Pleiotropic effects on mandibular morphology II: Differential epistasis and genetic variation in morphological integration

Cheverud, James M.; Ehrich, Thomas H.; Vaughn, Ty T.; Koreishi, Safina F.; Linsey, Robin B.; Pletscher, L. Susan

doi:10.1002/jez.b.21008

Cited by 100 publications

(62 citation statements)

References 42 publications

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“…In essence, a few QTLs with statistically significant effects are identified, and used to check whether hypothesized integrated traits share QTLs. Of particular interest for the evolution of pleiotropy and integration are studies of differential epistasis [83,84,103,183]. These studies identify relationship QTLs that modify the pleiotropic effects of other QTLs, and thus give evidence for genetic variation in trait covariance.…”

Section: Measurement Of Integration and Modularitymentioning

confidence: 99%

Integrated phenotypes: understanding trait covariation in plants and animals

Armbruster

Pélabon

Bolstad

et al. 2014

Phil. Trans. R. Soc. B

245

232

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Integration and modularity refer to the patterns and processes of trait interaction and independence. Both terms have complex histories with respect to both conceptualization and quantification, resulting in a plethora of integration indices in use. We review briefly the divergent definitions, uses and measures of integration and modularity and make conceptual links to allometry. We also discuss how integration and modularity might evolve. Although integration is generally thought to be generated and maintained by correlational selection, theoretical considerations suggest the relationship is not straightforward. We caution here against uncontrolled comparisons of indices across studies. In the absence of controls for trait number, dimensionality, homology, development and function, it is difficult, or even impossible, to compare integration indices across organisms or traits. We suggest that care be invested in relating measurement to underlying theory or hypotheses, and that summative, theory-free descriptors of integration generally be avoided. The papers that follow in this Theme Issue illustrate the diversity of approaches to studying integration and modularity, highlighting strengths and pitfalls that await researchers investigating integration in plants and animals.

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Section: Measurement Of Integration and Modularitymentioning

confidence: 99%

Integrated phenotypes: understanding trait covariation in plants and animals

Armbruster

Pélabon

Bolstad

et al. 2014

Phil. Trans. R. Soc. B

245

232

View full text Add to dashboard Cite

show abstract

“…Usually, the emphasis in the quantitative genetics literature is placed on correlation between traits being produced by pleiotropy , because linkage disequilibrium is usually thought to be transient (unless actively maintained by selection) due to recombination among loci. Recent studies of genetic architecture in many organisms, and especially in mammals, have found ample evidence of a modular organization with pleiotropic effects usually falling within phenotypic modules and being reduced among modules (Ehrich et al 2003;Cheverud et al 2004;Wagner et al 2008;Kenney-Hunt et al 2008). Accordingly, a prerequisite for the evolution of modularity is that pleiotropy must be genetically variable.…”

Section: Introductionmentioning

confidence: 98%

The Evolution of Modularity in the Mammalian Skull I: Morphological Integration Patterns and Magnitudes

et al. 2008

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Morphological integration refers to the modular structuring of inter-trait relationships in an organism, which could bias the direction and rate of morphological change, either constraining or facilitating evolution along certain dimensions of the morphospace. Therefore, the description of patterns and magnitudes of morphological integration and the analysis of their evolutionary consequences are central to understand the evolution of complex traits. Here we analyze morphological integration in the skull of several mammalian orders, addressing the following questions: are there common patterns of inter-trait relationships? Are these patterns compatible with hypotheses based on shared development and function? Do morphological integration patterns and magnitudes vary in the same way across groups? We digitized more than 3,500 specimens spanning 15 mammalian orders, estimated the correspondent pooled within-group correlation and variance/covariance matrices for 35 skull traits and compared those matrices among the orders. We also compared observed patterns of integration to theoretical expectations based on common development and function. Our results point to a largely shared pattern of inter-trait correlations, implying that mammalian skull diversity has been produced upon a common covariance structure that remained similar for at least 65 million years. Comparisons with a rodent genetic variance/covariance matrix suggest that this broad similarity extends also to the genetic factors underlying phenotypic variation. In contrast to the relative constancy of inter-trait correlation/covariance patterns, magnitudes varied markedly across groups. Several morphological modules hypothesized from shared development and function were detected in the mammalian taxa studied. Our data provide evidence that mammalian skull evolution can be viewed as a history of inter-module parcellation, with the modules themselves being more clearly marked in those lineages with lower overall magnitude of integration. The implication of these findings is that the main evolutionary trend in the mammalian skull was one of decreasing the constraints to evolution by promoting a more modular architecture.

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“…Finally, there is discussion about whether the relationship between traits represents yet another phenotype that can be affected by genetic manipulation. Relationship QTL, or rQTL, which change the relationships between phenotypes have been identified in mice, 4,5 and are likely present in other organisms as well.…”

Section: Introductionmentioning

confidence: 99%