View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by UNL | Libraries University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Papers in Natural Resources Natural Resources, School of May 2003 Ecomorphology of Bats: Comparative and Experimental Approaches Relating Structural Design to Ecology Sharon M. Swartz Brown University, [email protected] Patricia W. Freeman University of Nebraska-Lincoln, [email protected] Elizabeth F. Stockwell Dalhousie University, [email protected] Follow this and additional works at: https://digitalcommons.unl.edu/natrespapers Part of the Natural Resources and Conservation Commons Swartz, Sharon M.; Freeman, Patricia W.; and Stockwell, Elizabeth F., "Ecomorphology of Bats: Comparative and Experimental Approaches Relating Structural Design to Ecology" (2003). Papers in Natural Resources. 10. https://digitalcommons.unl.edu/natrespapers/10 This Article is brought to you for free and open access by the Natural Resources, School of at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Papers in Natural Resources by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Ecomorphology of Bats: Comparative and Experimental Approaches Relating Structural Design to Ecology Sharon M. Swartz, Patricia W. Freeman, and Elizabeth F. Stockwell Introduction Interconnections between morphological design and function are central to biology; they underlie natural patterns in species distribution, phylogenetic diversifi cation, and morphological specialization. At its core, ecomorphology explores the causal relationships between organismal design and behavioral performance and investigates how these relationships infl uence an organ- ism’s ability to exploit its environment. To the extent that we can understand mechanisms that dictate these relationships, we can gain broad insight into the ecology and evolution of species, higher-order clades, and ecological assemblages. The past several decades have seen the beginning of integration of discov- eries in the ecology and morphology of bats into an ecomorphological whole that promises to be greater than the sum of its parts. However, achieving this integration is challenging. Each of the elements of this interdisciplinary fi eld is, in itself, avast and complex subject. This book is a testament to the breadth and depth of ecological studies of bats. Morphological studies now extend be- yond descriptive anatomy in both outlook and method, and incorporate, for example, aspects of genetics, physiology, solid and fl uid mechanics, and de- velopmental biology. There is also greater awareness that a particular mor- phology embodies not only the requirements of present life but also an organ- ism’s developmental and evolutionary history. In ecomorphological analysis, one seeks to establish the nature and strength of the relationship between morphology and ecology. The relationship be- tween an animal’s structure and its interactions with its environment may it- self be complicated and multifactorial. Morphology dictates an individual’s performance limits and restricts its behavioral repertoires; regardless of habi- tat, a bat cannot fl y faster or eat larger prey than its anatomy will allow. However, while morphology may constrain potential activities, the ecology of an animal is also strongly infl uenced by the local environment in which it 257 258 S. M. Swartz, P. W. Freeman, and E. F. Stockwell Ecomorphology 259 functions day to day; fl ight speeds employed may be dictated primarily by the form independent of functional analysis. Alternatively, theoretical or mechan- nature of the three-dimensional spatial environment, while prey selection may ical analyses and/or previous experimental studies may suggest that a given be driven by availability and abundance. feature or suite of features are especially important. Part of the intrinsic challenge of the study of ecomorphology is that it is fun- Function or ecology may be quantifi ed as categorizations of aspects of damentally synthetic. This complex subject draws on diverse conceptual ap- habitat, locomotion, food, and so on (e.g., Aldridge 1986b; Aldridge and Raut- proaches, integrates data from the fi eld, the laboratory, and the museum, and enbach 1987; Britton et al. 1997; Saunders and Barclay 1992). Studies of this takes into account both ecological and evolutionary timescales. Moreover, the kind then typically compare morphology and ecology among multiple taxa. volant, nocturnal lifestyles of bats present exceptional methodological chal- Taxonomic sampling can focus specifi cally on phylogenetic lineages (e.g., lenges. Nonetheless, steadily increasing basic knowledge of bat biology along Freeman 1981b; Saunders and Barclay 1992), sympatric communities (e.g., with a growing repertoire of conceptual and methodological approaches have Bonaccorso 1979; Findley 1993), or dietary types (e.g., Fenton 1989, Norberg set the stage for unprecedented innovations in the next few years. and Fenton 1988) or may seek to sample more broadly, even sampling the Here, we examine recent advances in the study of the relationships among total diversity of bats (e.g., Norberg and Rayner 1987). Patterns of interrela- morphology, behavior, and ecology of bats. In this chapter, we provide one tionship among structural and ecological variables can then be described view of ecomorphology as a discipline, and highlight some case studies of par- qualitatively or statistically. ticular relevance to understanding how the morphology of bats relates to their Approaches that reveal patterns of correlation assess general patterns of re- ecology, with special attention to the structure of the feeding apparatus, par- lationship between morphology on the one hand and function or other eco- ticularly the teeth and skull, in relation to dietary preferences, and the mor- logical parameters on the other. Vaughan’s (1959) research on wing anatomy phology of the wing in relation to fl ight performance. In bat ecomorphology, and ecology in three bat species is one classic case in point. Analyses that ex- the feeding and fl ight apparatus have been the subjects of much study; we di- tensively sample morphological and taxonomic diversity may reveal, for ex- rect our focus to these areas, recognizing that other aspects of morphology ample, general associations among wing shape and habitat type (e.g., Findley infl uence behavior and ecology and equally merit further study. et al. 1972; Norberg and Rayner 1987; Smith and Starrett 1979) or among ro- We emphasize several themes; the central role of body size as a determinant bustness of jaws and types of foods eaten (Freeman 1981a, 1981b, 1998). These of mechanical and ecological function; the importance of recognizing ontoge- patterns, in and of themselves, give new insights into the relationship between netic, intersexual, and other intraspecifi c variation; the need for integrative structure and ecology. Additionally, patterns of strong correlation can be used analyses that span fi eld and laboratory; and the role of computer modeling in to predict aspects of the ecology of rare or poorly studied taxa in those in- present and future studies. We offer our views concerning what kinds of in- stances in which their anatomy is well described or is preserved in museum formation are most likely to lead to new insights and effective integration of collections. These taxonomically comprehensive studies are particularly ef- the work of morphologists and ecologists in the future. fective in identifying morphological and ecological extremes, in which rela- tionships among form and ecology may be most readily described and inter- preted. They also characterize subtle variation among more similar species. Correlational Approaches to Assessing Form Correlational approaches can also generate specifi c and testable hypotheses and Its Ecological Signifi cance that explore structural and behavioral relationships more deeply. Results of basic descriptive and correlational analyses are long-lived and can be revisited Background repeatedly as new approaches and data become available. One basic and widely applied approach to ecomorphological analysis assesses aspects of organismal structure as well as its ecological attributes and seeks to Critical Issues in Correlational Analysis describe patterns of interrelationship among them. Comparisons of this kind Body Size Relationships in Ecomorphological Studies may take many forms, depending on the manner in which one characterizes form, function, and/or their interrelationship.. Assessment of morphology can Body size dictates most aspects of organismal ecology and physiology (see range from a simple description of one or a few characters to exhaustive char- Speakman and Thomas, this volume, Willig et al., this volume). It is shaped by acterization of shape. In some cases, investigators evaluate structure with no intra- and interspecifi c interactions and by the physical environment (e.g., preconceived notions about the relative importance of particular features ( e.g., La Barbera 1986; 1989; Peters 1983; Schmidt-Nielsen 1984). In bats, body size Birch 1997; Bookstein 1997; Bookstein et al. 1985; Strauss and Altig 1992). infl uences fl ight behavior, diet selection, roosting, reproductive behavior and These studies seek general descriptors that may capture some critical aspect of physiology, and virtually all other aspects of biology. Understanding patterns 260 S. M. Swartz, P. W. Freeman,