NSF Postdoctoral Fellowship in Biology FY 2012

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Function and rates of diversification in complex miniature structures: the trap-jaw mechanisms in spiders The goal of this research is to use principles of engineering to discover basic mechanical patterns in the function of a complex biological structure, and then to use these findings to examine evolutionary diversification. Studies that determine function are essential for understanding how species diversify. However, such studies are difficult on the millimeter-sized organisms that tend to make up the majority of earth?s diversity, as size limitations make dissections and in vivo manipulations virtually impossible. However, synchrotron-based micro-tomography scanning presents a means for gathering detailed information about internal minute biological structures in even the smallest organisms. This technique is crucial in the case of the millimeter-sized trap-jaw spider family. Within this family extremely rapid, inertia-based, jaw closing mechanisms have evolved 3-4 times independently. Synchrotron scans will allow for visualizing internal musculature and structures implicated in jaw function, but also, this technique will allow for constructing 3D computer models to be used as inputs for kinematic simulations. Results from these simulations, coupled with a pre-existing phylogeny, will allow for testing (1) the hypothesis that changes in form directly relate to changes in function; and (2) the hypothesis that patterns of species diversification are proportional to rates of morphological and functional change.Training includes learning techniques for reconstructing 3D computer models from synchrotron-based tomography scans, performing kinematic simulations, and running statistical analyses that determine shifts among lineages in rates of evolutionary diversification and functional and morphological change. Broader impacts during the course of the postdoctoral fellowship include training and mentoring undergraduates, giving guest lectures in undergraduate courses, and making results, such as 3D digital reconstructions, available online. Other opportunities for community outreach include presenting research at public venues and creating online lesson plans that facilitate the teaching of evolution.