Causes and consequences of prolonged dormancy for an iteroparous geophyte, Silene spaldingii

1. Prolonged dormancy, during which a plant does not produce above-ground shoots during one or more growing seasons, is common in temperate herbaceous species, but its role in life history is poorly understood. 2. We analysed stage transitions to determine the consequences of prolonged dormancy for Silene spaldingii, a perennial geophyte of semi-arid grasslands in the Columbia Basin of western North America. We monitored 179 S. spaldingii plants from 1987 through 2005, and analysed demographic rates as a function of plant state and seasonal precipitation. 3. Dormant plants had similar survival and growth to vegetative plants, and were more likely to flower in the following year, resulting in a greater reproductive value being associated with the dormant state. Thus, prolonged dormancy is likely to increase fitness in S. spaldingii. 4. Both external (precipitation) and internal (stage in previous year) factors were associated with S. spaldingii vital rates. Prolonged dormancy was more likely following flowering than after being vegetative, and following a wetter summer and/or drier fall the previous year. 5. Our results suggest that geophytic species may respond to current resource availability in a manner dependent on internal state (previous performance) and suggest that prolonged dormancy plays a role in resource allocation and life history.