Marcin Zych

Flower-visitor and pollen transport networks in a large city: structure and properties

Plant species and their pollinators are linked by their mutualistic interactions, which form the basis of pollination networks. The use of a network approach allows one to take into account all interactions between a group of plants and its animal pollinators, and to reveal the structure of these connections. We analysed pollination interactions for urban habitat fragments located within the Warsaw city environment. We compared two similar, ruderal communities (phytosociological order Onopordetalia acanthii) located in distant parts of the city of Warsaw (Poland) that differed with the surrounding ecosystems. The aim of this study was to define the structures and properties of flower-visitor (visitation) and pollen transport networks (based on analysis of pollen loads carried by insects) and to assess the differences between the studied sites. Although the sites differed in insect relative abundance (Diptera dominated one study site, whereas Hymenoptera dominated the other), network size and structure were similar for both communities. In both cases, networks contained moderately specialized species (based on H2′ index); however, networks were dominated by apparently ecologically generalized insect taxa as well as those represented by a single specimen. Networks based on pollen transport indicated greater generality of insect species (more links) than those based on our samples of visitation. The most highly linked plant species represented were either the most abundant (Fabaceae) or phenotypically generalized taxa (Daucus carota). We conclude that plant–pollinator interactions in such highly disturbed and isolated habitats are composed mostly of ecologically generalised species. Moreover, we stress the usefulness of pollen load analysis in the development and verification of visitation data.

Fly pollination of dichogamous Angelica sylvestris (Apiaceae): how (functionally) specialized can a (morphologically) generalized plant be?

Because of the flower morphology and high number of insect visitors, plants of the family Apiaceae are regarded as generalists in terms of pollination systems. Recent studies however showed some degree of, at least, ecological specialization in some members of this taxonomical group and indicated interesting patterns of insect visitor behavior: discrimination between umbel sexual phases. To test whether this is true in case of other members of the family, over two years we studied the pollination biology of a common European umbellifer, Angelica sylvestris, a species considered by some authors as a supergeneralist. Although its flowers were visited by over 70 species of insects grouped in 10 morphospecies, only a relatively narrow assemblage of muscoid and syrphid flies, rather constant in both study years, contributed to pollination. These insects did not exhibit any preferences toward plant sexual phases. Based on our results and available literature, we discuss the concept of specialization/generalization of the A. sylvestris pollination system, especially in the context of the “unspecialized” floral morphology characteristic for members of the Carrot family.

What if we lose a hub? Experimental testing of pollination network resilience to removal of keystone floral resources

Abstract On the basis of theoretical predictions, pollination networks seem to be resilient to random node elimination but sensitive to targeted exclusion. However, such predictions have a very weak empirical basis. In order to test the robustness of the pollination network to short-term disturbances, we removed inflorescences of the most connected species occurring in a lowland meadow network using the before–after approach and compared the result with that obtained by network modelling. The manipulated network showed no significant differences for the most commonly used metrics, but was more generalized than control networks, owing to a change in the preferences of pollinators. Furthermore, no secondary extinctions (emigrations) were found, owing to the considerable natural variation found among insect species assemblages. Following elimination of the most linked plant species, a new hub was detected in the experimental meadow, the hub node being a plant species with a similar inflorescence to that removed, and formerly playing the role of a peripheral node. We conclude that exclusion of the main food source forced insects to change their specialized preferences to other plant species that were available. Mostly, these had inflorescences similar to those that were removed.

Investigations of anthocyanins, organic acids, and sugars show great variability in nutritional value of European cranberry ( Vaccinium oxycoccos ) fruit

Increased consumer interest in nutraceutical-rich foods in relation to human health has resulted in the increased use of cranberries in the modern diet. Berries of wild European cranberry clones and cultivars show great variation in yield, colour and quantities of biologically active compounds. In the present study, we estimate the production of different phytochemical components in 40 genotypes of Vaccinium oxycoccos. Our main goal was to identify genotypes that have superior economic attributes, such as high levels of anthocyanins, organic acids and easily digestible carbohydrates. As a result, two wild clones of Lithuanian origin (98-C-17 and 98-C-15), and the Estonian cultivar ‘Maima’ were selected as the most valuable in terms of TAC, organic acid, fructose and glucose concentrations.

Functional Diversity of Nectary Structure and Nectar Composition in the Genus Fritillaria (Liliaceae)

Fritillaria is a genus consisting of 130 to 140 species of bulbous plants, native to temperate regions of the northern hemisphere. Generally viewed as an insect pollinated genus with the exception of two North American species, Fritillaria gentneri and F. recurva, which are described as hummingbird-pollinated and the Asian species, F. imperialis, described as passerine-pollinated. These pollinator shifts are possibly the result of adaptive changes to the structure and morphology of the nectary, as well as a change in the nectar concentration and composition. A study was conducted in a target group of 56 Fritillaria species, based on the morphology of their nectaries and nectar composition to assess the significance of pollination mode as well as its predisposition for the evolution of bird pollination. All species studied had nectaries located at their tepal base and produced nectar, but their size, shape, color, and composition all varied. Most fritillaries had hexose-rich nectar, in easily accessible and unprotected nectaries. Scanning electron microscope (SEM) analysis revealed that the surface of the nectaries of most Fritillaria species was flat and clearly distinct from that of the surrounding tissues, which might be regarded as an adaptation for insect-pollination. Nectaries of F. imperialis were considerably larger and had dilute nectar without sucrose, which was produced profusely, thereby fulfilling the criteria characteristic of ornithophilous flowers. The copious nectar of presumed hummingbird-pollinated species was rather balanced and of medium sugar concentration. Their large lanceolate nectaries contrasted sharply with the tessellated background of their tepals. These characters might indicate a mixed pollination system that engages both birds and insects. Floral anatomy and microstructure and nectar composition for Fritillaria species in subgenera Korolkowia and Liliorhiza are studied for the first time.