Dimensions US–China: Collaborative Research: Consequences of diversity in Asian and American tree syngameons for functional variation, adaptation and symbiont biodiversity

The world's approximately 425 oak species maintain species identity even while exchanging genes with their close relatives through hybridization. This history of evolution and genetic exchange has shaped the biodiversity of northern hemisphere ecosystems. Oaks are ecologically diverse, with related species often growing in close proximity but specializing on areas of the forest landscape that differ in soil texture and moisture level or in the frequency of natural fires. Gene exchange can move such ecological specializations between oak species, broadening their ranges and ability to respond to climate change. The impacts of these genetic exchanges may extend beyond the oaks themselves. Oaks host an estimated 1000 gall wasp species worldwide and highly diverse communities of fungi associated with their roots (as mycorrhizae) and inside their leaves (as endophytes). Using paired field surveys and common garden experiments the PIs will evaluate the effects of hybridization and introgression on the genetic, phylogenetic, and functional diversity of focal oak species and their symbionts in the US and China. This work will also provide inquiry-based K-12, undergraduate, and graduate education; critical natural history training to the public through a community-science initiative in oak phenology; and publications that will bring research to public audiences.

Two interdisciplinary teams of researchers, one based in the US and one in China, will investigate how genomic, functional, and phylogenetic diversity of oak trees shape the mycorrhizal fungi, endophytic fungi, and gall wasp and other insect communities that associate with them. Research will focus on two related groups of interbreeding species: bur oak (Quercus macrocarpa) and relatives in the US and bao li (Quercus serrata) and relatives in China. The project has three objectives, each conducted in parallel in China and the U.S. In Objective 1 the teams will perform range-wide phylogenomic surveys of natural populations to reconstruct genomic mosaics, characterize geographic patterns of leaf functional traits, and characterize functional and phylogenetic diversity of associated mycorrhizal fungi, leaf endophytic fungi, and gall wasps. In Objective 2 common gardens will be planted across climatic gradients to evaluate the effects of genetic variation and population differentiation on oak functional and spectral traits and relative fitness in different climates, and how these influence the phylogenetic and functional diversity of oak-associated fungal and insect communities. In Objective 3 the teams will use a second set of common garden experiments to evaluate how plant community and phylogenetic diversity affects focal oak species genetic, phylogenetic, and functional diversity. The project will provide an integrative perspective on how oak diversity within and among species impacts the broad diversity of oak-dominated ecosystems across the northern hemisphere.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.