Can individual responses to environmental variation contribute to the formation of new species?

Abstract

We are investigating whether environmentally-induced variation in body size can prevent mating in threespine stickleback fish. We are investigating this possibility in several recently-established lake populations in which both marine and freshwater stickleback co-occur during the breeding season. With a combination of field observations and experiments, we aim to determine whether growing up in different environments (ocean vs. lake) leads to differences inn body size, which then prevent the two types of fish from recognizing one another as mates. This barrier to reproduction can help explain why the two populations are quickly diverging, and would place them in the early stages of forming new species.