Dissertation Research - Cascading Speciation in a Parasitoid Wasp

University Of Notre Dame, Notre Dame IN

Investigators

Abstract

This project will explore a "cascading" speciation event involving the apple maggot fly (Rhagoletis pomonella) and a parasitoid wasp (Diachasma alloeum) that hunts and consumes the fly's larvae. Populations of both of these organisms have made a shift from their ancestral host, the hawthorn tree, to introduced European apples. Past work has shown that this shift has resulted in the formation of apple- and hawthorn-associated "races" of R. pomonella, each adapted to their respective hosts. It is believed that these races are a first step towards formation of distinct species. This project will look for evidence of a parallel race formation in D. alloeum through differences in wasp life history, behavior and genetics. The broader significance of this research is that it will help to form a more complete understanding of the processes underlying biodiversity. Phytophagous (plant-feeding) and parasitic insects are the most diverse organisms on Earth. One of the unifying goals in biology involves uncovering the sources of this spectacular diversity. Studying the evolutionary dynamics of such a tight ecological network of plants and insects should make clear some of the processes through which natural selection acts to create new species. Furthermore, this work will be of general interest to evolutionary biologists because it involves speciation in the absence of geographic isolation, an event for which few conclusive examples exist.