Pollen-Limited Fruit Set in Isolated Patches of Maianthemum canadense Desf. in New Jersey

Abstract

WORTHEN, W. B. AND E. W. STILES (Department of Biological Sciences and Bureau of Biological Research, Rutgers-The State University of New Jersey, Piscataway, NJ 08855-1059). Pollen-limited fruit set in isolated patches of Maianthemum canadense Desf. in New Jersey. Bull. Torrey Bot. Club 115: 299-305. 1988.-We examined the effects of pollen addition and raceme density on fruit set in seven isolated patches of Maianthemum canadense Desf. (Liliaceae; False Lily-of-the-Valley) in central New Jersey. We removed racemes from two of four quadrants in each patch to create distinct high and low density sectors. We hand pollinated all the racemes in four 1-m quadrats (1/quadrant) within each patch, and compared fruit set in these quadrats with fruit set in eight naturally pollinated control quadrats (2/quadrant). We recorded the percentage of racemes that bore fruit and the mean number of fruits/infructescence in each quadrat, and analyzed these data with three-factor analyses of variance (patch, density, and pollination-treatment effects). There was a significant effect of pollen addition on fruit set. In four patches, hand pollination significantly increased both the percent of racemes that bore fruit and the number of fruits/infructescence. We conclude that fruit set in these patches of M. canadense was pollen limited. A previous study reported that fruit set in M. canadense was resource limited, but our results suggest that fruit set in different patches may be limited by different factors. The clonal architecture of a patch and the relatedness and distance between mating plants may influence these patterns. There were no significant density effects, in any patch, on fruit set in hand pollinated or naturally pollinated quadrats. Although this suggests that plant density (and inferentially, competition for resources) did not limit fruit set, clonal growth patterns may confound this conclusion.