Life history of orchids and other wildflowers

Herbaceous perennial plants can live for decades, sometimes for centuries. We study the ways in which plants allocate resources to different life history functions, such as growth, survival, and reproduction, throughout their lives. Much of our research has focused on synchronous flowering (similar to mast seeding in trees), and prolonged dormancy (a phenomenon in which plants spend one or more years entirely below ground). We have also used demographic models to explore the population viability of endangered plant species and the effects of invasive plant species on native wildflowers.

Spatial ecology and conservation of butterflies

Conservation biology is a fundamentally spatial problem. If we want to protect habitat for endangered species, we need to know how they move within and among habitat patches. Movement is also an important part of whether species' can track changing environments. Our research combines an understanding of butterfly population dynamics and dispersal behavior to make concrete recommendations about habitat management and restoration: How much land to protect? Where to protect it? How often to manage with disturbances such as fire and mowing? Our approach is to answer these questions using models based on mechanistic studies of demography and movement. From time to time, we have also collaborated with agencies and citizen scientists to document and predict large-scale responses to climate change.

Population dynamics of social insects

Many species of ants, bees and wasps live in social colonies. Our projects focus on adapting existing frameworks for demographic population models and applying them to social species. This line of research was motivated by interest in pollinator conservation. At the present time, scientists lack a framework for population viability analysis of social insects, which limits our ability to evaluate and predict the effects of conservation options. In addition, the existence of a demographic framework for these taxa will allow us to revisit longstanding questions about the evolution of sociality, using empirically-based demographic models.

Tree seed production and seedling establishment

Mast-seeding occurs when many individual trees of a particular species produce abundant seeds at irregular intervals, leading to "mast" years with high seed production, and “non-mast” years when few seeds are produced. Our research focuses on the physiological causes of synchronous mast-seeding, as well as its consequences for population dynamics of seed and pollen consumers such as mice and bees. We have shown that mast-seeding is an "emergent property" of how plants store resources: If mast years deplete a tree’s stored sugars and carbohydrates, they simply cannot produce seeds in the next year. To date, we have studied various aspects of mast seeding in whitebark pines, European beech, red oaks and sugar maples. Our favorite discovery? The resource costs of seed production affect maple syrup yield; we harvest less syrup in the spring after a mast year.