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This chapter reviews currently available information on the success of introduced pollinators, their effects on native ecosystems, and examines the viability of using native pollinators to prevent unnecessary introductions of exotic species. Exotic species of bees have been introduced to different countries as crop pollinators. Well-known examples are the alfalfa leafcutting bee (Megachile rotundata) and several species of bumble bees (Bombus spp.). In most cases, these imports have been done without prior assessment of possible negative impacts of the pollinators on native ecosystems. Other species have been accidentally introduced, or introduced for purposes other than pollination of crops. The best known of such introductions is the African honey bee, imported to Brazil in the 1950s. African honey bees (Apis mellifera scutellata) have become important pollinators of crops like coffee or avocado in tropical and subtropical regions of the Americas.

This chapter examines the interactions between exotic invasive plants focusing on the following questions: How do bees contribute to invasive plant establishment and spread? How do resident bee communities respond to the invasion? What are the indirect effects of the invasion mediated by pollinator communities? New data on the frequency of insect pollinator-dependent invasive plant species in US natural areas confirm that pollinator interactions are likely to play a role in the outcome of many invasions. Generalizations are sought regarding which invasive plant–bee interactions likely contribute most to reproduction of invasive plants and negative indirect effects on native plant communities. Finally, mechanisms behind pollinator-mediated indirect effects of invasive plants on native plants are examined by considering invasive plants as resources that contribute to bee population abundance and community structure.

This chapter examines the environmental economics of pollination, with particular emphasis on the costs that may be incurred and that have to be offset against the rewards gathered. Pollination is usually regarded as a mutualism, of benefit to both partners, each of which gains in fitness. In such a relationship, both should be trying to maximize their survival and ultimately their reproductive success, which will require balancing their costs against the rewards and hence assessing the net benefits gained. Disentangling the economic aspects of the interaction for each participant has become a major area of study in pollination ecology. The chapter first considers the conflicting requirements of a plant and its pollinators before discussing the costs incurred by the plant and the costs incurred by a flower-visiting animal. It also explores the effects of the environment on flower-pollinator interactions as economic transactions.

This chapter examines the core issues raised by critiques of pollination syndromes and alternative approaches to characterizing pollination in communities, in the context of floral and pollinator specialization. It first considers theoretical arguments against syndromes and specialization before discussing practical evidence against syndromes, along with proposed alternative approaches, focusing in particular on ecological models of specialization and generalization. It then explores some problems with pollination webs, several key issues relating to specialization and generalization, and selection for specialization in flower–pollinator interactions. It also compares patterns of generalization and specialization in different ecosystems and asks whether generalization can be reversed. The chapter concludes with some reflections on the debate over generalization, specialization, and pollination syndromes.

This chapter focuses on the global pollination crisis. For nearly three decades now there has been evidence of declines in pollinators worldwide, and the problems were explicitly recognized in the United Nations Sao Paulo declaration (1998–1999). However, the ecosystem-level effects of this pollinator decline remain unclear. Therefore long-term data collections are needed to track the changes and to understand their underlying causes with a view to finding sustainable solutions. This chapter examines the needs for assessment of pollinator declines, along with some of the key threats to pollinators and to pollination services including: habitat degradation and destruction; habitat fragmentation; intensive agriculture; increasing prevalence of fires in areas where human impacts are substantial; introduced animal species and pollinators; invasive plant species and changing floras; diseases and other natural threats to key pollinators; and climate change.

It is clear from a merely cursory glance around any garden in the summer months that flowers come in an enormous variety of sizes, shapes, colours, and scents. The book now focusses on the differences between flowers, as opposed to the molecular similarities that unite them. This chapter begins by considering the different ways that flowers can be pollinated. It is a basic premise underlying much of floral biology that differences in pollination system explain many of the differences in floral form. The evidence to support this premise is not as compelling as we might like to think, as discussed in later chapters. However, to set the stage for those discussions, this chapter looks at the historical concept of the pollination syndrome and the predictions it makes about floral morphology. The chapter considers the roles different animal pollinators may play in influencing floral evolution.

This chapter investigates whether the different shapes, structures, and colours that flowers produce have the potential to enhance pollinator visitation. To do this, they must fulfil two criteria. First, they must be visible to the appropriate pollinator, or detectable using some other sense. Secondly, the pollinator must discriminate between different floral forms. Simply because a change in floral form is detectable to an animal, it does not necessarily follow that the animal will discriminate between the original and the novel form. Such discrimination will only occur if one form provides an advantage to the animal. This chapter begins by discussing the current evidence on what different pollinating animals can see and detect in other ways. It then considers the experimental evidence that pollinators do discriminate between different floral forms, focussing on flower colour, flower shape, and flower scent.

The concept of the pollination syndrome has underlain much of floral biology for many years. This chapter assesses the usefulness of the concept in understanding flowers and flowering. It begins by considering why and how the pollination syndrome concept has become so entrenched in the literature on flowering, and then examines whether the key assumptions that underlie it are met. Finally, it assesses the experimental evidence that pollination syndromes do exist, and the experimental evidence which shows them to be false — those cases where the major pollinator in the native habitat is not that which the flower's morphology would lead you to predict. The chapter also provides a brief overview of the relative importance of generalization and specialization in pollination ecology.

This chapter describes the need for pollination in greenhouses due to its special agro-ecological conditions and unique constraints. The advantages that greenhouses hold for both achieving pollination of particular crops and for safeguarding managed pollinators are compared with open air cultures. The traits of the two main greenhouse pollinators — bumble bees and honey bees — are discussed according to their relevance for pollination in this horticultural system. Finally, some examples of pollination of greenhouse cultures and predictions for the future development of pollination in greenhouses are described.

Federal land managers desire seed of Great Basin perennial wildflowers, mixed with grass and shrub seed, for restoration of millions of acres of sagebrush communities degraded by altered wildfire regimes and exotic grasses and forbs. For fifteen candidate wildflower species to be farmed for seed production, all were found to need pollinators, typically bees (Apiformes), for fruit and seed production. Some can be pollinated with currently managed bees (honey bees, alfalfa leafcutting bees), but for others, management protocols and starting populations are being developed for suitable species of native Osmia bees.

Pollinator Biocontrol Vector Technology is a novel application strategy using bees for the delivery of microbial control agents. This technology has been demonstrated for the control of seed set in weeds, suppression of plant diseases and control of insect pests. For this multi-disciplinary approach to be successful, many factors must be considered such as efficacy against the target pests, vector safety, formulation of the inoculum, inoculum dispenser design, and environmental and human safety. Pollinator Biocontrol Vector Technology is a new, reduced risk pest management tool that reduces pesticide use and improves crop pollination resulting in increased yield and crop quality.

This chapter examines pollination syndromes, floral constancy, and pollinator effectiveness. Flowers show enormous adaptive radiation, but the same kind of flower reappears by convergent evolution in many different families. Thus many families produce rather similar, simple bowl-shaped flowers like buttercups; many produce similar zygomorphic tubular lipped flowers; and many produce fluffy flower heads of massed (often white) florets. These broad flower types are the basis of the idea of pollination syndromes—the flowers have converged on certain morphologies and reward patterns because they are exploiting the abilities and preferences of particular kinds of visitor. After providing an overview of pollination syndromes, the chapter explains why pollination syndromes can be defended. It then considers flower constancy, along with the distinction between flower visitors and effective pollinators. It concludes with some observations on how flower visitors can contribute to speciation of plants through specialization and through their constancy.

This chapter examines competition in the context of pollination ecology. Competition is typically treated from the perspective of the plants, but it is also likely to occur among and between the pollinators. Furthermore, competition can occur at various levels—as a structuring factor in communities, as a selective force on an individual plant’s phenology, morphology, or rewards, and at a genetic level structuring competition for pollens between males, and female choice between possible mates. The chapter first considers several types of of competition in pollination ecology, potential outcomes of competition, and competition between pollinators before discussing how selection reduces intraspecific competition among plants and competition among pollinators. It also explores paternity, maternity, and gene flow in coflowering communities, focusing in particular on male competition and female choice, along with gene flow via pollen dispersal and seed dispersal.

This chapter examines how flowers cheat visitors and other flowers. Pollination is not an altruistic exercise; there is a conflict of needs that makes both plants and pollinators liable to cheat to their own benefit. Deception is very common in pollination biology. For a plant, this essentially means getting pollinated and hence fertilized without giving up any reward or resources. This can commonly be achieved by resembling a rewarding species. For a visiting animal, cheating involves extracting nectar or pollen in ways that do not carry any pollen to another flower. The chapter discusses mimicry in flowers and aids to mimicry, including pseudoflowers, pseudonectar, and pseudopollen and pseudoanthers. It also looks at empty flowers as mimics and cheats before concluding with an analysis of mimicry of objects other than flowers, such as reproductive mimicry of brood sites and potential mates (pseudocopulation).

This chapter explores the effects of pollination on herbivory and vice versa. When herbivores and pollinators are both active on plants, there is much scope for differential selection on plant traits, and pollinator-mediated selection can sometimes be overwhelmed by opposing selective forces operating due to herbivory. This can result in increased genetic variation and a compromise phenotype and could potentially promote generalization in the flowers. The chapter examines the balance between these potentially conflicting selective influences on a flowering plant, from both florivores and more general herbivores, and some ways in which the conflicts can be resolved. It first considers the effects of florivory on pollinators and the effects of herbivory on flowering and pollination before discussing defenses against florivory and herbivory affecting flowers.

This chapter examines brood site mutualisms, where the pollinators are florivores. In brood site mutualisms, the pollinators are sometimes referred to as nursery pollinators. Here pollination success affects not only plant fitness but also pollinator fitness, and the balance between costs and benefits may be highly variable from place to place and across seasons. There are at least thirteen known nursery pollination systems, and this phenomenon can be divided into three categories. Two of these are relatively unspecialized, where beetle or lepidopteran larvae develop in decomposing flower heads, or where thrips feed in flowers as pollen parasites. The third category is termed “active pollination,” also known as “seed-eating pollination syndrome.” The chapter first considers nursery pollination and thrips as pollen parasites before discussing active pollination, where active pollen transfer occurs and a clear mutualism results.

This chapter examines pollination that occurs in different kinds of ecosystems and habitats, along with the implications for plant–pollinator interactions. It begins with a discussion of pollination in deserts and semiarid systems, taking into account habitat characteristics, flora and pollinating fauna, problems with triggering and timing of flowering, problems of highly dispersed flowers, increased reproductive allocation in plants, and issues of energetics, heat overload, and water balance for desert plants and animals. The chapter proceeds by considering pollination in Mediterranean ecosystems, humid tropics, and at high latitude and high altitude. Finally, it describes pollination on islands such as the Galapagos Islands, New Zealand, Hawaii, Madagascar, and Faroe Islands.

This chapter focuses on the pollination of crops. Animal pollination is important to the large majority of important crops, including those directly eaten by humans. However, there are differing absolute and relative needs for pollination. The chapter begins with a discussion of food crop types that need animal pollination, including wheat, oats, rice, maize, rye, barley, peanut, potato, cassava, sugarcane, and banana. It then considers a fairly standard set of tests that should be applied to determine what a good pollinator will be. It also provides examples that illustrate particular problems of crop productivity or crop management, from plants grown intensively or on a small and local scale, and in a wide range of habitats. Finally, it examines general approaches to encouraging pollination, along with problems associated with hybrid crops, seed crops, and crop breeding.

This chapter introduces some of the book’s central themes on animal pollination, beginning with a discussion of animals that visit flowers. At least 130,000 species of animals, and probably up to 300,000, are regular flower visitors and potential pollinators. At least 25,000 species of bees are included in this total, all of them obligate flower visitors and often the most important pollinators in a given habitat. There are currently about 260,000 species of angiosperms and it has been traditional to link particular kinds of flowers to particular groups of pollinators. The chapter proceeds by explaining why animals visit flowers, how flowers encourage animal visitors, and what makes a visitor a good pollinator. It also considers the costs, benefits, and conflicts in animal pollination before concluding with an enumeration of reasons why pollination is worth studying.