European Skipper butterfly (Thymelicus lineola) associated with reduced seed development of Showy Lady's-slipper Orchid (Cypripedium reginae)

Abstract

It has been suggested that European Skipper butterflies (Thymelicus lineola) trapped in the lips of the Showy Lady's-slipper orchid (Cypripedium reginae) may interfere with pollination. This could occur through blockage of the pollinator pathway, facilitation of pollinator escape without pollination, and/or disturbance of the normal pollinators. A large population of the orchid at an Ottawa Valley site provided an opportunity to test the interference hypothesis. The number of trapped skippers was compared in 475 post-blooming flowers with regard to capsule development and thus seed development. The presence of any skippers within flowers was associated with reduced capsule development (P = 0.0075), and the probability of capsule development was found to decrease with increasing numbers of skippers (P = 0.0271). The extent of a negative effect will depend on the abundance of the butterflies and the coincidence of flowering time and other factors. Counts of skippers trapped in flowers were found to follow closely a negative binomial distribution (P = 0.8656).