Current Research Interests:

           My most recent work has focused on the aggregation of variables representations of the mutation-selection process. The basic idea behind the approach is that for certain choices of fitness functions and mutation rates, there exist sets of genotypes that behave as self-contained "modules" that act as "emergent" higher-order entities in their interactions with other such modules in the genotype space. It is hoped that this methodology will not only be of value from the standpoint of computational efficiency, but will also shed light on conceptual issues related to the units of selection question.
         The eventual goal is to incorporate recombination-selection dynamics into this framework, which is a substantially more difficult task because the formalism I am working with is specific to linear dynamical systems. Therefore, including recombination in this context requires either a linearization of the recombination operator, or else a generalization of the aggregation model to quadratic systems. If successful, an aggregation of variables representation of the recombination process may find a number of biological applications, such as furthering our understanding of the process of speciation.
         In addition, I am engaged in a study of semelparous vs. iteroparous reproductive strategies (from a "bet-hedging" perspective) in the context of metapopulation dynamics. I am also collaborating on a more empirically-oriented project investigating the saturation of morphospace during the adaptive radiation of gammarid amphipods in Lake Baikal using both phylogenetic and morphometric methods.

References on Aggregation of Variables:

Shpak, M., P.F. Stadler, G.P. Wagner, and J. Hermisson, 2004. Aggregation of variables and system decomposition: application to fitness landscape analysis. Theory in Biosciences 123: 33-68. Earlier Draft at the SFI Preprint Server

Shpak, M., P.F. Stadler, G.P. Wagner, and L. Altenberg, 2004. Simon-Ando decomposability and mutation-selection dynamics. Theory in Biosciences 123: 139-180. Preprint at Peter Stadler's Webpage

       
      Miscellaneous Research Interests:

           My past research projects have included work on the properties of non-Mendelian recombination models (particularly unequal crossover), individual-based and analytical models of speciation and hybrid zone structure, and the application of information-theoretic approaches to phylogenetic analysis. I also maintain an interest in the systematics and natural history of lower vertebrates, and am a Curatorial Affiliate at the Yale Peabody Museum of Natural History.

Publications: