Color, brightness, and other floral characteristics attracting insects to the blossoms of some Canadian weeds

1973 ◽  
Vol 51 (10) ◽  
pp. 1939-1952 ◽  
Author(s):  
Gerald A. Mulligan ◽  
Peter G. Kevan
Keyword(s):  
Breeding Systems ◽  
Central Portion ◽  
Long Distance ◽  
Outer Portion ◽  
Large Populations ◽  
Pollen Vectors ◽  
Pollinating Insects ◽  
Disturbed Habitats

This paper is concerned with those floral characteristics that appear most important in the long-distance attraction of pollinating insects to the blossoms of weeds: color and brightness of flowers, size of the flower target, and the odor of the flowers. Weed flowers that are occasionally or frequently visited by insects tend to have a higher reflectance in ultraviolet and in blue than do flowers that are rarely visited. The flowers most visited, generally have flower targets over 20 mm in diameter and (or) flowers that are odoriferous. None of these characteristics appears to be of prime importance in determining which kinds of insects visit the flowers of weeds. Many weeds have flowers or flower heads with the outer portion reflecting ultraviolet and (or) blue wavelengths and a central portion absorbing these wavelengths. These flower characteristics, and information on life durations, breeding systems, and pollen vectors are used to evaluate the different strategies that enable weeds to rapidly build up large populations in constantly disturbed habitats.

scholarly journals Camelina (Camelina sativa L. Crantz) Crop Performance, Insect Pollinators, and Pollen Dispersal in the Northeastern US

2019 ◽  
Author(s):  
Richard Rizzitello ◽  
Chuan-Jie Zhang ◽  
Carol Auer
Keyword(s):  
Gene Flow ◽  
Honey Bees ◽  
Pollen Dispersal ◽  
Camelina Sativa ◽  
Genetically Engineered ◽  
Oilseed Crop ◽  
Crop Failure ◽  
Long Distance ◽  
Insect Visitation ◽  
Pollinating Insects

AbstractCamelina sativa (camelina) is an oilseed crop in the Brassicaceae that has been genetically engineered for the production of biofuels, dietary supplements, and other industrial compounds. Cultivation in North America is both recent and limited, so there are gaps in knowledge regarding yield, weed competition, and pollen-mediated gene flow. For these experiments, camelina ‘SO-40’ was grown for three years without weed control. Spring-sown camelina was harvested at 80-88 days with ∼1200 growing degree days (GDD) with yields of 425-508 kg/hectare. Camelina yields were the same with or without weeds, showing competitive ability in low-management conditions. Crop failure in 2015 was associated with delayed rainfall and above-average temperatures after seeding. Camelina flowers attracted pollinating insects from the Hymenoptera, Diptera, Lepidoptera, and Coleoptera. Hymenoptera included honey bees (Apis melifera), mining bees (Andrenidae), sweat bees (Halictidae), bumble bees (Bombus spp.) and leaf cutter bees (Megachilidae). Insect visitation on camelina flowers was associated with modest increases in seed yield. Honey bees comprised 28-33% of all pollinators and were shown to carry camelina pollen on their legs. Air sampling showed that wind-blown pollen was present at low concentrations at 9 m beyond the edges of the field. These experiments demonstrated for the first time that camelina pollen dispersal could occur through honey bees or wind, although bee activity would likely be more significant for long-distance gene flow.

Survival strategies of Silene tatarica (Caryophyllaceae) in riparian and ruderal habitats

2004 ◽  
Vol 82 (4) ◽  
pp. 491-502 ◽  
Author(s):  
Anne Jäkäläniemi ◽  
Anneli Kauppi ◽  
Antti Pramila ◽  
Kalle Vähätaini
Keyword(s):  
Ground Surface ◽  
Survival Strategies ◽  
Long Distance ◽  
Anatomical Structures ◽  
Riparian Plants ◽  
Vascular Elements ◽  
Flat Shape ◽  
Habitat Properties ◽  
Silene Tatarica ◽  
Disturbed Habitats

Certain morphological and anatomical structures of riparian plants might be important for their survival during the season when they are exposed to severe stress caused by flooding, burial, fluctuating temperatures, and drought. These rare characteristics were studied as related to their ecological consequences in a threatened plant, Silene tatarica (L.) Pers., in riparian and ruderal habitats. The main differences between the habitats were morphological and closely related to the habitat properties, whereas the basic anatomy of structures was similar. After sand burial, most riparian plants formed vertical rhizomes and new meristems by bud ramification in the stem base near the ground surface. Special anatomical structures of fleshy underground stems and roots seem to allow plants to be resilient. Moreover, some primitive structures, such as vascular elements with helical and scalariform thickenings, collenchyma, and abundant xylem parenchyma, may increase the resilience of organs. High amounts of saccharose in fleshy rhizomes and roots can increase the cold resistance of plants. The flat shape and structures of tiny seeds may enhance the long-distance dispersal by water. We suggest that the synergism of these structures enables the survival of S. tatarica in highly disturbed habitats with fluctuating water levels.Key words: bud clusters, burial, flooding, growth habit, tensile strength, vertical rhizome.

scholarly journals Pollination by hoverflies in the Anthropocene

2020 ◽  
Vol 287 (1927) ◽  
pp. 20200508 ◽  
Author(s):  
Toby Doyle ◽  
Will L. S. Hawkes ◽  
Richard Massy ◽  
Gary D. Powney ◽  
Myles H. M. Menz ◽  
...  
Keyword(s):  
Crop Protection ◽  
Ecosystem Functions ◽  
Anthropogenic Change ◽  
Migratory Species ◽  
Long Distance ◽  
Pollination Services ◽  
Relative Contribution ◽  
Or Groups ◽  
Large Populations ◽  
Global Food

Pollinator declines, changes in land use and climate-induced shifts in phenology have the potential to seriously affect ecosystem function and food security by disrupting pollination services provided by insects. Much of the current research focuses on bees, or groups other insects together as ‘non-bee pollinators’, obscuring the relative contribution of this diverse group of organisms. Prominent among the ‘non-bee pollinators’ are the hoverflies, known to visit at least 72% of global food crops, which we estimate to be worth around US$300 billion per year, together with over 70% of animal pollinated wildflowers. In addition, hoverflies provide ecosystem functions not seen in bees, such as crop protection from pests, recycling of organic matter and long-distance pollen transfer. Migratory species, in particular, can be hugely abundant and unlike many insect pollinators, do not yet appear to be in serious decline. In this review, we contrast the roles of hoverflies and bees as pollinators, discuss the need for research and monitoring of different pollinator responses to anthropogenic change and examine emerging research into large populations of migratory hoverflies, the threats they face and how they might be used to improve sustainable agriculture.

SPECIALIZED STRUCTURE IN THE REGION OF THE FLAGELLA TUFT IN SPIRILLUM SERPENS

1963 ◽  
Vol 9 (3) ◽  
pp. 393-401 ◽  
Author(s):  
R. G. E. Murray ◽  
A. Birch-Andersen
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Uranyl Acetate ◽  
Central Portion ◽  
Peripheral Plasma ◽  
Outer Portion ◽  
Outer Border ◽  
Specialized Structure ◽  
Pass Through ◽  
Degree Of Extension

Sections of Vestopal embeddings stained with uranyl acetate show that the flagella originate within the plasma membrane of Spirillum serpens. The tuft or bundle of flagella originate as a knob just inside the plasma membrane and pass through the membranes individually but in a defined area. Immediately surrounding this area, and extending over the rest of the end of the cell, a fine polar membrane lies parallel to and about 200 Å inside a somewhat accentuated plasma membrane and the two are linked by delicate bars. Over this region the outer portion of the cell wall loses its usual waviness; under this region the ribosomes in the cytoplasm do not approach as closely as they do to the peripheral plasma membrane, and this retreat is even more extensive in the central portion beneath the area of insertion. The central portion is generally free of membranous organelles and of nucleoplasms; mesosomes or membranous intrusions are commonly found outside the outer border of the polar membrane. The degree of extension of the flagella bases and connection with the described structures remain unknown.

Breeding Systems of Disjunct Populations of Christmas Bells (Blandfordia grandiflora R.Br., Liliaceae): Variation in Self-Fertility and an Ovular Mechanism Regulating Self-Fertilisation

1993 ◽  
Vol 41 (1) ◽  
pp. 35 ◽  
Author(s):  
M Ramsey ◽  
N Prakash ◽  
S Cairns
Keyword(s):  
Seed Set ◽  
Pollen Tubes ◽  
Breeding Systems ◽  
Seed Abortion ◽  
Self Incompatibility ◽  
Coastal Plants ◽  
Hand Pollination ◽  
Disjunct Populations ◽  
Pollen Vectors ◽  
Blandfordia Grandiflora

The breeding systems of disjunct tableland and coastal populations of Christmas bells were determined using hand-pollination experiments. In both populations, 90% or more of self-pollinated plants produced seeds. Tableland plants were significantly more self-fertile than coastal plants (ratio of self seed set to cross seed set: tableland, 0.55 ± 0.03; coast, 0.08 ± 0.02). Significant variation among plants for self-fertility was found in both populations. Autofertility was 1.6% or less in both populations indicating that pollen vectors are necessary for seed set. Seed set by agamospermy in both populations was less than 0.1%. Percentage seed abortion was greater in self-pollinated plants than cross-pollinated plants in both populations. In both self- and cross-pollinated plants, seed abortion was twice as great in the coastal population than in the tableland population. No evidence was found for stigmatic or stylar self-incompatibility. Self and cross pollen adhered to and germinated equally well on stigmas in both populations (72 - 77% germination). Similarly, there were no differences between pollination treatments or populations in the percentage of ovules penetrated by pollen tubes (82 - 89% penetration). When self-pollination preceded cross-pollination by 24 h or longer seed set was significantly reduced compared to flowers that were cross-pollinated only, suggesting ovules were pre-empted by self pollen tubes. Collectively these results strongly suggest that self seed set was reduced by a mechanism operating at the ovule level, such as early-acting inbreeding depression due to recessive seed-aborting genes, although incomplete late-acting self-incompatibility cannot be ruled out. For coastal plants, this ovular mechanism largely prevents selfing, indicating plants were predominantly outcrossing although most produced some self seed. For tableland plants, substantial seed set by selfing may occur under natural conditions.

Visual and olfactory floral cues related to ambophilous pollination systems in Poaceae

2019 ◽  
Author(s):  
Isadora Schulze-Albuquerque ◽  
Ana Carolina Galindo Da Costa ◽  
Paulo Milet-Pinheiro ◽  
Daniela Maria Do Amaral Ferraz Navarro ◽  
William Wayt Thomas ◽  
...  
Keyword(s):  
Grass Species ◽  
Wind Pollination ◽  
Pollen Vectors ◽  
Pollinating Insects ◽  
Floral Visitors ◽  
Pollen Vector ◽  
Pollination Systems ◽  
Chloris Barbata ◽  
Floral Cues

Abstract Usually considered anemophilous, grasses (Poaceae) have been the subject of few studies that recorded insects visiting their flowers. Such visitors, with wind, could act as pollen vectors in a possible ambophilous system. Since colour and scent are floral cues attracting pollinating insects, we aimed to provide the first insights into how these cues could be involved in the attraction of pollinators by grasses. Chloris barbata, Paspalum maritimum (with two morphotypes), P. millegrana and Urochloa plantaginea were studied. We determined the role of each pollen vector (wind and insect) and we registered the frequency of floral visitors. Also, we characterized the colour reflectance of glumes, anthers and stigmas and we determined the colour space in the bee colour hexagon and the chemical composition of floral scents. The floral structures of each species reflect colour differently and are perceived differently by pollinators. Furthermore, the volatile organic compounds detected are similar to those found in entomophilous species. In two of the grass species, we registered eight species of visitors, including bees, wasps and flies. Overall, wind was the most important vector for reproductive success. Insects, however, may induce wind pollination by creating pollen clouds when they visit inflorescences.

Town Building in North India, 1790–1830

1975 ◽  
Vol 9 (4) ◽  
pp. 483-504 ◽  
Author(s):  
C. A. Bayly
Keyword(s):  
Eighteenth Century ◽  
Urban Communities ◽  
East India Company ◽  
North India ◽  
Medieval Period ◽  
Long Distance ◽  
Early Nineteenth Century ◽  
British Rule ◽  
Large Populations ◽  
Town Building

The fate of urban centres in eighteenth- and early nineteenth-century India has attracted attention far in excess of their supposed importance as population centres. It is assumed that flourishing towns are an indicator of economic development and change in their hinterlands. Muslim historians traditionally laid stress on the opulence of towns as a gauge of the wealth of divisions of the Moghul Empire. Recently, Indian historians of the Medieval period have returned to the theme, claiming for the Moghul cities large populations, developed ‘industries’ and sophisticated credit systems. Throughout these works there is an implicit paralled drawn with the point it is suggested that far from being mere administrative centers and entrepots for ‘aristocratic’ long-distance trade, these cities were exchange marts for wealthy hinterlands where agreculturalists exchanged thier products of ‘urban industries’. It is but a short step to argue that these cities weakened by the anarchy of the eighteenth century, were finally ruined by the negligent commercial amorality of the East India Company. The claim by early British writers that the security of British rule encouraged the growth of urban communities in which merchants secured relief from the vexations of local potentates and innumerable minor transit duties is rejected This argument for town decline first revived by Professor Irfan Habib almost as a throwaway, has recently been followed by other younger Indian Marxist historians.

scholarly journals Spatial and temporal invasion dynamics of the 2014-2017 Zika and chikungunya epidemics in Colombia

2020 ◽  
Author(s):  
Kelly Charniga ◽  
Zulma M Cucunubá ◽  
Marcela Mercado ◽  
Franklyn Prieto ◽  
Martha Ospina ◽  
...  
Keyword(s):  
Zika Virus ◽  
Temporal Dynamics ◽  
Virus Disease ◽  
Geographic Distance ◽  
Geographic Origin ◽  
Gravity Models ◽  
Long Distance ◽  
Spatial Spread ◽  
Invasion Dynamics ◽  
Large Populations

Zika virus (ZIKV) and chikungunya virus (CHIKV) were recently introduced into the Americas resulting in significant disease burdens. Understanding their spatial and temporal dynamics at the subnational level is key to informing surveillance and preparedness for future epidemics. We analyzed anonymized line list data on approximately 105,000 Zika virus disease and 412,000 chikungunya fever suspected and laboratory-confirmed cases during the 2014-2017 epidemics. We first determined the week of invasion in each city. Out of 1,122, 288 cities met criteria for epidemic invasion by ZIKA and 338 cities by CHIKV. We estimated that the geographic origin of both epidemics was located in Barranquilla, north Colombia. Using gravity models, we assessed the spatial and temporal invasion dynamics of both viruses to analyze transmission between cities. Invasion risk was best captured when accounting for geographic distance and intermediate levels of density dependence. Although a few long-distance invasion events occurred at the beginning of the epidemics, an estimated distance power of 1.7 (95% CrI: 1.5-2.0) suggests that spatial spread was primarily driven by short-distance transmission. Cities with large populations were more likely to spread disease than cities with smaller populations. Similarities between the epidemics included having the same estimated geographic origin and having the same five parameters estimated in the best-fitting models. ZIKV spread considerably faster than CHIKV.

scholarly journals Pollination of slipper orchids (cypripedioideae): a review

Lankesteriana ◽  
2013 ◽  
Author(s):  
Robert W. Pemberton
Keyword(s):  
Gravid Female ◽  
Fungal Spore ◽  
Fruit Flies ◽  
Breeding Systems ◽  
Pollination System ◽  
Tropical Asia ◽  
Pollinator Species ◽  
Deceit Pollination ◽  
Pollen Vectors ◽  
Pollination Systems

Cypripedioideae (five genera; ca. 176 species) are widespread in temperate and tropical Asia and America. About a quarter (42) of the species have been studied to determine their pollinators and/or breeding systems. All flowers are one-way traps pollinated by insects of particular types and size. Slipper orchids are selfcompatible and pollinated by deceit. Most Cypripedium species are pollinated by bees, whereas some smallerflowered species are pollinated by flies, and a few are pollinated by both. Most bee-pollinated Cypripedium species appear to be generalized food mimics. The fly-pollinated species have evolved diverse pollination systems that utilize a variety of flies as pollen vectors, including fruit flies, dung flies, and a fungal spore-eating hoverfly (Syrphidae). Most species of the tropical Asian Paphiopedilum and tropical American Phragmipedium are pollinated by hoverflies; flowers of many species in both genera have aphid-like spots that attract gravid female hoverflies that normally lay their eggs in aphid colonies. The more brightly colored Paphiopedilum micranthum and Phragmipedium besseae are pollinated by Hymenoptera. Autogamy is limited but occurs most frequently in Phragmipedium species. About two-thirds of the insect-pollinated slipper orchids (25/37) have evolved highly specialized flowers that are pollinated by a single pollinator or several pollinator species in the same genus. Species belonging to the same taxonomic section usually have the same pollination system. The deceit-pollination system of Cypripedioideae appears to have evolved early in diversification of Orchidaceae.

Dispersal and germination of seeds of Pisonia grandis, an Indo-Pacific tropical tree associated with insular seabird colonies

2005 ◽  
Vol 21 (3) ◽  
pp. 263-271 ◽  
Author(s):  
Alan E. Burger
Keyword(s):  
Seed Dispersal ◽  
Seedling Survival ◽  
Forest Tree ◽  
Long Distance ◽  
High Germination ◽  
Dispersal Vectors ◽  
Large Populations ◽  
Germination Success ◽  
Pisonia Grandis ◽  
Seabird Colonies

The distribution of the forest tree Pisonia grandis (Nyctaginaceae) coincides with seabird colonies on small tropical islands. Its seeds are enclosed in a calyx exuding extremely sticky resin which adheres strongly to feathers. Birds are obviously seed-dispersal vectors, but the multi-seeded infructescences frequently entangle birds, often fatally. On Cousin Island, Seychelles, I investigated the production, germination, survival, and tolerance to seawater of Pisonia seeds, and the occurrence of entanglement with birds. Fresh seeds had high germination success (62–87% in experimental trays), but seedling survival in Cousin's forests was low (0.1% of 6020 seeds survived as seedlings after 2–8 mo). Some seeds tolerated 30 min daily immersions in seawater (8–15% germination after 14–28 d treatment), but not continuous immersion in seawater (reduced germination after 5 d and none after 12 d). Inter-island dispersal is likely via living unencumbered seabirds carrying a few seeds, but not on floating carcasses. Seeds attached to carcasses did not have improved germination or survival. Intra-island propagation is almost entirely vegetative, with negligible local seed dispersal. Pisonia plants therefore do not benefit from fatal entanglements. The extreme stickiness of the seeds evidently evolved to resist removal by seabirds and so facilitate long-distance dispersal. The mortality of some potential vectors is an unfortunate consequence, but has little impact on the large populations of tree- and ground-nesting seabirds which nest in or under these trees.

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