Pollinators, specialization

Bees, especially orchard mason bees, which are useful fruit tree pollinators, will colonize holes drilled in blocks of wood or paper drinking-straws stacked in a waterproof box, or you can buy special bee boxes. Mason bees emerge early, so the boxes need to be erected in early spring before the apple buds burst. 

Johnson, S.D. and Steiner, K.E. (2000). Generalization versus specialization in plant pollination systems. Trends in Ecology and Evolution 15 140-143. 

Schemske, D. W. and Horvitz, . C. (1984). Variation among floral visitors in pollination ability a precondition for mutualism specialization. Science 225 519-521.

Figure 22.1 Examples from two conceptual axes of interactions between flowers and their animal visitors. Axis 1 is a specialization-generalization spectrum of plant-pollinator interactions. Panel A depicts a guild of red Chilean flowers that share one species of hummingbird as a pollinator. In Panel D, a Perideridia umbel is visited by several families of bees, wasps and flies most are effective pollinators. Axis 2 describes relationships in which animals visit flowers for their own reproductive purposes. In panel B, a female Tegiticula moth gathers pollen from anthers of Yucca filamentosa, for which it is both obligate pollinator and seed predator. In panel C, a Drosophila fly (black arrow) is lured by appearance and smell of decaying matter to a deceptive Aristolochia flower, seen in cross-section. Floral scent plays diverse roles along these axes, including pollinator attraction in food- and sex-based mimicry. All photographs were taken by the author.

Most of a plant s photosynthesis occurs in the leaves. Energy-producing leaves tend to be large, thin, and arranged so that they can all get some sunlight. Leaves may also be adapted for specialized purposes, such as defense, prevention of water loss, and attraction of pollinators or prey. 

Fig-fig wasp interactions are an example of highly specialized and diversified mutualism. Approximately 900 species of Ficus (Moraceae), when receptive, release floral scents that attract specific wasps (Agaonidae) for pollination. The chemical compositions of the floral scents differ considerably among different Ficus species, and several volatiles such as ( )-/3-ocimene, ct-pinene, linalool, trcrns-linalool oxide furanoside (21), 1,8-cineol, f-carvoph vllcnc, germacrene D, a-copaene, and benzyl alcohol have been identified as the dominant components of these scents.89 Such differences in composition of the floral scents of figs induce species specificity in the attraction of fig wasps.90 In addition, in fig flowers, the scent composition differs between the receptive and... 

Males of neotropical euglossine bees (Apidae), called orchid bees, collect odoriferous substances from flowers of orchids and other plants. The floral scents of these species display relatively simple chemical compositions dominated by one or two major components, mostly terpenoids and aromatic compounds such as cr-pinene, 1,8-cineol, eugenol, -dimethoxybenzene (35), 2,3-epoxygeranyl acetate (36), nerolidol, 4-methoxycinnamaldehyde (37), and benzyl benzoate.113 Since the orchid bees have odor preferences, their collection of fragrances leads to specialized pollination of particular plant species. Male bees absorb the floral volatiles with their tarsal hairs, form species-specific bouquets, and finally accumulate them in their hind tibial pouches. These bouquets have potential roles in courtship displays and marking territories.114 115... 

Species of orchids can have very unusual morphological traits and ecological relationships, especially with their species of pollinating insects. For these reasons, along with the great beauty of their flowers, orchids hold a special place in the hearts of botanists, ecologists, and horticulturists. However, appreciation of the intrinsic value of orchids extends far beyond the scientists who work with these plants—few people fail to be enthralled by the loveliness of orchid flowers. 

Floral scents are often complex blends of several compounds. These are mainly fatty-acid derivatives, benzenoids, phenylpropanoids, isoprenoids, nitrogen-and sulfur-containing compounds. Knudsen et al. s (1993) comprehensive review of floral odors reported floral scents with as few as three compounds and as many as several hundred. A study of moth-pollinated flowers from the Nyctaginaceae reported as many as 77 compounds in floral scent and as few as one. Studies that have focussed on identifying the site of volatile production in flowers report that they are produced mostly in the petals. Volatiles are both synthesized and released by the epidermal cells or by special glandular trichomes on the petal surface. Other studies have shown that the odor of pollen is also part of the odor signal. ... 

Since this period and especially over the past 15 years, legislation on the placing of chemical plant protection products on the market has been continuously developing to cope with European regulations. Directive No. 91/414/CEE of July 15 1991 [4], later transcribed into French law, defines the guidelines of the market approval procedure for chemical plant protection products. The provisions related to the effect on the environment and on beneficial organisms, in particular bees and other pollinators came to special importance. 

Plants, year by year, specialized in attract more efficient pollinators and make transportation of their reproductive cells, and therewith could be benefited with cross pollination. The disposition of flowers is an important factor that can be isolated in the branches or grouped in the same floral axis forming inflorescence, colour, odour, size, nectar, oil, pollen and... 

The contribution of Gerhard Prenner (Chapter 11) studies a special case of high stamen and carpel numbers in Acacia celastrifolia and how this appears to be a concerted increase, linked with specific pollination strategies. 

Flexibility of pollination system transitions has been studied in numerous groups of angiosperms. Some conspicuous examples are be mentioned here. Among Phyllanthaceae, in Phyllantheae, specialization to pollination by Epicephala moths evolved at least five times, involving more than 500 Phyllantheae species in this obligate association (Kawakita and Kato, 2009). 

P., Dudash, M. R. and Thomson, J. D. (2004). Pollination syndromes and floral specialization. Annual Review of Ecology, Evolution, and Systematics, 35,375-403. 

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