T
he animal kingdom contains staggering morphological diversity, but even greater variety is manifest in animal behavior. All animals display species-specific ecological behaviors (such as preferentially interacting with members of the same species), and behavior alone can distinguish species that are otherwise morphologically identical - e.g. two cricket species in the genus Gryllus that inhabit the same range and ecological niche but are distinguished only by distinct mating songs.

Moreover, evolution and behavior exert reciprocal influences on each other - while evolution can diversify behavior, behavior can constrain the evolution of species. For example, in sympatric speciation, behavior provides the reproductive barrier between sub-populations whose hybrid offspring have reduced fitness. In another classic example, two species of periodic cicada with overlapping range emerge to mate after different prime-numbered year intervals, a behavioral strategy that reduces the evolutionary pressures associated with multiple swarms emerging in the same year and periodically abundant predators.

The goal of our lab is to understand the neurobiological mechanisms of ecologically and evolutionarily relevant behaviors using techniques drawn from circuit-driven neuroscience, comparative genomics, and ethology, as they are manifested in fruit flies from the genus Drosophila.

We have previously worked on projects in several other fields of biology, including: cell biology, microbiology, metabolism, systems biology, and arthropod systematics.

W
hat genetic changes underly the evolved differences in behavior between related strains and species? A number of classic fly behavior papers (Dobzhansky et al., 1974; Levene et al., 1976) showed that natural populations of Drosophila pseudoobscura could be artificially selected for positive and negative phototaxis over a small number of generations.

This genetic plasticity likely has mediated the strain and species-level differences in phototaxis we have observed using a number of assays. We are currently using quantitative trait localization to identify the genetic loci responsible for the behavioral differences between several pairs of Drosophila species and strains.

W
hat underlies the behavioral differences between genetically identical individuals? One can consider behavioral diversity at a number of scales. Arthropods may on average behave differently than vertebrates - sister species differ behaviorally either by drift or selection for mating isolation - the behavior of strains within a species may vary due to differential allelic frequencies or phenotypic plasticity - and genetically identical siblings display non-heritable behavioral differences. In humans, this is called personality.

We have found that even in isogenized stocks of fruit flies, individuals display idiosyncratic behaviors in a number of paradigms. In all strains tested, whether they prefer on average to run toward light or darkness when startled, some individuals are more photo-positive or photo-negative than their clonal siblings. While not showing a species-level bias, individual flies prefer to choose either left or right turns in branching mazes. These idiosyncrasies are not heritable, but last the lifetime of the flies, and therefore constitute a form of personality.

I
s there a basic behavioral vocabulary? The modularity of developmental signaling pathways appears to be essential for the generation of diverse animals forms through evolution by natural selection. Rather than evolve new genes and signaling pathways to generate a wing or antenna from scratch, it is sufficient to reuse the modular signaling pathways that generate limbs, particularly since each insulated pathway typically controls an independent physical parameter of development, such as limb length, width, or number of segments. Could behavioral modularity be analogously utilized in the generation of behavioral diversity?

We are addressing this question using dimension-reducing analytic methods on high-resolution temporal and spatial data of single flies performing spontaneous walking behavior on floating balls.