EAPSI: Plant-herbivore Interactions and Host Race Formation: Reconstructing the Evolution of Chrysochus-Apocynaceae Associations

Mchone Elizabeth E, Philadelphia PA

Investigators

Abstract

The relationships between intercontinental dispersals and the evolution of host plant-herbivore interactions are not well understood, but may offer insight into invasive species ineractions. Two species of dogbane leaf beetles (Chrysochus, Chrysomelidae) possess an adaptation allowing them to feed on the toxic dogbane plants (Apocynum, Apocynaceae) in North America. Eight Chrysochus species live in Asia alongside Apocynum, but the nature of their interactions there, and when and how the association in North America evolved, is unknown. This project will investigate the evolution of the association between Chrysochus and Apocynaceae, focusing on the interactions between the widespread C. chinensis and its multiple hosts. Specimens of Chrysochus and their host plants will be collected in China to identify previously unknown host associations and create an evolutionary tree. Feeding experiments will be conducted on C. chinensis to determine whether separate populations eat different hosts, often an early step toward speciation. Experiments will be supervised by Dr. Huai-Jun Xue, associate professor at the Institute of Zoology (IOZ) in Beijing and expert on the evolution of insect-host plant specialization. Situated within the ranges of several Chrysochus species, the IOZ holds the largest collection of the beetles in Asia, making it the ideal location to investigate their evolution. The award will be used to collect specimens of ten Chrysochus and Platycorynus (a closely related genus) species in five provinces in China. Host plants, other plants in the Apocynaceae, and observations of feeding behavior will be collected in those areas. This work will expand the host association information for the group, and DNA from field-collected and museum specimens will later be sequenced with high-throughput Illumina sequencing to construct the first molecular phylogeny of Chrysochus with complete sampling of species. C. chinensis individuals will be collected in Beijing and fed on several potential host plants in host acceptance and oviposition experiments. Their preference for, and fitness on, the potential hosts will be assessed by proxies such as growth and oviposition rates to determine whether there is evidence for the evolution of host races. This project will contribute to the field of plant-insect interactions, the natural history of an understudied group of organisms, and encourage future cooperation between the Academy of Natural Sciences of Drexel University and the IOZ. This award under the East Asia and Pacific Summer Institutes program supports summer research by a U.S. graduate student and is jointly funded by NSF and the Chinese Ministry of Science and Technology.