Dissertation Research: Linking Development with Evolution: morphological and ecological consequences associated with limb regeneration in walking sticks. Dr. Douglas Emlen Tara Prestholdt University of Montana
Walking Sticks (Order: Phasmida) are unique among insects in that they regularly shed and regenerate lost legs. However, this developmental capacity comes at a price: resources used to re-grow a leg come at the expense of other structures. Depending on the species, walking sticks regenerating a leg may experience decreased wing area (as in Sipyloidea sipylus - the pink winged walking stick), decreased fecundity (as in Carasious morosus, the common walking stick), and/or decreased weapon size (as in Eurycantha calcarata - the Giant spiny stick insect that has enlarged hind legs used in male-male competitions). Developmental tradeoffs associated with leg regeneration may have important performance and fitness consequences for these animals in the wild (e.g. impaired flight ability or decreased fighting ability). However, these animals remain almost entirely unexplored in their natural habitats, and it is not yet known how often these animals shed and regenerate limbs in their natural environment. This project entails a rigorous study of the causes and consequences of walking stick leg-regeneration in the wild. By (1) demonstrating how often leg-regeneration occurs, (2) what the consequences of regeneration are, and (3) placing this information within an explicit ecological context, we will increase our understanding of how developmental processes (such as regeneration) impact evolution. The concept of tradeoffs can be generalized, and the idea that regeneration has measurable costs - and that these costs differ in predictable ways - can help explain patterns associated with regeneration and the evolution of regenerative capacities across a breadth of taxa.
