Peter G. Kevan

Pollinators as bioindicators of the state of the environment: species, activity and diversity

Pollinators and pollination are crucial in the functioning of almost all terrestrial ecosystems including those dominated by agriculture because they are in the front line of sustainable productivity through plant reproduction. Pollinators are bioinidicators as individuals and populations in that they can be used to monitor environmental stress brought about by introduced competitors, diseases, parasites, predators as well as by chemical and physical factors, particularly pesticides and habitat modification. Honeybees are useful as samplers of the environments in which they are kept and have been used to assess atmospheric and other types of pollution. Pollinator guildes offer new means of assessing ecosystemic health because the species diversity and abundance relationship is changed from the log-normal standard expected from ecological principles and niche theory. ©1999 Elsevier Science B.V. All rights reserved.

Truelove Lowland, Devon Island, Canada: A High Arctic Ecosystem

This book summarizes the research conducted within the Canadian component of the International Biological Program. The area studied covers 16 square miles, an oasis in these northern lands, unusually rich in flora and fauna. Much of the basic information learned from the studies can be applied to all arctic island land management plans.

Sun-Tracking Solar Furnaces in High Arctic Flowers: Significance for Pollination and Insects

Heliotropic flowers (Dryas integrifolia, Papaver radicatum) act, in sunshine, as solar reflectors, their corollas focusing heat on the sporophylls. Considerable intrafloral temperatures are generated. Winds above 3.8 meters per second and cloud abolish the effect. Insects that bask in the flowers also gain heat. The phenomena areimportant in maximizing the small heat budget.

The Economic Impacts of Pollinator Declines: An Approach to Assessing the Consequences

Since agricultural activities were first recorded, there have been shortages of pollinators. Today it seems that pollination systems in many areas of agriculture are threatened by the inadequacy or lack of

SPATIAL FLOWER PARAMETERS AND INSECT SPATIAL VISION

The present article reviews recent and older literature on the spatial parameters that flowers display, as well as on the capacities of anthophilous insects to perceive and use these parameters for optimizing their foraging success. Although co‐evolution of plants and pollinators has frequently been discussed with respect to floral colours and insect colour vision, it has rarely been assessed with respect to insect spatial vision and spatial floral cues, such as shape, pattern, size, contrast, symmetry, spatial frequency, contour density and orientation of contours. This review is an attempt to fill this gap. From experimental findings and observations on both flowers and insects, we arrive at the conclusion that all of the spatial and spatio‐temporal parameters that flowers offer are relevant to the foraging task and are tuned to the insects visual capacities and visually guided behaviour. We try, in addition, to indicate that temporal cues are closely related to spatial cues, and must therefore be included when flower–pollinator interactions are examined. We include results that show that colour vision and spatial vision have diverged over the course of evolution, particularly regarding the processing of spatio‐temporal information, but that colour vision plays a role in the processing of spatial cues that are independent of temporal parameters. By presenting this review we hope to contribute to closer collaboration among scientists working in the vast fields of botany, ecology, evolution, ethology and sensory physiology.

Promotion of weed species diversity and reduction of weed seedbanks with conservation tillage and crop rotation

Abstract In a 6-yr study on four farms (36 fields) in Ontario, Canada, we tested the effects of tillage (moldboard, chisel plow, no tillage) and crop rotations (continuous corn, corn-soybean, corn-soybean-winter wheat) on emerged and seedbank weed species diversity and density. Aside from the imposed experimental treatments, all other management was generally consistent among farms. Tillage had the largest effect on weed diversity and density. No tillage promoted the highest weed species diversity, chisel plow was intermediate, and moldboard plow resulted in the lowest species diversity. These results are consistent with ecological succession theory. The increase in weed species diversity resulted from 20 species being associated with no tillage systems, 15 of which were winter annuals, biennials, or perennials. Emerged weed density was affected only by tillage. Over 6 yr, seedbank declined in no-tillage systems from 41,000 to 8,000 seeds m−3. Crop yields were not affected by tillage or crop rotation. In practical terms, reduced tillage in combination with a good crop rotation may reduce weed density and expenditures on weed management. Nomenclature: Glyphosate; corn, Zea mays L. ‘Pioneer 3902’; soybean, Glycine max (L.) Merr. ‘KG 40’; winter wheat Triticum aestivum L.

DNA barcoding a regional bee (Hymenoptera: Apoidea) fauna and its potential for ecological studies

DNA barcoding has been evaluated for many animal taxa and is now advocated as a reliable and rapid means for species‐level identification. The coming‐to‐light of this identification tool is timely as we are now facing perhaps the greatest rate of species loss in recent millennia. This study contributes to an ever‐increasing number of published accounts of DNA barcoding successfully and accurately distinguishing animal taxa, in this instance, the bee fauna of Nova Scotia, Canada. Most members of this well‐known fauna were resolved with particular clarity; the average intraspecific divergence was less than 0.5%, and COI sequences from over 75% of the provinces species are now in the Barcodes of Life Data System. DNA barcoding also revealed some surprises within this fauna, including the possible recognition of two undescribed genetically unique species, one in the genus Ceratina (subgenus Zadontomerus), the second in the genus Andrena (subgenus Larandrena); both are presently receiving further taxonomic study. In addition, DNA barcoding has allowed sex‐associations among two pairs of cleptoparasitic species. The resulting utility of DNA barcoding for ecological studies of bee communities is discussed.

Why are there so many and so few white flowers

Though the world we see appears to be rich in white flowers, this is not the case for animals, such as insects, with ultraviolet (UV) receptors. In fact, flowers that appear white to insects are very rare. We analyse this phenomenon to highlight new discoveries in the mechanisms of insect vision that may have influenced the evolution of flower colour. Our analysis reveals that an understanding of biological signalling requires a comprehensive understanding of sensory physiology and perceptual psychology. An evaluation of UV signals alone may not be helpful, as this can be as inaccurate as models based solely on the human visual system. We interpret floral colours and their frequency in nature from the more relevant perspective of insect colour vision.

Scent and color, floral polymorphisms and pollination biology in Polemonium viscosum Nutt.

The breeding system and pollination ecology of Polemonium viscosum Nutt. (Polemoniaceae) were investigated on Pennsylvania Mountain in the Colorado Rocky Mountains. Polemonium viscosum is an obligate entomophilous outcrosser. Flowers are slightly protandrous, have spatially separated stigmas and anthers during anthesis and show little self-compatibility. Within populations, corolla color varies from light blue to purple and flowers may be broadly grouped within this spectrum as light blue, blue purple or purple. Differences in the ultraviolet are very small and probably not effective. Two floral scent morphs, sweet and skunky, occur. Differences in pollination biology can be related to these floral polymorphisms. The distributions of the morphs were examined along an altitudinal gradient. The light blue corolla type is significantly more frequent in the partially shaded krummholz locations whereas blue purple flowers are more common in the alpine. These differences may be related to the relative visibility of the two morphs against their respective backdrops. Potentially effective pollinators of Polemonium viscosum include Bombus kirbyellus (B. balteatus) (Hymenoptera: Apidae), H yles lineata (Lepidoptera: Sphingidae), Muscidae (Diptera) and Syrphidae (Diptera). Preliminary results suggest that bumblebees preferentially visit sweet-smelling flowers, whereas H. lineata does not.

The variability in settling velocities of some pollen and spores

Abstract The settling velocity in still air of natural and dyed spores and pollen of several species was measured using the method of McCubbin and was found to be as follows (in cm s-1): black spruce (Picea mariana), 3.19; jack pine (Pinus banksiana), 2.53; Lycopodium, 2.31; dyed Lycopodium, 2.15; oil palm (Elaeis guineensis), 3.00; dyed oil palm, 2.16 and corn(Zea Mays), 30.95. The percentage of clustered spores and pollen was taken into account but was not found to significantly affect settling velocity except in the case of dyed oil palm. Comparisons of the measured settling velocities of clustred grains were made with the model of Ferrandino and Aylor. This was found to be accurate in general, but tended to over-estimate the settling velocity of clumped spores of Lycopodium and of dyed pollen of oil palm.