Individual Variation in Mammals

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. American Society of Mammalogists is collaborating with JSTOR to digitize, preserve and extend access to Journal of Mammalogy.The study of individual variation offers an underexploited wealth of opportunities for mammalogists. This paper addresses recent developments in the study of both intra-and interindividual variation. After reviewing several methods (e.g., intraclass correlation, productmoment correlation, and confirmatory factor analysis) for quantifying intra-individual consistency or repeatability, we discuss how these measures of repeatability can serve as guides for appropriately defining traits and how they may be helpful in ensuring that appropriate statistical models are used (e.g., in accounting for measurement errors in regression analyses). We discuss three aspects of inter-individual variation; phenotypic selection, alternative individual strategies and phenotypic integration, and quantitative genetic analyses. The value of these approaches for studying inter-individual variation is illustrated with recent examples from the literature. Finally, we discuss how many field studies of mammals may be well poised to exploit the unique insights that can be gained from studying individual variation. Speakman et al., 1994). The study of individual variation has an illustrious history, forming one of the cornerstones of Darwin's theory of evolution by natural selection (Darwin, 1958). While much has been written about individual variation since Darwin's time (Schmalhausen, 1949; Yablokov, 1974), many biological insights remain to be gained by studying it. Indeed, stimulated by physiologists (Bennett, 1987), population biologists (Clutton-Brock, 1988), and behaviorists (Boake, 1989), the study of individual variation is undergoing a renaissance, to which mammalogists are paying increasing attention (BlankIndividual variation can be defined in many ways but, most broadly defined, it is synonymous with intraspecific variation. Accordingly, individual variation would include differences related to group attributes (e.g., all members of a rodent population oc-cupying habitat with dark volcanic soils might have dark pelage, while their conspecifics occupying pale-colored sands might all have pale pelage-Benson, 1933). In this example, as in many comparisons among populations (Garland and Adolph, 1991), the variation (i.e., in pelage color) is more usefully attributed to variation among groups than to variation among individuals. Among-group variation is important, but we believe it is fruitfully considered separately from variation within populations. Consequently, for this paper, we define individual variation as differences among individuals within a population, following Darw...

Behavioural and kinematic components of the fast-start escape response in fish: individual variation and temporal repeatability

“…To have such significance, it is essential to demonstrate that individual variation in the trait is temporally stable and therefore an intrinsic, potentially life-long, characteristic of the individual (Oufiero and Garland, 2009), and thus subject to natural selection (Arnold, 1983). The existence of standing variation is essential for the trait to evolve in response to future environmental change (Hayes and Jenkins, 1997;Bolnick et al, 2003;Sears et al, 2009), and it may be indicative of underlying physiological or behavioural tradeoffs within or amongst traits such that no single phenotype is best under all circumstances (Mangel and Stamps, 2001;Stamps, 2007).…”

Individual variation and repeatability of basal metabolism in the bank vole,Clethrionomys glareolus

“…As the paradigm of evolutionary physiology has developed (Bennett 1987;Garland & Carter 1994;Feder et al 2000), the research on ecological and evolutionary aspects of BMR has become more focused on variation across individuals (Hayes 1989;Hayes et al 1992a;Konarzewski & Diamond 1995;Koteja 1996a;Speakman & McQueenie 1996;Hayes & Jenkins 1997;Meerlo et al 1997;Chappell et al 1999;Dohm et al 2001;Nespolo et al 2003a,b). Natural selection does work primarily at the level of variation across individuals.…”

Body temperatures of house mice artificially selected for high voluntary wheel-running behavior: repeatability and effect of genetic selection

“…We know, for example, that body temperature follows a circadian rhythm (Re®netti, 1994;Re®netti and Menaker, 1992) and that locomotor activity and body temperature are positively correlated (Bolles et al, 1968;Gordon and Yang, 1997;Honma and Hiroshige, 1978;Re®netti, 1994). Few studies, however, have focused on body temperature di erences among individual animals (Hayes and Jenkins, 1997) or among populations within a single species (Garland and Adolph, 1991). Connolly and Lynch (1981) measured body tempera-ture around the clock in four di erent inbred strains of mice to estimate broad-sense heritability (ratio of total genetic variance to phenotypic variance).…”