Collaborative Research: BoCP-Design: US-China: Functional divergence between females and males: consequences of climate-induced shifts in composition of dioecious plant populations

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Most animals and many plants have separate biological sexes: individuals can be either female or male. In addition to their distinct body plans, females and males often differ ecologically. They may have different dietary needs, different vulnerability to predators, or different responses to climate stress. As the Earth’s climate rapidly changes, scientists predict that females and males will differ in their ability to cope, and this may cause an over-abundance of one sex and a shortage of the other. In this project, the research team will test how climate change will affect the sex ratio of dominant trees and shrubs, and whether changes in sex ratio can influence biodiversity of the community and nutrient cycling through the ecosystem. The project brings together American and Chinese scientists to compare whether these responses to climate change play out similarly in North America and Asia. Many important food and landscaping plants have separate sexes (spinach, pistachio, holly, and willow, for example), so this research will help scientists predict how these and similar plant species will respond to future climate change. In addition, students will be trained via a distributed, five-institution graduate seminar, as well as research experiences for undergraduate and high school students. Functional divergence of the sexes raises the potential for climate change to perturb population sex ratios through contrasting effects on females and males. Little is known about the consequences of sex ratio shifts for populations, communities, and ecosystems. The binational team will develop the foundations needed to understand and forecast the direction and magnitude of changes in sex ratio under global climate change, and to test the cascading effects of climate-induced sex ratio shifts on population viability, host-associated biodiversity, and ecosystem function. The team will develop a comparative system of woody dioecious plants in Sichuan Province, China and Texas, US. Like many dioecious plants, these habitat-forming woody species support diverse micro- and macro-biota that affect ecosystem-level fluxes of carbon and nitrogen. This Design project will bring together the research team for workshops in the US and China to develop theory for the ecological consequences of sex ratio sensitivity to climate change, and to develop the methods and modeling approaches required to test its predictions. The project will support development of molecular markers to identify the sex of non-flowering individuals, DNA barcoding technologies to characterize host-associated communities, and assays of sex-specific soil carbon and nitrogen dynamics. Dioecy is among the most common forms of demographic structure and climate change is expected to alter female:male sex ratios. This project is among the first to evaluate how functional divergence of the sexes and climate-induced changes in sex ratio lead to cascading effects across scales of organization.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.