EAGER: Individual variation in mast seeding patterns

A common reproduction strategy of perennial plants is called "mast seeding", the intermittent and synchronous production of abundant seed crops across years by a population. The rare and high reproduction "mast" years have cascading effects on food webs within ecosystems, as seeds are a food source for a variety of bird, mammal, and insect species. Evolutionarily, it is thought that this pattern of producing low numbers of seeds for several years, followed by a mast year is a way to keep seed predator populations low, in order to have higher chances for seeds to establish. Another hypothesis is that individuals reproducing at the same time will have higher pollination efficiency, which will lead to more seeds being produced. The critical components of mast seeding are years with high reproduction followed by years with low seeding, and all individuals in the same region doing the same thing. Although studies of individuals in masting populations are rare, some have shown considerable variation in reproductive patterns within a population. Some individuals do not mast at the same time as the rest of the population. This project will build on a unique individual-based dataset of hundreds of white spruce trees to investigate patterns of reproduction by individual plants, and to test the consequences for individuals that have different patterns of reproduction from others in their population. Understanding fluctuations in plant reproductive investment is a key challenge in ecology, conservation, and management. White spruce is an economically valuable species, and this project may have consequences for its management. Additionally, both undergraduate and graduate students will be trained in science and communication. Individual variation has impacts on population and community stability, and individual variation in mast seeding has relevance to forest regeneration and higher ecological levels of organization. Field data will be collected on annual cone production from ~900 trees, extending an existing dataset to eight years. Cones from a subset of trees will be assessed for cone size, seed number, and germination success to test fitness consequences of reproductive patterns relative to when high reproduction occurs locally. Resource allocation and mast seeding will also be examined in the context of surviving an insect attack. Growth and reproduction of individual trees leading up to an insect outbreak will be measured, to test if individuals that allocated energy differently from the population have a higher likelihood of survival. This project will provide empirical data, new insights, and a novel approach into understanding the magnitude of individual variation and its consequences in a mast seeding system.