 2003. Animal locomotion. Oxford: Oxford Univ. Press.

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    This book differs from Alexander 2003 in being more focused on muscles, nerves, and bones as important elements driving locomotion. It has an excellent chapter on the neural basis of locomotion that is worth reading.

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  • Gans, Carl. 1974. Biomechanics: An approach to vertebrate biology. Ann Arbor: Univ. of Michigan Press.

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    One of the first books to comprehensively synthesize the range of techniques used in biomechanics, such as EMGs. The author is greatly interested in reptiles, and they are heavily represented in this book.

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  • Hildebrand, Martin, Dennis F. Bramble, Karl F. Liem, and David B. Wake. 1985. Functional vertebrate morphology. Cambridge, MA: Belknap Press of Harvard Univ. Press.

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    A classic compendium of chapters that covers topics ranging from climbing to flight, each written by an expert. While some chapters tend to infer function from form, this remains a must-read for any budding functional morphologist.

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  • Irschick, Duncan J., and Justin P. Henningsen. 2009. Functional morphology: Muscles, elastic mechanisms, and animal performance. In Princeton guide to ecology. Edited by Simon Levin, 27–37. Princeton, NJ: Princeton Univ. Press.

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    A concise (10-page) book chapter that provides key definitions for terms such as performance and kinematics, and provides several key examples that describe the range of techniques used in functional morphology, such as studies of flight kinematics in bees, and X-rays of breathing in lizards.

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  • Lauder, George V. 1995. On the inference of function from structure. In Functional morphology in vertebrate paleontology. Edited by Jeffrey J. Thomason, 1–18. Cambridge, UK: Cambridge Univ. Press.

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    A conceptual book chapter that argues that inferring function from structure has some shortcomings; a valuable cautionary paper.

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Journals

More than ten journals publish research in the broader field of functional morphology. Some examples include The Journal of Experimental Biology, Physiological and Biochemical Zoology, and Functional Ecology. While early studies in this field focused on basic descriptions of anatomy and function, usually with limited taxonomic sampling and modest experimental sample sizes, more recent work employs a more comparative approach and is often experimentally robust. Further, technological developments have enabled researchers to study animal function both in the field and in the laboratory. Thus, some journals publish research at the interface between traditional functional morphology and animal ecology, such as Functional Ecology and Physiological and Biochemical Zoology. Other journals focus on anatomy, such as the Journal of Morphology and The Anatomical Record.

Defining Functional Morphology

Irschick and Henningsen 2009 provides a recent definition and explanation of functional morphology. Lauder 1995 also explains the basic goals and concepts that underlie this field. An older but useful discussion of this field can be found in DeVree and Gans 1989. Functional morphology attempts to explain the morphological diversity of organisms, both within and among species, in the context of their abilities to perform basic functions, such as to run, jump, or crawl. It applies a mechanistic and often experimental approach to determining the underlying causes of variation in body form by examining variation in traits such as muscles, tendons, bones, and other tissues. Other goals of functional morphology include understanding how variation in morphology and function explain variation in ecology, otherwise known as ecomorphology. For a more ecological perspective on functional morphology, Wainwright 1991 is a good place to start, as it outlines the basic principles of ecomorphology. Alexander 1975 is a concise and readable account of biomechanics, a subfield that aims to understand animal body form through the ideas of mechanics and physics. The field of functional morphology can also be understood through Krogh and Weis-Fogh 1951, an early work that clearly explains how respiratory surfaces and flight are related in locusts.

  • Alexander, R. McNeill. 1975. Biomechanics. New York: Halsted Press.

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    A short and readable book suitable for the layperson. It is not comprehensive in its examples or approach, but rather introduces concepts that can be explored in more extensive books.

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  • De Vree, Fritz, and Carl Gans. 1989. Functional morphology of the feeding mechanisms in lower tetrapods. In Trends in vertebrate morphology: Proceedings of the 2nd International Symposium on Vertebrate Morphology, Vienna, 1986. Fortschritte der Zoologie 35. Edited by Heinz Splechtna and Helge Hilgers, 115–127. Stuttgart: Gustav Fischer Verlag.

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    Provides a review of feeding in lower tetrapods, and is a good introduction to various techniques used by functional morphologists to understand muscle function.

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  • Irschick, Duncan J., and Justin Henningsen. 2009. Functional morphology: Muscles, elastic mechanisms, and animal performance. In Princeton guide to ecology. Edited by Simon Levin, 27–37. Princeton, NJ: Princeton Univ. Press.

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    This book chapter explains the goals of functional morphology and explains various terms, such as function and performance.

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  • Krogh, August, and Torkel Weis-Fogh. 1951. The respiratory exchange of the desert locust (Schistocerca gregaria) before, during and after flight. Journal of Experimental Biology 28:344–357.

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    The classic paper reveals the interface between morphological design and key aspects of function, and it helped define the field of functional morphology.

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  • Lauder, George V. 1995. On the inference of function from structure. In Functional morphology in vertebrate paleontology. Edited by Jeffrey J. Thomason, 1–18. Cambridge, UK: Cambridge Univ. Press.

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    Conceptual paper that outlines the basic limits of functional morphology without empirical data on function.

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  • Wainwright, Peter C. 1991. Ecomorphology: Experimental functional anatomy for ecological problems. American Zoologist 31.4: 680–693.

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    A paper that greatly broadens the paradigm of ecomorphology by elaborating on the key role of animal function that can be linked to morphology and ecology.

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Foundational Works

There are many excellent early foundational contributions, but several are noteworthy for their technical innovation or for the introduction of key concepts. The early history of the field of functional morphology was dominated by anatomists who made functional inferences. Borelli 1989 was originally published in 1680 and was one of the earliest papers to explain the basic logic of how structures can produce forces and movements in organisms through simple lever mechanics. Though speculative by today’s standards, many of the ideas still hold value today. Dullemeijer 1974 was a relatively early conceptual paper that explained methods for understanding the functions of animal morphology. As the importance of ecology emerged in the 1960s, functional morphologists became interested in whether morphological traits could be considered linked to ecology, and thus be adaptive, a mindset that was explained in Bock and Von Wahlert 1965. The idea of elastic mechanisms, a key idea that persists today in functional morphology, is exemplified in the seminal paper Bennet-Clark and Lucey 1967, which examined how the jump of the flea is amplified by elastic elements in their joints. This paper was also a harbinger of the field of biomaterials, the study of the biological function of living materials. Bramble and Carrier 1983 showcased a mechanistic approach for understanding function in living animals by demonstrating the coupling of the respiratory system and movement in mammals. One of the most central questions in functional morphology is the energetic cost of movement, and Taylor and Heglund 1982 reviews classic experiments that showed how the cost of locomotion changes regularly with animal size. The role of animal size and its influence on animal movement, also known as allometry, has been a central question in functional morphology, and Emerson 1978 is an influential paper that connected the process of ontogeny with animal function. Hill 1950 is widely cited and discussed because of its bold, yet poorly understood trade-off between the different components that contribute to jumping. Webb 1976 presented a classic example of how predator-prey interactions are likely to influence performance ability in fish. Wainwright, et al. 1978 showed the power of biomaterials by explaining how shark skin has a clear function that aids the shark’s swimming abilities, a contribution that went a long way towards showing the power of biomimetics. Much research has also focused on movements in fluids in both vertebrates and invertebrates, and Daniel 1984 is a good place to start on this topic.

  • Bennet-Clark, Henry C., and Eric C. A. Lucey. 1967. The jump of the flea: A study of the energetics and a model of the mechanism. Journal of Experimental Biology 47:59–76.

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    A classic study that was among the first to clearly show the role of biomaterials that act as performance enhancers, in this case for jumping in fleas.

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  • Bock, Walter J., and Gerd von Wahlert. 1965. Adaptation and the form-function complex. Evolution 19.3: 269–299.

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    A conceptual paper that explains the concept of “biological role” in terms of the utility of morphological traits, and how such traits can be examined in a functional context to test ideas about adaptation.

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  • Borelli, Giovanni A. 1989. On the movement of animals. Translated by Paul Maquet. Berlin: Springer-Verlag.

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    Originally published in Italian in 1680 as De motu animalium. One of the earliest explanations of how animal structures could produce force through basic mechanical principles.

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  • Bramble, Dennis M., and David R. Carrier. 1983. Running and breathing in mammals. Science 219.4582: 251–256.

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    A classic study that shows clearly the coupled mechanism of running and breathing, and that represents a major advance in our understanding of respiration.

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  • Daniel, Thomas L. 1984. Unsteady aspects of aquatic locomotion. American Zoologist 24.1: 121–134.

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    An influential review that examines the physical principles that influence movement in various kinds of aquatic animals.

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  • Dullemeijer, Piet. 1974. Concepts and approaches in animal morphology. Assen, The Netherlands: Van Gorcum.

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    A conceptual paper that explains why researchers should study animal morphology, as well as some of the logical principles that link form to function.

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  • Emerson, Sharon B. 1978. Allometry and jumping in frogs: Helping the twain to meet. Evolution 32.3: 551–564.

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    This paper is a conceptual and empirical advance because it addresses how animal locomotor performance can be expected to change with body size, and what deviations from this expectation imply in an evolutionary context.

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  • Hill, Archibald V. 1950. The dimensions of animals and their muscular dynamics. Scientific Progress 38.150: 209–230.

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    Hill’s famous and well-cited paper outlines some basic trade-offs in jumping based on how muscles function; the paper has ignited many debates about how animal size and form influence locomotion.

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  • Taylor, Charles R., and Norm C. Heglund. 1982. Energetics and mechanics of terrestrial locomotion. Annual Review of Physiology 44:97–107.

    DOI: 10.1146/annurev.ph.44.030182.000525Save Citation »Export Citation »E-mail Citation »

    This seminal review encapsulates some of the key work of the famous and late Charles Taylor, who examined the basic determinants of animal energetics, such as body size and gait.

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  • Wainwright, Steven A., Frank Vosburgh, and John H. Hebrank. 1978. Shark skin: Function in locomotion. Science 202.4369: 747–749.

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    One of the first studies to highlight the value of biomaterials for enhancing locomotion; also a harbinger for future biomimetic work.

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  • Webb, Paul W. 1976. The effect of the fast-start performance of rainbow trout Salmo gairdneri and a consideration of piscivorous predator-prey interactions. Journal of Experimental Biology 65:157–177.

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    This paper examines the potential for interaction between predators and prey, and how predators can act as a powerful selective force influencing animal locomotion.

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Contemporary Views

Functional morphology made a shift from interpretative and descriptive studies of anatomy to empirical measurements of animal function in the period between 1950 and 1980, although the visualization of animal movement was pioneered by Eadweard Muybridge in the late 1800s, and later recognized for its scientific value. The study of anatomical structure has remained and flourished over the last fifty or sixty years, but it has increasingly become integrated with studies of animal function. Research by Charles Taylor and his students was formative in expanding this paradigm to include animal physiology, as exemplified in Hoyt and Taylor 1981, which explains gaits in horses through an energetic perspective. The 1970s were a formative time in evolutionary biology, and the publication of Gould and Lewontin 1979, which examines the role of constraints on morphological traits, also had a strong influence on the field of functional morphology. The advent in the 1960s of phylogenetic methods for building phylogenetic trees also influenced functional morphology. Several notable papers explain this evolutionary approach, including Lauder 1982 and Liem 1973. Around the same time, there was increasing integration of ecology and functional morphology, which was ultimately useful for both understanding patterns of community structure and testing broader ideas about adaptation. This emerging field of ecomorphology is showcased in Karr and James 1975. A more recent view of ecomorphology can be found in the edited volume Wainwright and Reilly 1994. The advent of greater technical expertise over the last twenty or so years has allowed ever more precise formulations of various theories, particularly in regard to how key structural elements, such as bones, muscles, or tendons, function. The edited volume Biewener 1992 is a good place to start in understanding the range of techniques that are still widely used today.

  • Biewener, Andrew A., ed. 1992. Biomechanics: structures and systems, a practical approach. Practical Approach series, Oxford: Oxford Univ. Press.

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    A practical edited volume that covers the range of techniques used by functional morphologists, from force plates to kinematic analysis. Provides actual methods for constructing devices such as force plates.

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  • Gould, Steven J., and Richard C. Lewontin. 1979. The spandrels of San Marco and the Panglossian paradigm: A critique of the adaptationist programme. Proceedings of the Royal Society B: Biological Sciences 205:581–598.

    DOI: 10.1098/rspb.1979.0086Save Citation »Export Citation »E-mail Citation »

    A classic paper that explains the basic importance of constraints in channeling morphological and functional traits. A must-read, as it is still highly relevant today.

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  • Hoyt, Donald F., and Charles R. Taylor. 1981. Gait and the energetics of locomotion in horses. Nature 292:239–240.

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    One of the first papers to explain how gaits act much like gears in a car in allowing animals to minimize energy use. A good example of the emerging integration of physiology and functional morphology in the 1980s.

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  • Karr, James R., and Frances C. James. 1975. Eco-morphological configurations and convergent evolution in species and communities. In Ecology and evolution of communities. Edited by Martin L. Cody and Jared M. Diamond, 258–291. Cambridge, MA: Harvard Univ. Press.

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    A must-read for any functional morphologist and community ecologist because it explains how ecomorphology is a tool for understanding both community structure and adaptation, although its emphasis on functional traits is limited.

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  • Lauder, George V. 1982. Historical biology and the problem of design. Journal of Theoretical Biology 97:57–67.

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    Lauder is one of the strongest proponents of incorporating history into functional studies, and this paper is a nice gateway for this topic because of the clear writing. This paper also discusses the role of constraints, in a more explicitly functional context.

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  • Liem, Karel F. 1973. Evolutionary strategies and morphological innovations: Chiclid pharyngeal jaws. Systematic Zoology 22.4: 425–441.

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    A novel paper for its time because it argued that functional and morphological diversity could dramatically influence how adaptive radiations occur, by either closing off or opening new options for accessing niches.

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  • Wainwright, Peter C., and Stephen M. Reilly, eds. 1994. Ecological morphology: Integrative organismal biology. Chicago: Univ. of Chicago Press.

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    A wonderful resource, and the bible for all ecomorphologists. It has a mix of chapters that range from those advocating inferring function from morphology to those that argue functional studies are crucial. Contains many papers with empirical data.

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Technical Innovation

The emergence of technical improvements has guided the field of functional morphology in significant ways. Basmajian and Stecko 1962 was an early paper that demonstrated the feasibility of electromyograms (EMGs), which allowed researchers to examine in real time how (and which) muscles are used during movements, thus ushering in a new era of muscle physiology that spawned numerous papers and analytical methods. The invention of sonomicrometry (Griffiths 1987) provided an additional tool that allowed researchers to understand how changes in muscle length occurred during movements. Improvements in high-speed camera technology have enabled researchers to “slow down” nearly any movement, even those that seemed invisible to human eyes, such as the flight of a fly. Eadweard Muybridge was an early pioneer of the fast-stop camera, which he used to document large numbers of human and animal movements, and Shimamura 2002 is a good account of his contributions. High-speed video has been integrated with computer software to allow the calculation of 2-D and 3-D body and joint angles, thus allowing researchers to empirically measure and compare complex animal movements, such as the rotation of limb joints. These techniques are explained in Biewener and Full 1992. Cavagna 1975 is an important paper showing how strain gauges can be used to measure kinetic forces generated by movements. This was a boon for understanding bone function (as strain gauges could be placed on bones), and also the general forces (kinetics) used by organisms during locomotion. Other visualization techniques have played an important role in describing internal anatomy, such as X-rays, CT scanning, and X-ROM. Brainerd 2007 gives an explanation of more recent internal visualization techniques. There have also been innovations for understanding animal flight, such as the use of gases (Dudley 1995) or flight tunnels for visualizing flight in various kinds of animals, such as bees or flies.

  • Basmajian, John V., and George Stecko. 1962. A new bipolar electrode for electromyography. Journal of Applied Physiology 17.5: 849.

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    One of the first papers to demonstrate the technique of electromyography for measuring muscle function.

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  • Biewener, Andrew A., and Robert J. Full. 1992. Force platform and kinematic analysis. In Biomechanics structures and systems: A practical approach. Edited by Andrew A. Biewener, 45–73. Oxford: Oxford Univ. Press.

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    This chapter in an edited volume explains in practical terms how to perform 2-D and 3-D analysis and provides a great deal of background on the math behind such transformations. Further, the authors discuss kinetic analyses and offer some aid for the construction of force plates.

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  • Brainerd, Elizabeth L. 2007. 4D-imaging methods in vertebrate morphology. Journal of Morphology 268.12: 1052–1053.

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    A recent paper that shows emerging multiple-dimension technology for visualizing hard tissue movements, such as bones, during functions such as feeding or locomotion.

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  • Cavagna, Giovanni A. 1975. Force platforms as ergometers. Journal of Applied Physiology 39.1: 174–179.

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    One of the first papers to explain how strain gauges can be used to measure whole-body forces when integrated into a force platform.

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  • Dudley, Robert. 1995. Extraordinary flight performance of orchid bees (Apidae: Euglossini) hovering in heliox (80% He/20% O2). Journal of Experimental Biology 198:1065–1070.

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    A good example of modern innovations for understanding the flight of animals, such as invertebrates, in this case by using different mixtures of gases to alter flight conditions.

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  • Griffiths, Roger G. 1987. Ultrasound transit time gives direct measurement of muscle fibre length in vivo. Journal of Neuroscience Methods 21.2–4: 159–165.

    DOI: 10.1016/0165-0270(87)90113-0Save Citation »Export Citation »E-mail Citation »

    Griffiths’s paper explains the use of sonomicrometry, which allows direct measurements of muscle length changes in living organisms.

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  • Shimamura, Arthur P. 2002. Muybridge in motion: Travels in art, psychology, and neurology. History of Photography 26:341–350.

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    This reading provides a useful and readable overview of the life of Eadweard Muybridge, who was a pioneering figure in the realm of stop-motion photography. It also discusses his work in an artistic and psychological framework.

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Subfields of Functional Morphology

This section is divided into the following subsections: Functional Anatomy, Biomechanics, Ecomorphology, and Evolutionary Functional Morphology.

Functional Anatomy

Functional anatomy was the dominant mode of understanding animal function for hundreds of years, but it has largely been supplanted by direct measurements of animal function. This subfield infers animal function from the overall anatomical structures and arrangements of structures, a practice that is generally frowned upon today. For example, Leonardo da Vinci was very interested in anatomy and its potential link to function (Mathé 1978). Appel 1987 provides a valuable historical account of the debates of anatomists such as Georges Cuvier. Hildebrand 1982 is an influential paper that explains this tradition, just as new tools were emerging to study animal function. Lauder 1995 and Lauder 1996 clearly explain the pitfalls of this approach. Russell 1982 provides a valuable history of how functional anatomy has evolved to a more empirical tradition. Ashley-Ross and Gillis 2002 is a more recent historical account that explains the traditions and people involved in functional anatomy.

  • Appel, Toby A. 1987. The Cuvier–Geoffrey debate: French biology in the decades before Darwin. Oxford: Oxford Univ. Press.

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    A valuable account of the debates between Georges Cuvier and Etienne Geoffroy Saint-Hilaire, two French anatomists who were pioneers in the realm of functional anatomy in the early 1800s.

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  • Ashley-Ross, Miriam A., and Gary B. Gillis. 2002. A brief history of vertebrate functional morphology. Integrative and Comparative Biology 42.2: 183–189.

    DOI: 10.1093/icb/42.2.183Save Citation »Export Citation »E-mail Citation »

    This is a brief but detailed historical account of the history of vertebrate functional morphology, and is notable for its rare and useful detail on the early history of this field.

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  • Hildebrand, Milton. 1982. Analysis of vertebrate structure. 2d ed. New York: Wiley.

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    Hildebrand was a pioneer who moved the field toward a more functional and empirical mindset, although some of his works, including this one, still emphasized inferring function from form. This book is recommended more for its historical value than for providing a set of research tools for students.

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  • Lauder, George V. 1995. On the inference of function from structure. In Functional morphology in vertebrate paleontology. Edited by Jeffrey J. Thomason, 1–18. Cambridge, UK: Cambridge Univ. Press.

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    This is a conceptual paper by Lauder that cautions against inferring function from form, and explains the pitfalls of the early functional anatomical approach performed for many centuries.

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  • Lauder, George V. 1996. The argument from design. In Adaptation. Edited by Michael R. Rose and George V. Lauder, 55–92. San Diego, CA: Academic Press.

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    This paper examines alternative models of morphological designs and how current forms may not be optimal, but may be constrained by evolutionary history or development.

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  • Mathé, Jean. 1978. Leonardo da Vinci: Anatomical drawings. Translated by David Macrae. New York: Crown.

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    Contains a number of drawings of anatomy from Leonardo da Vinci that showcase his artistic and functional knowledge of structure.

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  • Russell, Edward S. 1982. Form and function: A contribution to the history of animal morphology. 2d ed. Chicago: Univ. of Chicago Press.

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    Russell provides an overview of how biologists should study basic relationships between form and function to understand the process of evolutionary specialization.

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Biomechanics

Biomechanics is a subfield within the broader field of functional morphology. While the goals of the latter are to broadly understand the relation between form and function, the goals of the former are more specific. Biomechanics applies the principles of engineering and physics to animal movement. Alexander 1975 is an early readable account of this field, and Gans 1974 is a comprehensive book that is more suited to the specialist. The technical aspects of biomechanics are covered in the edited volume Biewener and Full 1992 (cited under Technical Innovation). Locomotion is perhaps the most widely studied area within biomechanics, and Biewener 2003 is a comprehensive source. Two good examples of the breadth and value of biomechanics for understanding morphological structure and function are Biewener 1989, which examines the scaling of mammalian limbs in relation to posture, and Toro, et al. 2004, which examines how lizards jump relative to an “optimal” expectation. Vogel 2003 is a read well-suited for the layperson, about the world of comparative biomechanics. Wainwright, et al. 1976 is an older but still valuable entry into the world of biomaterials, or the study of how biological materials allow animals to function. The field of biomaterials has become increasingly integrated within the field of biomechanics, such as in studies of elastic mechanisms that power locomotion, as shown by animal tendons in large ungulates such as kangaroos. While these references primarily focus on terrestrial locomotion, the field of biomechanics has also proven valuable for understanding animal flight, such as in birds or in insects. The technical prowess of some flight studies can be clearly seen in Fry, et al. 2003, in which mechanical testing and kinematics are used to examine how flight is controlled in fruit flies.

  • Alexander, R. McNeill. 1975. Biomechanics. New York: Halsted Press.

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    A concise, simple, and readable introduction to biomechanics. While not comprehensive, it provides some new data that are used to demonstrate key concepts such as elastic mechanisms and how limbs produce force. Also explains the value of biomaterials.

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  • Biewener, Andrew A. 1989. Scaling body support in mammals: Limb posture and muscle mechanics. Science 245.4913: 45–48.

    DOI: 10.1126/science.2740914Save Citation »Export Citation »E-mail Citation »

    This is perhaps Biewener’s most significant work, showing how evolutionary changes in limb posture in mammals lead to differences in bones, muscles, and posture. Novel for its integration of evolution and biomechanics.

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  • Biewener, Andrew A. 2003. Animal locomotion. Oxford: Oxford Univ. Press.

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    A comprehensive and mechanistic analysis of locomotion in both vertebrates and invertebrates. It has several chapters devoted to biomechanical themes.

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  • Fry, Steven N., Rosalyn Sayaman, and Michael H. Dickinson. 2003. The aerodynamics of free-flight maneuvers in Drosophila. Science 300.5618: 495–498.

    DOI: 10.1126/science.1081944Save Citation »Export Citation »E-mail Citation »

    A good example of the biomechanical techniques used to understand flight in small invertebrates, in this case fruit flies. Notable for its technical prowess in understanding movement at very small and rapid scales.

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  • Gans, Carl. 1974. Biomechanics: An approach to vertebrate biology. Ann Arbor: Univ. of Michigan Press.

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    A good overview of the early state of biomechanics prior to the advent of key technological advances in video, kinetic, and kinematic analysis.

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  • Toro, Esteban, Anthony Herrel, and Duncan J. Irschick. 2004. The evolution of jumping performance in Caribbean Anolis lizards: Solutions to biomechanical trade-offs. American Naturalist 163.3: 844–856.

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    An empirical paper that shows the interface among behavior, evolution, and the biomechanics of jumping in Anolis lizards. Draws heavily from biomechanical theory about how jumping occurs, and applies an optimality criterion.

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  • Vogel, Steven. 2003. Comparative biomechanics: Life’s physical world. Princeton, NJ: Princeton Univ. Press.

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    A humorous and at times whimsical view of animal function. Also remarkably detailed and comprehensive. An extremely valuable source.

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  • Wainwright, Steven A., William D. Biggs, John D. Currey, and John M. Gosline, eds. 1976. Mechanical design in organisms. New York: John Wiley.

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    An early but still very useful and accurate book, with chapters on different kinds of biomaterials. Remarkably detailed and highly useful for any functional morphologist who wants an introduction to the interface between materials science and biology.

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Ecomorphology

Ecomorphology arose as a tool to understand patterns of community structure, and to enable stronger tests of whether a morphological trait is adaptive. The basic premise of adaptation is that animals should display morphological traits that are well suited to their environments. The influence of this approach can be seen in Williams 1983, which explains how the adaptive radiation of Anolis lizards, now considered a classic example of an adaptive radiation, can be understood through the lens of ecomorphology. Much of the classic ecomorphology work has been conducted on birds, and Karr and James 1975, which examines how bird communities have likely converged in different regions of the world, is a good place to start. Wainwright 1991 outlines the basic principles of ecomorphology and focuses on empirical functional studies rather than inferences from morphology. Two good reviews are Alexander 1988 and Wainwright and Reilly 1994. The former is useful for its theoretical approach to the field, whereas the latter edited volume was written when the field of ecomorphology had arguably reached its apex. This book was also valuable because it started a transformation from simple morphology-ecology correlations to studies of animal function that can be linked to morphology and ecology. Many studies have shown that morphology alone may not be a good predictor of animal function. Therefore, the modern incantation of this field has evolved toward a balanced integration of morphology, function, and ecology, suggesting that the name itself is misleading.

  • Alexander, R. McNeill. 1988. The scope and aims of ecological morphology. Netherlands Journal of Zoology 38.1: 3–22.

    DOI: 10.1163/156854288X00012Save Citation »Export Citation »E-mail Citation »

    Alexander has written about nearly every aspect of functional morphology, and ecomorphology is no exception. Here he explains the basic tenets of this field, but is less focused on community ecology.

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  • Karr, James R., and Frances C. James. 1975. Eco-morphological configurations and convergent evolution in species and communities. In Ecology and evolution of communities. Edited by Martin L. Cody and Jared M. Diamond, 258–291. Cambridge, MA: Harvard Univ. Press.

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    A seminal paper in ecomorphology, as it explains the role of community ecology and of adaptation at the species level. Valuable for both functional morphologists and ecologists.

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  • Wainwright, Peter C. 1991. Ecomorphology: Experimental functional anatomy for ecological problems. American Zoologist 31.4: 680–693.

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    Peter Wainwright’s prelude to Wainwright and Reilly 1994. He outlines the basic ideas of moving beyond simple morphology in studies of ecomorphology, and includes empirical functional data.

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  • Wainwright, Peter C., and Steven M. Reilly, eds. 1994. Ecological morphology: Integrative organismal biology. Chicago: Univ. of Chicago Press.

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    This is a must-read for ecomorphologists, and includes chapters from most of the major figures in the field at the time on many different topics, ranging from whether functional studies are needed to studies of locomotion in lizards.

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  • Williams, Ernest E. 1983. Ecomorphs, faunas, island size, and diverse end points in island radiations of Anolis. In Lizard ecology: Studies of a model organism. Edited by Raymond B. Huey, Eric C. Pianka, and Thomas W. Schoener, 326–370. Cambridge, MA: Harvard Univ. Press.

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    A good example of the influence of ecomorphology. The genus Anolis has been widely cited as a model of adaptive radiation, and this paper was important in establishing correlations between ecology and morphology as the most conspicuous pattern defining this group. Little information about function is presented, but later studies fill this void.

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Evolutionary Functional Morphology

The phylogenetic revolution that profoundly influenced evolutionary biology did not leave the field of functional morphology untouched, although this field retains less of an evolutionary focus than other fields. Some of the early research integrating evolution and functional morphology occurred at the interface of physiology, especially in relation to how morphology and other traits change with size (scaling), for which Calder 1984 is a definitive text. Lauder 1982 was among the first works to carefully explain the important role of history in understanding functional traits. The role of functional traits is also important in the context of key innovations, which are structures or properties that can enhance speciation or morphological diversification. This idea was explained in Liem 1973, which examines the role of the anatomy of the Chiclid fish jaw, and its potential role in enhancing diversity in these fish. This idea has continued to gain traction with time, as seen in Konow, et al. 2008. More recently, some authors have argued for more explicitly designed comparative studies that examine a wide range of taxa that vary in their morphological structure and habitat use. Contemporary work has often focused on the interface between evolutionary diversity and body structure, and most of this work is on fish—including Alfaro, et al. 2005. However, other reviews point toward the interface among evolution, behavior, and ecology, and the importance of an integrated research plan for functional morphology, which is reviewed in Wake 1982 and Irschick 2002. Wake 1982 focuses on the integration between evolution and functional morphology, whereas Irschick 2002 also incorporates information about behavior and animal ecology.

  • Alfaro, Michael E., Daniel I. Bolnick, and Peter C. Wainwright. 2005. Evolutionary consequences of many-to-one mapping of jaw morphology to mechanics in labrid fishes. American Naturalist 165.6: E140–E154.

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    An empirical study that links the evolutionary diversity of fish clades with the morphological diversity of their jaws. While it does not contain functional data per se, it remains valuable for demonstrating an evolutionary approach.

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  • Calder, William A. 1984. Size, function, and life-history. Cambridge, MA: Harvard Univ. Press.

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    A seminal book that integrates the life-history traits of animals and their body size, a field otherwise known as scaling. Also includes a great deal of physiological data, but it can be considered an early pioneering paper in terms of advocating an evolutionary approach.

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  • Irschick, Duncan J. 2002. Evolutionary approaches for studying functional morphology: Examples from studies of performance capacity. Integrative and Comparative Biology 42.2: 278–290.

    DOI: 10.1093/icb/42.2.278Save Citation »Export Citation »E-mail Citation »

    A review that explains how researchers can integrate both ecological and evolutionary data into studies of functional morphology. All of the examples are drawn from lizards.

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  • Konow, Nikolai, David R. Bellwood, Peter C. Wainwright, and Andrew M. Kerr. 2008. Evolution of novel jaw joints promote trophic diversity in coral reef fishes. Biological Journal of the Linnean Society 93.3: 545–555.

    DOI: 10.1111/j.1095-8312.2007.00893.xSave Citation »Export Citation »E-mail Citation »

    Another example of an evolutionary approach as applied to fish jaws. Argues that evolutionary innovations can allow some clades to diversify at greater levels, and applies a more empirical approach than Liem 1973.

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  • Lauder, George V. 1982. Historical biology and the problem of design. Journal of Theoretical Biology 97.1: 57–67.

    DOI: 10.1016/0022-5193(82)90276-4Save Citation »Export Citation »E-mail Citation »

    Lauder has written extensively on the interface between evolution and functional morphology, and this was one of his first papers that laid out the confounding role of history, but also the opportunities that this pattern presented.

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  • Liem, Karel F. 1973. Evolutionary strategies and morphological innovations: Chiclid pharyngeal jaws. Systematic Zoology 22.4: 425–441.

    DOI: 10.2307/2412950Save Citation »Export Citation »E-mail Citation »

    This classic paper tests the idea of key innovations in the context of functional morphology by linking morphological diversity and evolutionary innovations in jaw morphology.

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  • Wake, David B. 1982. Functional and evolutionary morphology. Perspectives in Biology and Medicine 25.4: 603–620.

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    This is representative of the early work of David Wake, who has integrated developmental biology, functional morphology, and evolution through his work on salamander development and feeding.

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Biomimetics

The applications of functional morphology are increasingly becoming evident in human-made robots, which represent the realm of biomimetics, or the use of biological design to guide synthetic design. Early robotic designs mimicked human motions, with limited success, but much attention has been devoted to the creation of robotic designs that mimic animals, using models such as snakes, flies, birds, and bats, among others. While this field has taken off since 2000, some early work explained the value of biomimetics, such as Schmitt 1969. A good example of this approach is the international effort to design synthetic gecko setae to enable dry adhesion, which is summarized nicely in Arzt 2006. An overview of the principles of biomimetics can be found in Vincent, et al. 2006.

  • Arzt, Eduard. 2006. Biological and artificial attachment devices: Lessons for materials scientists from flies and geckos. Materials Science and Engineering C: Biomimetic and Supramolecular Systems 26.8: 1245–1250.

    DOI: 10.1016/j.msec.2005.08.033Save Citation »Export Citation »E-mail Citation »

    A recent review of the state of the quest for a synthetic dry adhesive based on lizard or fly morphology. It reveals that the search has so far met only limited success, with little evidence for a powerful human-scale synthetic adhesive.

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  • Schmitt, Otto. 1969. Some interesting and useful biomimetic transforms. In Proceedings of the Third International Biophysics Congress, Boston, Mass, 29 Aug–3 Sept 1969, 297. Cambridge: Massachusetts Institute of Technology.

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    An early paper that briefly explains the potential for biomimetic design from certain animal models.

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  • Vincent, Julian F. V., Olga A. Bogatyreva, Nikolaj R. Bogatyrev, Adrian Bowyer, and Anja-Karina Pahl. 2006. Biomimetics: Its practice and theory. Journal of The Royal Society Interface 3.9: 471–482.

    DOI: 10.1098/rsif.2006.0127Save Citation »Export Citation »E-mail Citation »

    A review of the theory of biomimetics, and the pitfalls and promise of it. It is not extensive in covering some of the most intensive areas, such as gecko adhesion, but it is a good place to start for those interested in a review of field.

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LAST MODIFIED: 05/23/2012

DOI: 10.1093/OBO/9780199830060-0034

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