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

Abstract

Summary 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.