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Christian Peter Klingenberg

Publications and source records attributed to Christian Peter Klingenberg.

12 recordsLinked to original sources
PubMed2006

A single basis for developmental buffering of Drosophila wing shape.

The nature of developmental buffering processes has been debated extensively, based on both theoretical reasoning and empirical studies. In particular, controversy has focused on the question of whether distinct processes are responsible for canalization, the buffering against environmental or genetic variation, and for developmental stability, the buffering against random variation intrinsic in developmental processes. Here, we address this question for the size and shape of Drosophila melanogaster wings in an experimental design with extensively replicated and fully controlled genotypes. The amounts of variation among individuals and of fluctuating asymmetry differ markedly among genotypes, demonstrating a clear genetic basis for size and shape variability. For wing shape, there is a high correlation between the amounts of variation among individuals and fluctuating asymmetry, which indicates a correspondence between the two types of buffering. Likewise, the multivariate patterns of shape variation among individuals and of fluctuating asymmetry show a close association. For wing size, however, the amounts of individual variation and fluctuating asymmetry are not correlated. There was a significant link between the amounts of variation between wing size and shape, more so for fluctuating asymmetry than for variation among individuals. Overall, these experiments indicate a considerable degree of shared control of individual variation and fluctuating asymmetry, although it appears to differ between traits.

Analysis of Variance↗
PubMed2006

Functional evo-devo.

Functional factors such as optimal design and adaptive value have been the central concern of evolutionary biology since the advent of the New Synthesis. By contrast, evolutionary developmental biology (evo-devo) has concentrated primarily on structural factors such as the ways in which body parts can be built. These different emphases have stood in the way of an integrated understanding of the role of development in evolution. Here, we try to bridge this gap by outlining the relevance of functional factors in evo-devo. We use modularity and the view of development as a flexible evolutionary system to outline a unified perspective that includes both structural and functional aspects.

Animals↗
PubMed2005

What accounts for the wide variation in life span of genetically identical organisms reared in a constant environment?

Individual organisms show marked variability in life span, even when they are of the same genotype and are raised in a common environment protected from extrinsic hazards. This intrinsic variability of life span is thought to arise from the stochastic nature of the cellular and molecular mechanisms controlling development and ageing. In this article we review what is currently understood about the factors underlying the variability of life span and consider the implications for research that aims to improve the predictability of health in old age.

Animals↗
PubMed2005

The relationship between fluctuating asymmetry and environmental variance in rhesus macaque skulls.

This study measures the correlation between within- and among-individual variance to gain a greater understanding of the relationship of the underlying mechanisms governing developmental stability and canalization. Twenty-six landmarks were digitized in three dimensions from the crania of 228 adult macaques from Cayo Santiago. The phenotypic variance between individuals was measured and divided into its genetic and environmental components using matriline information. Within-individual variance was measured as the fluctuating asymmetry between bilateral landmarks. We found positive and significant correlations between the phenotypic, environmental, and fluctuating asymmetry variances for interlandmark distances. We also found low but significant correspondences between the covariation structures of the three variability components using both Procrustes and interlandmark distance data. Therefore, we find that in macaque skulls traits that exhibit greater levels of asymmetry deviations also exhibit greater levels of environmental variance, and that the covariances of absolute symmetry deviations partly correspond to covariances of mean deviations at the individual level. These results suggest that the underlying processes that determine canalization and developmental stability are at least partly overlapping. However, the low correlations reported here are also evidence for a degree of independence between these variability components.

Analysis of Variance↗
PubMed2004

Integration and modularity of quantitative trait locus effects on geometric shape in the mouse mandible.

The mouse mandible has long served as a model system for complex morphological structures. Here we use new methodology based on geometric morphometrics to test the hypothesis that the mandible consists of two main modules, the alveolar region and the ascending ramus, and that this modularity is reflected in the effects of quantitative trait loci (QTL). The shape of each mandible was analyzed by the positions of 16 morphological landmarks and these data were analyzed using Procrustes analysis. Interval mapping in the F(2) generation from intercrosses of the LG/J and SM/J strains revealed 33 QTL affecting mandible shape. The QTL effects corresponded to a variety of shape changes, but ordination or a parametric bootstrap test of clustering did not reveal any distinct groups of QTL that would affect primarily one module or the other. The correlations of landmark positions between the two modules tended to be lower than the correlations between arbitrary subsets of landmarks, indicating that the modules were relatively independent of each other and confirming the hypothesized location of the boundary between them. While these results are in agreement with the hypothesis of modularity, they also underscore that modularity is a question of the relative degrees to which QTL contribute to different traits, rather than a question of discrete sets of QTL contributing to discrete sets of traits.

Animals↗
PubMed2002

Morphometrics and the role of the phenotype in studies of the evolution of developmental mechanisms.

Developmental mechanisms are usually assumed to evolve by natural selection of the morphological traits they produce. Therefore, information on phenotypic traits is an important component of comparative studies of development. Morphometrics permits the rigorous quantitative analysis of variation in organismal size and shape, and is increasingly being used in developmental contexts. The new methods of morphometrics combine a geometric concept of shape with the procedures of multivariate statistics, and constitute a powerful and flexible set of tools for analyzing morphological variation. This paper briefly reviews these methods and provides examples of their application in studies of genetic variation and developmental modularity. The results of morphometric analyses can be readily interpreted in relation to the geometry and anatomical structure of the parts under study. Genetic studies of shape in the mouse mandible found two recurrent patterns in environmental and genetic variation from different origins, suggesting that the development system 'channels' the phenotypic expression of variation in similar ways. Moreover, by analyzing the correlations of left-right asymmetries of morphometric traits, it is possible to delimit the spatial extent of developmental modules. These methods complement the experimental approaches of developmental biology and genetics, and can be expected to be especially fruitful in combination with them.

Animals↗
PubMed2002

Shape analysis of symmetric structures: quantifying variation among individuals and asymmetry.

Morphometric studies often consider parts with internal left-right symmetry, for instance, the vertebrate skull. This type of symmetry is called object symmetry and is distinguished from matching symmetry, in which two separate structures exist as mirror images of each other, one on each body side. We explain a method for partitioning the total shape variation of landmark configurations with object symmetry into components of symmetric variation among individuals and asymmetry. This method is based on the Procrustes superimposition of the original and a reflected copy of each landmark configuration and is compatible with the two-factor ANOVA model customary in studies of fluctuating asymmetry. We show a fully multivariate framework for testing the effects in the two-factor model with MANOVA statistics, which also applies to shapes with matching symmetry. We apply the new methods in a small case study of pharyngeal jaws of the Neotropical cichlid fish Amphilophus citrinellus. The analysis revealed that the symmetric component of variation in the pharyngeal jaws is dominated by the contrast between two alternative trophic morphs in this species and that there is subtle but statistically significant directional asymmetry. Finally, we provide some general recommendations for morphometric studies of symmetric shapes.

Analysis of Variance↗
PubMedDate not supplied

Developmental integration in a complex morphological structure: how distinct are the modules in the mouse mandible?

The mouse mandible has long served as a model system for studying the development and evolution of complex morphological structures. We used the methods of geometric morphometrics to reassess the hypothesis that the mandible consists of two separate modules: an anterior part bearing the teeth and a posterior part with muscle attachment surfaces and articulating with the skull. The analyses particularly focused on covariation of fluctuating asymmetry, because such covariation is due exclusively to direct interactions between the developmental processes that produce the traits of interest, whereas variation of traits among individuals also reflects other factors. The patterns of fluctuating asymmetry and individual variation were only partly consistent, indicating that developmental processes contribute differentially to variation at different levels. The results were in agreement with the hypothesis that the anterior and posterior parts of the mandible are separate develop-mental modules. Comparison of all alternative partitions of the landmarks into two contiguous subsets confirmed the hypothesis for the location of the boundary between modules but also underscored that the separation between them is not complete. Modularity is therefore manifest as the relative independence of parts within the framework of overall integration of the mandible as a whole-it is a matter of degrees, not all or nothing.

Analysis of Variance↗