Pollination Ecology ofPedicularis palustrisL. (Scrophulariaceae) in North America

Publisher Website
Google Scholar
Abstract
Field collections and measurements of corolla tubes andBombustongues indicated thatPedicularis palustris, an early summer‐blooming plant on Ile aux Grues and Ile aux Oies in the St. Lawrence River, Canada, is pollinated nototribically by queens of four species of bumblebees foraging for nectar and sternotribically by three species ofBombusworkers scraping pollen from anthers concealed in the galea. Short‐tongued workers ofB. terricolasecured nectar by perforating the base of the corolla tube dorsally or ventrally and, in some cases, pollinated the flower while robbing nectar. The flowers are insect‐dependent for pollination and are almost exclusively bumblebee‐pollinated. Sugar concentration of nectar, determined by refractometry, ranged from 8.0% to 19.5% (mean = 13.9%), and fructose and sucrose components of nectar samples from North America and the Netherlands were detected by thin‐layer chromatography. Excavated roots ofPedicularis palustrisconfirmed its root‐hemiparasitism. Parallel pollination studies were carried out onHypericum perforatumandVicia craccaon the mainland in the same area which bloomed later thanPedicularisand were pollinated primarily byBombusworkers. Predominance of queen pollinators onPedicularisand worker foragers onHypericumandViciaand analysis of corbicular pollen loads of foragers suggest a phenological relationship betweenPedicularis palustrisand the annual reproductive cycle of its bumblebee pollinators previously derived from investigations of other North American and Japanese species.