Variation in Mandible Shape in Thrichomys apereoides (Mammalia: Rodentia): Geometric Analysis of a Complex Morphological Structure

Authors: Duarte L.C.¹; Monteiro L.R.²; Zuben F.J.³; Reis S.F.D.⁴

Source: Systematic Biology, Volume 49, Number 3, 1 July 2000 , pp. 563-578(16)

Publisher: Taylor and Francis Ltd

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Abstract:

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.

Keywords: COMPLEX MORPHOLOGICAL STRUCTURES; GEOMETRIC MORPHOMETRICS; MORPHOLOGICAL EVOLUTION; THIN-PLATE SPLINES; THRICHOMYS; APEREOIDES

Language: English

Document Type: Research article

Affiliations: 1: Programa de Pós-Graduação em Zoologia, Universidade Estadual Paulista, Caixa Postal 179, 13506-900 Rio Claro, São Paulo, Brazil 2: Laboratório de Ciências Ambientais—CBB, Universidade Estadual do Norte Fluminense, Av. Alberto Lamego 2000, Horto, 28015–620 Campos dos Goytacazes, Rio de Janeiro, Brazil 3: de Engenharia de Computação e Automação Industrial, Faculdade de Engenharia Ele´trica e Computação, Universidade Estadual de Campinas, 13083-970 Campinas, São Paulo, Brazil 4: Departamento de Parasitologia, Instituto de Biologia, Universidade Estadual de Campinas, 13083-970 Campinas, São Paulo, Brazil

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