|Shape variation of Drosophila
The fly wing is an ideal model for quantitative morphological studies. Its development is relatively simple, because it is derived from a single sheet of cells folded over once, and it is known in great detail. Moreover, the wing is flat and has many morphological landmarks at the points where the wing veins intersect or meet the wing margin, and is therefore an excellent object for morphometric studies.
Several projects in the lab use the Drosophila wing as a study system. We investigate the genetic basis of wing shape with experimental designs from quantitative genetics and with the use of mutations for specific genes of interest. We particularly focus on fluctuating asymmetry and the factors that influence it.
In addition to the more traditional experimental designs, we are currently initiating broader-scale screens for genes with effects on wing shape and its variability using deficiency stocks. These should enable us to pinpoint genomic regions with substantial effects for further investigation.
We are also working on the evolution of Drosophila wing shape in a phylogenetic perspective, currently with the Drosohila melanogaster subgroup, but we are thinking about doing this on a more extensive scale.
Funding for these projects is provided by BBSRC, NERC, and the European Commission.
Craniofacial shape in mammals
Whereas fly wings are an excellent study system because of their relative simplicity, the skull of mammals is fascinating because of its sheer complexity. The head contains the brain and the main sense organs and also plays a central role for feeding and breathing. To integrate all these different functions, the head goes through an elaborate sequence of embryonic development in which different tissues interact with each other intricately. This interactive development continues after birth through growth and bone remodelling. These processes are of critical importance for evolution as well as the understanding of human health and disease.
Our lab conducts morphometric studies of craniofacial shape variation in different contexts to understand the development and evolution of the skull. The main projects focus on genetics of facial shape in the mouse and on shape variation among dog breeds.
Genetics of mouse craniofacial shape
The skull and mandible of the mouse have been studied in fundamental research and as a model for humans in the context of medical research. The lab is engaged in research on the genetics of mouse craniofacial shape in both these contexts. Morphometric studies on the mouse mandible have been carried out for some time in collaboration with other researchers (e.g. Larry Leamy and Jim Cheverud), and the methodology includes both traditional quantitative genetics and quantitative trait locus (QTL) mapping.
We are currently beginning a new project for mapping QTLs affecting craniofacial shape in mice. This is a collaboration with the group of Jonathan Flint and Richard Mott at the Wellcome Trust Centre for Human Genetics, University of Oxford. The experimental design follows new approach to fine mapping QTLs using a heterogeneous stock of mice (link to reference). Our lab will use geometric morphometrics to quantify craniofacial shape of the mice and analyse the QTL effects. We expect the results will contribute to a better understanding of the genetic basis of craniofacial shape in general and to new insights into the genetic aetiology of craniofacial malformations.
This project is supported by the Wellcome Trust.
Intraspecific macroevolution: variation of cranial shape in dog breeds
The skull shapes of various breeds of domestic dogs, which all belong to a single species, differ by a degree that is normally found at much higher taxonomic levels. Moreover, the ancestor of dogs, the wolf, is still present and can be studied.
The project extends the work begun by Abby Drake in her PhD project (University of Massachusetts) and will focus particularly on the ontogenetic integration among the different parts of the skull.
This project is supported by the Leverhulme Trust.
Development of new morphometric methodology
The members of the lab not only apply the methods of geometric morphometrics in their studies, but we are also engaged in developing new methods. Our particular interest is to use the special structure of biological data to extract information about the underlying biological processes.
Studies of the left-right asymmetry of shape have been an area of particular interest for some time. The goal was to adapt the methods of geometric morphometrics to the statistical designs traditionally used to study asymmetry of linear measurements. Because geometric morphometrics requires a fully multivariate approach, some new aspects such as the comparison of the covariance structure for asymmetry and individual variation have emerged as promising areas for study.
Covariation of left-right asymmetry among traits can be used as a tool to infer the developmental origin of the covariation between traits. We are developing methodology to examine the patterns of developmental integration and modularity.
Another area of interest is the link between morphometrics and phylogeny. We are working on new methods and applications in this area.