Life history trade-offs in a rare orchid: The costs of flowering, dormancy, and sprouting

We tested for life history trade-offs among dormancy, sprouting, and flowering in a seven-year study of a threatened, perennial plant, the small yellow lady's slipper orchid (Cypripedium calceolus ssp. parviflorum (Salisb.) Fernald). The aboveground states of 629 genets were monitored over seven years in a wet meadow in northeastern Illinois, USA. With mark-recapture statistics, survival, resighting, and stage transitions were calculated among three stage classes of individuals: dormant, vegetative, and flowering. The best-fit and most parsimonious models suggested that (1) survival was constant among years, but varied by stage; (2) dormant individuals suffered significantly higher mortality and were more likely to become dormant in future years than sprouting or flowering individuals;, (3) flowering individuals had significantly higher survival and were more likely to flower in the future than sprouting and dormant individuals; and (4) sprouting individuals had a significantly higher stage transition to dormancy from the vegetative state than to any other state. Thus, our results identified costs of dormancy and sprouting to survival and future reproduction, but no costs of reproduction either to survival or future flowering effort. Dormancy seems unlikely to be adaptive except perhaps as a bet-hedging strategy under catastrophic conditions. Applying mark-recapture models to test predictions from life history theory provided a robust means to explore hypothetical trade-offs that may not have been observed in a conventional analysis and allowed dormancy to be estimated robustly without biasing survival estimation.