Dormancy is associated with decreased adult survival in the burnt orchid, Neotinea ustulata

Abstract

1. Prolonged dormancy, a condition in which herbaceous perennial plants do not sprout for more than a year, has only been described to any great extent in long-lived clonal species, particularly in the family Orchidaceae. However, some short-lived, partly clonal or non-clonal perennials also experience dormancy, and their shorter life spans and reduced or absent clonality may change the life history costs and benefits of this phenomenon. 2. We explored the life history context of dormancy in one such plant, Neotinea ustulata. A total of 1013 plants were monitored in five populations across Estonia between 1993 and 2005. Cormack-Jolly-Seber (CJS) and multistate analyses, two statistical methods to estimate demographic parameters in open populations, were conducted to estimate the probabilities of survival, dormancy and state transition among flowering, vegetative and dormant states among the populations. 3. The best-fit CJS model suggested that dormancy varied among populations unpredictably, while survival varied in parallel among populations across time. Mean survival was 0.727 ± 0.115 (± SE) and mean dormancy was 0.543 ± 0.129. 4. Multi-state analyses suggested that survival varied in parallel with life history state across all populations, with flowering plants surviving almost completely (0.999 ± 0.007) and dormant plants being the least likely to survive (0.684 ± 0.042). Vegetative plants were found to be intermediate (0.793 ± 0.051). All plants were likely to revert to a dormant state (range 0.451 ± 0.085-0.812 ± 0.053). 5. Dormancy appears to be maladaptive in N. ustulata, although we suggest that it may still be adaptive as a bet-hedging trait if it results in substantially lower variability in survival and fitness over the long term. We suggest that conservation measures aimed at preserving populations of dormancy-prone plants be linked to censuses focusing on detecting and estimating dormancy levels because high levels of dormancy indicate a low annual survival. © 2006 The Authors.