SG: Migrants as mutualists: impacts on plant spread at stopover sites

Each year, animals across the world migrate, often traveling thousands of miles. These migrants include grey whales, wildebeest, monarch butterflies and sandhill cranes. And just like a family on a long road trip across the country, an animal on its annual migration has to stop and refuel along the way. Although the time spent at these ‘stopover’ sites is relatively short, it is incredibly important. Migrating animals need to rest and regain energy (by feeding on local animals and plants) before continuing their journey. Migrating animals also play an important role for many local plants during these visits. Migrating animals like birds, bats and insects that feed on nectar can move pollen around, helping plants reproduce. And migrating animals that eat fruit can help seeds within those fruits move to new locations. This project aims to understand how visits by migratory animals affect plants at stopover sites. How do visits by migrants affect how fast plant populations can grow and spread locally? And what happens if migrants stop coming? Will the plant populations cope with the change, or will they decline either slowly or rapidly? This project will use computer-based models to understand patterns. Familiarity with computers and how to create computer code can be a barrier to this type of research for students studying biology in college. So as part of this project, researchers will work with a local (St. Paul, MN) elementary school to expand access to computers and computer programming using robots. In this project, researchers will develop novel mathematical theory to consider both the beneficial services that migrants provide as well as the costs they extract. Each aim will focus on a different type of mutualistic relationship between migratory animals and plants at stopover sites. Aim 1 considers pollination, where migrants consume nectar (reducing energy to plants) while increasing mating (and thus reproduction) through pollen movement. Aim 2 considers frugivory, where migrants consume fruits (reducing plant fecundity) while increasing germination probability (survival) and dispersal for seeds passed through their guts. Aim 3 considers epizoochory, where migrants consume plants and inadvertently pick up adhesive seeds, thus increasing seed dispersal. The outcome of this research will be predictions as to how sensitive plant population spread is to changes in migratory species and when – if ever – loss of migratory species can promote spread, or even cause population collapse. 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.