Document: RIC-3-37-2

Estimating dormancy and survival of a rare herbaceous perennial using mark-recapture models.

SHEFFERSON, R.P.* ¹, B.K.SANDERCOCK ¹, J.PROPER ² and S.R.BEISSINGER ¹

University of California at Berkeley, Berkeley, California 94720-3110 USA ¹
Lake County Forest Preserve District, Lake Villa, Illinois 60046 USA ²

Abstract:
Mark-recapture statistics have been used predominantly to analyze animal populations, yet their application can be extended to the estimation of plant demographic traits in cases where conventional methods are inadequate. We applied open population mark-recapture models incorporating maximum likelihood techniques to estimate annual probabilities of dormancy (d) and apparent survival (PHI) of the small yellow lady's slipper orchid (Cypripedium calceolus ssp. parviflorum (Salisb.) Fernald), a long-lived, threatened plant that experiences an adult dormant stage that can bias survival estimates. The aboveground states of 548 genets in eight patches were monitored over five years. Dormancy periods of one or two years were most commonly observed, although dormancy periods as long as four years were also observed. The best-fit model suggested that apparent survival was constant throughout the study for all patches, while dormancy varied additively with time among patches. The probability of dormancy was 0.320 0.024 on average, with a maximum bias of 0.067 as calculated using an estimate of the probability of detection. Mean apparent survival probabilities were high in each patch (PHI = 0.878) but dormancy probabilities varied considerably among patches (range: 0.188 to 0.672). Conventional resprouting probabilities underestimated apparent survival by an average difference of 0.288 (range: 0.150 to 0.589). This novel application of mark-recapture statistics to plant demography allowed robust survival estimates that accounted for uncertainty due to an unobservable, dormant life stage.

Keywords: dormancy; mark-recapture; survival; orchids; maximum likelihood

This abstract is being presented at: 2:15 PM in session:
Oral Session #33: Plant Demography.