Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Review
. 2019 Nov 1;59(5):1369-1381.
doi: 10.1093/icb/icz105.

Integration and the Developmental Genetics of Allometry

Affiliations
Review

Integration and the Developmental Genetics of Allometry

Benedikt Hallgrímsson et al. Integr Comp Biol. .

Abstract

Allometry refers to the ways in which organismal shape is associated with size. It is a special case of integration, or the tendency for traits to covary, in that variation in size is ubiquitous and evolutionarily important. Allometric variation is so commonly observed that it is routinely removed from morphometric analyses or invoked as an explanation for evolutionary change. In this case, familiarity is mistaken for understanding because rarely do we know the mechanisms by which shape correlates with size or understand their significance. As with other forms of integration, allometric variation is generated by variation in developmental processes that affect multiple traits, resulting in patterns of covariation. Given this perspective, we can dissect the genetic and developmental determinants of allometric variation. Our work on the developmental and genetic basis for allometric variation in craniofacial shape in mice and humans has revealed that allometric variation is highly polygenic. Different measures of size are associated with distinct but overlapping patterns of allometric variation. These patterns converge in part on a common genetic basis. Finally, environmental modulation of size often generates variation along allometric trajectories, but the timing of genetic and environmental perturbations can produce deviations from allometric patterns when traits are differentially sensitive over developmental time. These results question the validity of viewing allometry as a singular phenomenon distinct from morphological integration more generally.

PubMed Disclaimer

Figures

Fig. 1
Fig. 1
The palimpsest model for the generation of covariation structure. The tissue-level processes listed are not exhaustive and intended only to illustrate the concept. Processes acting at different times and scales of development drive covariation among traits that may be transient or persist to influence the adult covariation structure.
Fig. 2
Fig. 2
The covariation of facial shape with different measures of size in children. (A) shows the covariation of human facial shape with different measures of size. (B) shows the directions of change associated with each of the regressions of facial shape on a measure of size. Panel A is taken from Fig. 6 in Larson et al. (2018) and panel B is Fig. 8A in the same paper.
Fig. 3
Fig. 3
The genetic basis for “allometric” variation as quantified using cranial centroid size and body mass. (A) shows the shape vectors associated with the regressions of craniofacial shape on cranial CS and BM. (B) shows absolute loadings for variation at SNP and allometric variation as quantified using CS and BM. (C) shows the distribution of SNPs with effects on allometric variation as quantified using CS, BM or both. This shows that a large proportion of SNPs affect only or the other form of allometric variation. (D) shows the proportion of variance explained by MGP analyses of SNPs annotated to be associated with the BMP pathway, cell division, chondrocyte proliferation and growth. (E) shows QTL scan results for allometric variation as determined by regressions of facial shape on cranial centroid size and body mass.
Fig. 4
Fig. 4
Growth faltering and facial shape in Tanzanian children. (A) plots growth outcomes by school for the entire sample. Growth faltering is the first PC of all growth attainment variables relative to age. (B) visualizes the correlation matrix for the first 10 PCs of the genetic and environmental variance covariance matrices. (C) shows the variation in facial shape associated with growth faltering. (D) plots school average values for growth attainment and environmental PCs 1 and 3. (E) shows the facial shape variation associated with environmental PCs 1 and 3 as morphs and heatmaps. (F) summarizes the relationship between growth faltering and the partial regressions of facial shape on height and age. These figures are taken from Figs 3, 7 and 8 in Cole et al. (2018).
Fig. 5
Fig. 5
Rescue of growth by growth hormone in growth hormone deficient mice. (A) shows mean craniofacial shapes at 60 days for all treatment groups. (B) shows the growth trajectories for the whole skull, the basicranium, face and cranial vault. (C) shows average brain size by treatment groups. The error bars are standard errors of the mean. (D) shows the result of a between group PCA for all treatment groups. The best fit lines show ontogenetic progression with age within each group. (E) shows the analysis of longitudinal shape change from one age group to the next for the face only. All panels are taken from Gonzalez et al. (2013).

References

    1. Adams DC, Collyer ML, Otarola-Castillo E, Sherratt E.. 2014. geomorph: Software for geometric morphometric analyses. R package version 2.1. http://cran.r-project.org/web/ packages/geomorph/index.html.
    1. Baker J, Workman M, Bedrick E, Frey MA, Hurtado M, Pearson O.. 2010. Brains versus brawn: an empirical test of Barker's brain sparing model. Am J Hum Biol 22:206–15. - PubMed
    1. Broman KW, Gatti DM, Simecek P, Furlotte NA, Prins P, Sen Ś, Yandell BS, Churchill GA. 2019. R/qtl2: Software for Mapping Quantitative Trait Loci with High-Dimensional Data and Multiparent Populations. Genetics 211:495. - PMC - PubMed
    1. Cahill LS, Zhou YQ, Seed M, Macgowan CK, Sled JG.. 2014. Brain sparing in fetal mice: BOLD MRI and Doppler ultrasound show blood redistribution during hypoxia. J Cereb Blood Flow Metab 34:1082–8. - PMC - PubMed
    1. Calder WA. 1996. Size, function, and life history. Cambridge (MA): Harvard University Press.

Publication types