Population viability analysis of Cypripedium calceolus in a protected area:: longevity, stability and persistence

Cypripedium calceolus L. is an emblematic long-lived clonal orchid which has suffered an alarming decline throughout Eurasia. We performed a population viability analysis on three island populations in a protected area to estimate population viability and thus to gain a better understanding of the species and its needs. We developed a 10-stage matrix model, comprising the seed bank, the first 4 years underground, juveniles, young and adult clump stages and three dormant stages, from an 11-year census. All analyses indicate that the three populations have remarkably slow and stable dynamics, with stochastic growth rates close to 1 after 100 years and very slow convergence to equilibrium. The system is probably stabilized by the long life span of clumps (mean longevity from 110 to 350 years). Retrospective and perturbation analyses showed that adult dormancy had an important role in the dynamics, and adult survival and seed persistence were key factors in maintaining population stability and persistence. A young, uniformly distributed population had fewer, shorter lived adult clumps than two older, aggregated populations. Although no perceptible change was predicted for the next 100 years, the younger population was more sensitive to environmental variations and may go extinct in the next 250-500 years, depending on longevity of the seed bank. C. calceolus populations can persist in a protected area where there are only slow changes in habitat through secondary forest succession. The dramatic decrease in C. calceolus population size and area over 20 years in Eurasia suggests that many populations have experienced unforeseeable extrinsic disturbances or unfavourable habitat disturbances. Our Population Viability Analysis indicated the importance of habitat vs. individual conservation for the protection of C. calceolus populations. As this species is usually found within rich orchid communities, it should be used as an umbrella species in management plans.