The Role of Geographically Structured Coevolution in Long Term Diversification: A Test Using Joshua Tree and its Pollinator Moths
Coevolution is an important driver in species interactions. We already know that it can drive diversification in morphology and ecology among more-or-less isolated populations in ecological time. An important next question is whether this variation persists in such a way as to contribute to generating species diversity, or if it is lost amidst changing ecological context. This project provides a first test of this question. It uses the obligate, beneficial relationship between the well-known Joshua Tree and its exclusive pollinators, two yucca moth species. These moths occur either alone or coexist in different parts of the joshua tree range. It is an excellent model because the association has persisted for a very long time, and plant and moth traits have diversified between and within the species. Furthermore, the geographic range of joshua tree is highly fragmented and has a well-understood history of variable connectivity during past climate regimens. Specifically, the project will use molecular and morphological data to test predictions about historical gene flow, current isolation, and morphological variation. Together they can provide strong answers to the question about the role of coevolution in driving speciation.
The results will be of immediate broader utility in conservation biology, as the answers would affect genetically informed conservation strategies, and in climate change biology, where yuccas are sensitive indicator species. Being a species of great public interest and a symbol of the Mojave desert, and a key species for maintenance of desert communities, the results will have immediate application for public agencies. In a broader educational context, yuccas and yucca moths figure prominently in textbooks, and in public education settings such as science centers and parks. The project will further outreach in these areas, and provide public and ranger education in parks and monuments.