The model of development and evolution of complex morphological structures conceived by Atchley and Hall in 1991 (Biol. Rev. 66:101-157), which establishes that changes at the macroscopic, morphogenetic level can be statistically detected as variation in skeletal units at distinct scales, was applied in combination with the formalism of geometric morphometrics to study variation in mandible shape among populations of the rodent species Thrichomys apereoides. The thin-plate spline technique produced geometric descriptors of shape derived from anatomical landmarks in the mandible, which we used with graphical and inferential approaches to partition the contribution of global and localized components to the observed differentiation in mandible shape. A major pattern of morphological differentiation in T. apereoides is attributable to localized components of shape at smaller geometric scales associated with specific morphogenetic units of the mandible. On the other hand, a clinal trend of variation is associated primarily with localized components of shape at larger geometric scales. Morphogenetic mechanisms assumed to be operating to produce the observed differentiation in the specific units of the mandible include mesenchymal condensation differentiation, muscle hypertrophy, and tooth growth. Perspectives for the application of models of morphological evolution and geometric morphometrics to morphologically based systematic biology are considered.493563578Alt, W., Deutsch, A., Dunn, G., (1997) Dynamics of Cell and Tissue Motion, , Springer Verlag, New YorkAtchley, W.R., Genetic and developmental aspects of variability in the mammalian mandible (1993) The Vertebrate Skull, pp. 207-247. , (J. Hanken and B. K. Hall, eds.). Univ. Chicago Press, ChicagoAtchley, W.R., Cowley, D.E., Vogl, C., McLellan, T., Evolutionary divergence, shape change, and genetic correlation structure in the rodent mandible (1992) Syst. Biol., 41, pp. 196-221Atchley, W.R., Hall, B.K., A model for development and evolution of complex morphological structures (1991) Biol. Rev., 66, pp. 101-157Atchley, W.R., Herring, S.W., Riska, B., Plummer, A.A., Effects of the muscular dysgenesis gene on developmental stability in the mouse mandible (1984) J. Craniofacial Genet. Dev. Biol., 4, pp. 179-189Atchley, W.R., Logsdon, T., Cowley, D.E., Eisen, E.J., Uterine effects, epigenetics and post-natal skeletal development in the mouse (1991) Evolution, 45, pp. 891-909Atchley, W.R., Newman, S., Cowley, D.E., Genetic divergence in mandible form in relation to molecular divergence in inbred mouse strains (1988) Genetics, 120, pp. 239-253Bookstein, F.L., Morphometric tools for landmark data (1991) Geometry and Biology, , Cambridge Univ. Press, LondonBookstein, F.L., Biometrics, biomathematics and the morphometric synthesis (1996) Bull. Math. Biol., 58, pp. 313-365Bookstein, F.L., Combining the tools of geometric morphometrics (1996) NATO ASI Ser. A Life Sci., 284, pp. 131-151. , Advances in morphometrics (L. F. Marcus, M. Corti, A. Loy, G. Naylor, and D. E. Slice, eds.)Bookstein, F.L., Standard formula for the uniform shape component in landmark data (1996) NATO ASI Ser. A Life Sci., 284, pp. 153-168. , Advances in morphometrics (L. F. Marcus, M. Corti, A. Loy, G. Naylor, and D. E. Slice, eds.)Brennan, J.M., Fairbairn, D.J., Clinal variation in morphology among eastern populations of the water strider, Aquarius remigis Say (Hemiptera: Gerridae) (1995) Biol. J. Linn. Soc., 54, pp. 151-171Cheverud, J.M., Dow, M.M., Leutenegger, W., The quantitative assessment of phylogenetic constraints in comparative analyses: Sexual dimorphism in body weight among primates (1985) Evolution, 39, pp. 1335-1351Cheverud, J.M., Rouiman, E.J., Irschick, D.J., Pleiotropic effects of individual gene loci on mandibular morphology (1997) Evolution, 51, pp. 2006-2016Christman, M.C., Jernigan, R.W., Spatial correlation models as applied to evolutionary biology (1997) Modelling Longitudinal and Spatially Correlated Data, pp. 221-232. , (T. G. Gregoire, D. R. Brillinger, P. J. Dingle, E. Russek-Cohen, W. G. Warren, and R. D. Wolfinger, eds.). Springer, New YorkChristman, M.C., Jernigan, R.W., Culver, D., A comparison of two models for estimating phylogenetic effect on trait variation (1997) Evolution, 51, pp. 262-266Cushing, J.T., (1998) Phylosophical Concepts in Physics: The Historical Relation between Philosophy and Scientific Theories, , Cambridge Univ. Press, LondonDe Queiroz, K., Good, D.A., Phenetic clustering in biology: A critique (1997) Q. Rev. Biol., 72, pp. 3-30Dryden, I.L., Mardia, K.V., (1998) Statistical Shape Analysis, , John Wiley & Sons, New YorkDuarte, L.C., Boldrini, J.L., Dos Reis, S.F., Scaling phenomena and ecological interactions in space: Cutting to the core (1998) Trends Ecol. Evol., 13, pp. 176-177Edwards, S.V., Kot, M., Comparative methods at the species level: Geographic variation in morphology and group size in grey-crowned babblers (Pomatostomus temporalis) (1995) Evolution, 49, pp. 1134-1146Fitch, W.M., Atchley, W.R., Evolution in inbred strains of mice appears rapid (1985) Science, 228, pp. 1169-1175Fitch, W.M., Atchley, W.R., Divergence in inbred strains of mice: A comparison of three different types of data (1987) Molecules and Morphology in Evolution. Conflict or Compromise?, pp. 203-216. , (C. Patterson, ed.). Cambridge Univ. Press, LondonGabriel, K.R., The biplot graphical display of matrices with application to principal components analysis (1971) Biometrika, 58, pp. 453-467Gandhi, A., Levin, S.A., Orszag, S., Nucleation and relaxation from meta-stability in spatial ecological models (1999) J. Theor. Biol., 200, pp. 121-146Gay, S.W., Best, T.L., Relationship between abiotic variables and geographic variation in skulls of pumas (Puma concolor: Mammalia, Felidae) in North and South America (1996) Zool. J. Linn. Soc., 117, pp. 259-282Gittleman, J.L., Kot, M., Adaptation, statistics, and a null model for estimating phylogenetic effects (1990) Syst. Zool., 39, pp. 227-241Goldman, N., Phylogenetic information and experimental design in molecular systematics (1998) Proc. R. Soc. London. B, 265, pp. 1779-1786Goodall, C.R., Procrustes methods in the statistical analysis of shape (1991) J. R. Stat. Soc. Ser. B, 53, pp. 285-339Hall, B.K., The embryonic development of bone (1988) Am. Sci., 76, pp. 174-181Johnson, D.R., (1986) The Genetics of the Skeleton, , Clarendon Press, OxfordKendall, D.G., Shape-manifolds, procrustean metrics, and complex projective spaces (1984) Bull. London Math. Soc., 16, pp. 81-121Kendall, D.G., A survey of the statistical theory of shape (1989) Stat. Sci., 4, pp. 87-120Krzanowski, W.J., (1989) Principles of Multivariate Analysis: A User's Perspective, , Clarendon Press, Oxford, EnglandKrzanowski, W.J., Radley, D., Nonparametric confidence and tolerance regions in canonical variate analysis (1989) Biometrics, 45, pp. 1163-1173Levin, S.A., The problem of scale in ecology (1992) Ecology, 73, pp. 1943-1967Levin, S.A., Pacala, S.W., Theories of simplification and scaling of spatially distributed processes (1997) Space Ecology: The Role of Space in Population Dynamics and Interspecific Interactions, pp. 271-295. , (D. Tilman, and P. Kareiva, eds.). Princeton Univ. Press, Princeton, New JerseyLongair, M.S., (1994) Theoretical Concepts in Physics, , Cambridge Univ. Press, LondonMardia, K.V., Kent, J.T., Bibby, J.M., (1978) Multivariate Analysis, , Academic Press, LondonMares, M.A., Willig, M.R., Lacher, T.E., The Brazilian caatinga in South American zoogeography: Tropical mammals in dry regions (1985) J. Biogeogr., 12, pp. 57-69Meacham, C.A., Duncan, T., (1993) MorphoSys: Automated Morphometric System, , Univ. California, BerkeleyMoojen, J., (1952) Roedores do Brasil, , Instituto Nacional do Livro, Rio de JaneiroMoojen, J., Dos Reis, S.F., Dellape, M.V., Quantitative variation in Thrichomys apereoides (Lund, 1841) (Rodentia: Echimyidae). I. Non-geographic variation (1988) Bol. Mus. Nac. (Rio de Janeiro), 316, pp. 1-15Monteiro, L.R., Multivariate regression models and geometric morphometrics: The search for causal factors in the analysis of shape (1999) Syst. Biol., 48, pp. 192-199Monteiro, L.R., Abe, A.S., Functional and historical determinants of shape in the scapula of xenarthran mammals: Evolution of a complex morphological structure (1999) J. Morphol., 241, pp. 251-263Monteiro, L.R., Lessa, L.G., Abe, A.S., Ontogenetic variation in skull shape of Thrichomys apereoides (Echimyidae: Rodentia) (1999) J. Mammal., 80, pp. 102-111Newton, R.G., (1997) The Truth of Science: Physical Theories and Reality, , Harvard Univ. Press, Cambridge, MassachusettsPascual, M., Levin, S.A., From individuals to population densities: Searching for the intermediate scale of nontrivial determinism (1999) Ecology, 80, pp. 2225-2236Patton, J.L., Smith, M.F., Evolutionary dynamics of Thomomys bottae pocket gophers, with special emphasis on California populations (1990) Univ. Calif. Publ. Zool., 123, pp. 1-161Patton, J.L., Smith, M.F., Paraphyly, polyphyly, and the nature of species boundaries in pocket gophers (genus Thomomys) (1994) Syst. Biol., 43, pp. 11-26Perelson, A.S., Weisbuch, G., Immunology for physicists (1997) Rev. Mod. Phys., 69, pp. 1219-1268Ringrose, T.J., Alternative confidence regions for canonical variate analysis (1996) Biometrika, 83, pp. 575-587Rohlf, F.J., Morphometric spaces, shape components, and the effects of linear transformations (1996) NATO ASI Ser. A Life Sci., 284, pp. 117-129. , Advances in morphometrics (L. F. Marcus, M. Corti, A. Loy, G. Naylor, and D. E. Slice, eds.)Rohlf, F.J., (1997) TPSREGR, Version 1.08. A Program to Perform Multivariate Regression of Partial Warps on Independent Variables, , Department of Ecology and Evolution, State Univ. New York at Stony BrookRohlf, F.J., On applications of geometric morphometrics to studies of ontogeny and phylogeny (1998) Syst. Biol., 47, pp. 147-158Rohlf, F.J., Loy, A., Corti, M., Morphometric analysis of old world Talpidae (Mammalia, Insectivora) using partial-warp scores (1996) Syst. Biol., 45, pp. 344-362Rohlf, F.J., Marcus, L.F., A revolution in morphometrics (1993) Trends Ecol. Evol., 8, pp. 129-132Rohlf, F.J., Slice, D., Extensions of the procrustes method for the optimal superimposition of landmarks (1990) Syst. Zool., 39, pp. 40-59Sharples, C.M., Fa, J.E., Bell, D.J., Geographical variation in size in the European rabbit Oryctolagus cuniculus (Lagomorpha: Leporidae) in western Europe and North Africa (1996) Zool. J. Linn. Soc., 117, pp. 141-158Small, C.G., (1996) The Statistical Theory of Shape, , Springer, New YorkSmith, H.M., Chiszar, D., Montanucci, R.R., Subspecies and classification (1997) Herpetol. Rev., 28, pp. 13-16Smith, M.F., Patton, J.L., Subspecies of pocket gophers: Causal bases for geographic differentiation in Thomomys bottae (1988) Syst. Zool., 37, pp. 163-178Straney, D.O., Patton, J.L., Phylogenetic and environmental determinants of geographic variation in the pocket mouse Perognathus goldmani Osgood (1980) Evolution, 34, pp. 888-903Strang, G., (1988) Linear Algebra and Its Applications, 3rd Edition, , Harcourt Brace Jovanovich, San DiegoThorpe, R.S., Geographic variation: A synthesis of cause, data, pattern and congruence in relation to subspecies, multivariate analysis and phylogenesis (1987) Boll. Zool., 54, pp. 3-11Von Zuben, F.J., Duarte, L.C., Stangenhaus, G., Pessoa, L.M., Dos Reis, S.F., Bootstrap confidence regions for canonical variates: Application to studies of evolutionary differentiation (1998) Biom. J., 40, pp. 327-339Weber, K.E., How small are the smallest selectable domains of form? (1992) Genetics, 130, pp. 345-353Woods, C.A., Suborder hystricognathi (1993) Mammal Species of the World: A Taxonomic and Geographic Reference 2nd Edition, pp. 771-806. , (D. E. Wilson and D. M. Reeder, eds.). Smithsonian Institute Press, Washington, D.CWright, S., Isolation by distance (1943) Genetics, 28, pp. 114-138