A central goal of evolutionary biology is to understand the relative importance of internal proximate (genetic, physiological, developmental) mechanisms and external selective forces in the evolution of complex, multivariate phenotypes. In field and laboratory studies, I will continue to use naturally occurring and experimentally produced extreme phenotypic variants to elucidate the relationships among variation in genotype, physiology, ecological performance, and fitness. My goal is to understand how both proximate mechanisms and external selection influence the evolution of complex phenotypes that are composed of functionally and developmentally integrated trait suites. My research is often collaborative and necessarily integrative, combining behavioral, comparative, developmental genetic, genomic, quantitative genetic, phenotypic engineering, and other experimental approaches.

I am building my research program around investigating the evolution of complex morphological phenotypes using insect wing shape, absolute wing size, and the allometric relationships between the wings and other traits as focal systems. Wings are well suited for the study of complex phenotype evolution because they are ecologically important, amenable to experimental manipulation, genetically and developmentally tractable, and because wing size and wing shape are easily quantified. I will continue working on Bicyclus and will use additional biological systems to answer specific questions. Currently, I use Drosophila to study the genetic basis of wing size and wing shape evolution.

My approach has four broad components: (1) the identification of pattern in morphological evolution through comparative analysis of multivariate descriptors, (2) the experimental creation of new morphological variation through artificial selection or phenotypic engineering to test for internal constraints and bias in phenotype evolution, (3) investigation of the proximate (genetic, physiological) basis of typical and novel phenotype development, and (4) the use of experimentally produced novel phenotypic variation to describe the relationships between variation in morphology, ecological performance, and fitness. This research program, outlined below, aims to elucidate the relationships among the proximate and ecological factors that connect genotypic variation to fitness variation. Ultimately, my goal is to explain patterns of morphological diversity through the relative contributions of internal factors and external selection.

1. Comparative Work
Lepidoptera and Diptera both exhibit substantial variation in wing shape and relative wing size. Using comparative morphometric methods, I will quantify pattern in wing shape evolution among groups (e.g. genera, species, populations, morphs) with the goals of (i) identifying unlikely (‘forbidden’) wing morphologies, (ii) determining if there are regions within the wing that are biased towards change or stasis, and (iii) relating this to what is known regarding the proximate basis of wing size and shape determination. For example, preliminary work on my artificially selected B. anynana lineages shows dramatic shape change in the distal portion of the forewing, supporting the view that Distal-less expression in this region creates a putative developmental module with high evolvability. Interestingly, this wing region corresponds to a primary area of shape change I have identified among Drosophila species.

2 &3. Artificial Selection and the Proximate Basis of Trait Variation
I will use artificial selection or engineering approaches on Bicyclus, Drosophila, and possibly other Lepidoptera and Diptera, to create novel phenotypes and to test hypotheses regarding the existence of ‘forbidden’ morphologies (e.g., Frankino et al. 2005) identified through the comparative work in (1). In particular, I am interested in using multivariate selection approaches to generate novel, extreme wing shapes or allometries among morphological traits. Lineages with new phenotypes can then be used to investigate the proximate bases of trait integration, of the response to selection, and to dissect the external selective forces acting on these phenotypes as described below in (4).

I will investigate the proximate basis of the response to artificial selection using the integrative approaches outlined above. In particular, Drosophila will be used to dissect the genetic basis of the response to artificial selection, whereas the large size of Lepidopterans make them amenable to investigations of the physiological basis of the response to selection. Longer-term goals of this work include comparing the proximate basis of trait divergence between artificially selected and naturally divergent lineages; such work will determine if the mechanisms underling trait evolution in artificial settings differ from those responsible for divergence over different time scales in large populations.

This work will also be used to develop 'phenotype maps' for wing shape to enable evaluation of quantitative genetic models (e.g., Wolf et al. 2001; Wolf et al. 2004; Frankino and Agrawal in prep) that explicitly consider the nature of developmental integration (e.g., additive versus non-additive epistasis) among traits when predicting the evolutionary trajectories of complex phenotypes. Such tests are critical for the advancement of a predictive, generalized evo-devo theory.

4. Natural Selection and Ecological Performance.
The increased range of phenotypic variation and atypical patterns of trait covariation produced in (2) will be used to (i) establish the relationship between trait variation and performance variation and (ii) to quantify the shape and strength of natural selection acting on individual components within suites of typically correlated traits. In both flies and butterflies, I will undertake functional morphology work to isolate the contribution of individual traits to variation in locomotor performance. I will also perform mark-recapture studies of butterflies with experimentally altered phenotypes to quantify selection on focal traits in nature.


Building the Research Group.
I look forward to building a research group that uses this integrative approach to study the evolution of complex phenotypes. My membership in the international, collaborative effort to develop Bicyclus as a model system will facilitate (and partially fund) movement of researchers at all levels of experience between my lab and the others in the network. Such an inside track on known talent will allow me to quickly build, and later enhance, my own group through recruitment and researcher 'exchanges'. I believe my diverse research experience to be a strong asset when advising on a broad range of topics and systems. Consequently, although my research focus will be on insect systems (and on insect wings in particular), members of my group will be able to work on any feasible biological system appropriate to their topic of interest. As a first start, our grant recently funded by Netherlands Organization for Scientific Research (NWO, the Dutch equivalent of NSF), will support such researcher exchanges and some of the current and future Bicyclus work here.

Suggested research programs are described in these reviews:

Frankino, W. A., and R. A. Raff. 2004. Evolutionary importance and pattern of phenotypic plasticity: Insights gained from development. Pp. 64-81 in T. J. DeWitt and S. M. Scheiner, eds. Phenotypic Plasticity, Functional and Conceptual Approaches. Oxford Press.

Brakefield, P. M., and W. A. Frankino. 2006. Polyphenisms in Lepidoptera: Multidisciplinary approaches to studies of evolution. in T. N. Ananthakrishnan and D. W. Whitman, eds. Phenotypic Plasticity in Insects. Oxford University Press, Oxford. in press.

Shingleton, A., W. A. Frankino, T. Flatt, F. Nijhout, and D. Emlen. Developmental mechanisms and the evolution of allometries. ms in prep.