Pollination Ecology of Pedicularis punctata Decne. (Scrophulariaceae) in the Kashmir Himalaya

Abstract The pollination ecology of Pedicularis punctata was studied in the Pir Panjal Range of the Kashmir Himalaya in the summer of 1989. Its nectarless, rostrate, long-tubed flower was found to be pollinated exclusively by Bombus foragers vibrating pollen while the stigma contacted pollen in the pollinator's cervical crevice. Workers of Bombus tunicatus and B. flavothoracicus comprised 95% of its pollinators. Pollen-foraging fidelity of its pollinators was greatest where diversity of Bombus -pollinated plant species in three plant communities was least. Foragers on other plants carried virtually no Pedicularis pollen. P. punctata is a mid-season blooming species similar in its pollination syndrome to comparable species in other geographic regions. The enigmatic function of its long, nectarless corolla tube, even more exaggerated in other Asiatic species, requires further investigation.     

THE POLLINATION DYNAMICS OF SYMPATRIC SPECIES OF PEDICULARIS (SCROPHULARIACEAE)

Sympatric populations of Pedicularis oederi, P. cystopteridifolia, and P. groenlandica on the Beartooth Plateau (Montana) were obligately dependent on Bombus pollinators. Their corolla colors were mutually distinct to insect vision, but their nectars had identical sugar components. Analysis of corbicular pollen loads of pollinating insects indicated a high degree of polylecty. Queen/worker ratios of pollinators on plant species corresponded to the parallel phenological sequences of plant blooming and insect caste development. The total number of individual pollinators of each Bombus species on all plants was directly related to the number of plant species it pollinated, but a comparable relationship between the number of pollinators on a plant species to the number of Bombus species pollinating it was not found. Morphological and behavioral correspondence of floral mechanisms and pollinators form an integral part of the general pattern of coadaptive evolution of the floral ecology of Pedicularis in North America known from previous studies. Reproductive isolation between Pedicularis species in this study is attributed to internal barriers. Wide overlaps of blooming seasons, proboscis lengths of bumblebee species and castes, and pollinator species on Pedicularis species suggest resource sharing, rather than resource partitioning or competition for resources among plant and insect species and individuals.     

POLLINATION ADAPTATION IN PEDICULARIS GROENLANDICA

Cinematographic and stereophotographic records indicate that Pedicularis groenlandica is pollinated in the Colorado Front Range by seven species of pollen-foraging bumblebees (Bombus sp.) to which the nectarless flower is intricately adapted functionally and structurally. Removing pollen by wing vibrations of an oscilloscopically identified frequency significantly distinct from flight vibration frequency, foragers carried pollen loads with up to three foreign pollen types in addition to Pedicularis pollen, which was found in all loads. No direct correlation was evident between flight vibration frequency and combined body-pollen load weight, ambient air temperature, or forager species. The flower is phenologically and morphologically adapted to the worker caste of apparently any Bombus species available to it throughout the plant's montane-alpine zone vertical-distribution range. The evolutionary position of the pollination mechanism is considered in relation to the floral morphology of other species in the genus Pedicularis.     

THE POLLINATION ECOLOGY OF PEDICULARIS ON MOUNT RAINIER

Six native species of Pedicularis in Mount Rainier National Park in Washington State were studied for their reproductive relationships with animal pollinators. Cinematographic and stereophotographic records revealed pollination of the nectariferous P. bracteosa and P. rainierensis by upright, nectar-foraging queens and workers of five bumblebee (Bombus Latr.) species and by inverted workers scraping pollen from anthers concealed within the corolla galea. The nectarless, rostrate flowers of P. contorta, P. groenlandica, P. ornithorhyncha, and P. racemosa were pollinated by pollen-foraging workers and occasional queens virbrating pollen from concealed anthers. Insect exclosure methods revealed complete absence of fruiting in the absence of insects, and pollinator collections further indicate obligate dependence of the plants upon bumblebees for their sexual reproduction. Analysis of corbicular pollen loads from pollinators suggested that pollinator species are not monolectic but that individual pollinators range from monolectic to polylectic. Measurements indicated limited correlations between lengths of corolla tubes and tongues of nectar-foraging insects. Each nectarless Pedicularis species occupied a different, specific habitat, but P. bracteosa and the endemic P. rainierensis were sympatric in part. Each species had a unique spectral reflectance pattern from the corolla. Proximity of habitats and overlap of blooming periods of all Pedicularis species eliminate the possibility of contemporary geographic or phenological reproductive isolation. It is suggested that behavioral interactions of the plants and their insect pollinators may have been instrumental in the past in reproductively isolating these species, hybrids of which are unknown.     

Pollination Ecology of Pedicularis megalantha D. Don (Scrophulariaceae) in the Himachal Himalaya

Abstract In the summer of 1990, the pollination ecology of Pedicularis megalantha was studied in the montane-subalpine spruce-fir forest zone (2750-3050 m) on the north slope of Mt. Huttoo at Narkanda, Himachal Pradesh, in the Indian Himalaya. Its yellow, long-tubed, nectarless flower with a curled rostrum overarched by a broad, inverted lower corolla lip was pollinated exclusively by Bombus albopleuralis and B. tunicatus workers hanging inverted from the corolla and vibrating pollen from introrse anthers concealed within the galea and releasing pollen through a small ventral opening in the galea base. The stigma, protruding from the tip of the rostrum, contacted pollen deposited on the ventral side of the insect's thorax. Corbicular pollen loads from P. megalantha pollinators indicated equal numbers of monolectic and oligolectic foragers. P. megalantha appeared to suffer from competition for pollinators by Cynoglossum wallichii at one site but to be favored in a mixed plant community with nectariferous species offering a forage resource complementary to Pedicularis pollen. As in P. punctata , the long, nectarless corolla tube of P. megalantha appears to function in extending the rostrate vibration pollination mechanism beyond the plant's foliage, which would interfere with its function. It is not an adaptation for nectar-foraging lepidopteran pollinators. P. megalantha was also found to be a root hemiparasite.     

THE POLLINATION ECOLOGY OF DICENTRA CUCULLARIA

In northeastern Iowa and southwestern Wisconsin the flowers of Dicentra cuculiarla were found to be pollinated almost exclusively by Bombus bimaculatus nectar-foraging queens, which were phenologically synchronized in their emergence from hibernation with the flower's anthesis. Cinematographic and stereophotographic evidence indicated that pollen transfer was effected by the ventral side of the insect's head and anterior thorax contacting essential flower parts and to a lesser degree by the front and middle legs contacting pollen-laden edges of the inner petals. Lepidoptera, Diptera, and small Hymenoptera occasionally encountered on the flowers were ineffective in pollination. Abundant Apis mellifera pollen-foraging workers regularly effected pollination, but being an introduced species it exhibits no naturally developed pollination adaptation to the flower. Nectar spur perforation by B. affinis nectar-foraging queens did not affect plant fertility, and this behavior was related only in part to forager tongue length. Nectar-foraging behavior of B. bimaculalus queens on the flowers was correlated with the phenological development of the annual insect colonies.     

A Preliminary Study of the Pollination Ecology of Pedicularis (Scrophulariaceae) in Japan

Abstract An introductory study of the pollination ecology of six Japanese species of Pedicularis conducted in 1982 and 1983 indicated a close parallel between characteristics of floral mechanisms in Japan and those previously investigated in North America. Floral color, floral form, total dissolved solids in floral nectar, and polinator behavior on flowers of Japanese species are similar to those of North American species. Blooming phenology of Japanese species also corresponds to the North American sequence of long-tongued, nectar-foraging queen bumblebees (Bombus Latr.) pollinating nectariferous , earlier-blooming species nototribically and short-tongued, pollen-foraging workers pollinating nectarless, rostrate flowers of later-blooming ones sternotribically. Electrofocus analysis of peroxidase systems in two Japanese species indicated considerable intrapopulational heterozygosity. Nectar component analysis of two transboreal species indicated intraspecific differences in kinds of sugars between widely disjunct Japanese and North American populations. A tentative conclusion is that the Japanese and North American Pedicularis floras have evolved in a parallel manner from Himalayan migrants, while their transboreal elements are in process of vicariant diversification.     

Pollination Ecology and Endemic Adaptation of Pedicularis howellii Gray (Scrophulariaceae)

Abstract Pedicularis howellii , endemic to the Siskiyou Mountains of California-Oregon, is a root hemiparasite obligately dependent upon bumblebee pollinators that remove pollen by vibration from its short-tubed, nectarless, rostrate flowers, which reflect visible and ultraviolet (360nm) light attractive to Bombus foragers. All six Bombus species in the study area pollinated the plant, but only on P. howellii and P. racemosa were B. mixtus workers the most abundant pollinators among the seven bumblebee-pollinated plants studied, including Delphinium decorum, Dodecatheon jeffreyi, Penstemon newberryi, P. shastensis, and Phacelia heterophylla. Analysis of corbicular pollen loads of Bombus pollinators indicated that pollen foragers on Pedicularis species were less pollen-constant than all other bumblebee pollinators. Although P. howellii and P. racemosa blooming periods overlapped slightly, phenological isolation of blooming periods of plants sharing the same pollinators was not evident. Chemical soil analysis of its habitat and quadrat analysis of the population structure of Pedicularis howellii indicated that the plant grows in a moderately fertile forest soil and is restricted to the edge of forest canopy openings where sunlight favors development of plants to the flowering stage. The endemism of P. howellii is related to a similar "edge effect" survival of P. furbishiae in a boreal forest riparian habitat previously studied.     

POLLINATION ADAPTATION IN PEDICULARIS CANADENSIS

During the spring of 1966 and 1967, operation of the pollination mechanism of Pedicularis canadensis L. flowers by nectar- and pollen-foraging bumblebee (Bombus Latr.) queens was observed in an Iowa relict prairie and was recorded by high-speed cinematography. The stigma and style were found to sweep the forager's pronotum crevice as head and tongue were introduced into the 12-mm corolla tube. Pollen deposited in the crevice was not removed as the forager's middle leg only groomed pollen laterally deposited on head and scutum. Thirty corbicular pollen loads from 417 foragers collected on nine prairie plant species included pollen from Pedicularis canadensis, Aquilegia canadensis L., Dodecatheon meadia L., and two unidentified plants not found in the prairie. The pollination mechanism was considered closely adapted morphologically and phenologically to bumblebee queens of eight species found foraging on Pedicularis.