Pollinator Deception and Plant Reproductive Success in Jack-In-The-Pulpit

Abstract

I conducted a study of the deceptive pollination system of Jack-in-the-pulpit (Arisama triphyllum, Araceae) in forests of west-central Indiana. I focused on (a) determining the identities and abundances of insect visitors to spathes, (b) evaluating the success of female spathes in setting fruit, (c) determining the relative importance of pollinator visitation and plant size for fruit number, and (d) investigating the function of the female spathe’s lack of an exit hole, which has been hypothesized to improve pollination success. I found that (a) Jack-in-the-pulpit receives visits from both flies and thrips. Counts of fly corpses from spathes showed the most prevalent families to be Mycetophilidae and Sciaridae with other nematoceran families and a few brachyceran families present as well. Visitation by thrips, determined by visual inspection of spathes, was low, involving only 30% of plants. (b) Fifty-seven percent of female plants set fruit, with much variation among sites. (c) Mushroom flies, especially the families Mycetophilidae and Sciaridae, were found to be the primary pollinators of Jack-in-thepulpit based on pollen loads, visit rates, and an exclusion experiment. Pollination by thrips, though possible, probably had only a minor effect. (d) An experiment that created an exit hole in female spathes yielded no support for the hypothesis that lack of an exit hole (the natural condition) improves fruit set.