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A pollinator is an animal that moves pollen from the male anther of a flower to the female carpel of a flower. This helps to bring about fertilization of the in the flower by the male gametes from the pollen grains.
Insects are the major pollinators of most plants, and insect pollinators include all families of bees and most families of Aculeata; ; many families of flies; many (both butterflies and moths); and many families of beetles. Vertebrates, mainly bats and birds, but also some non-bat mammals (, , Phalangeriformes, ) and some pollinate certain plants. Among the pollinating birds are , honeyeaters and sunbirds with long beaks; they pollinate a number of deep-throated flowers. Humans may also carry out artificial pollination.
A pollinator is different from a pollenizer, a plant that is a source of pollen for the pollination process.
Although non-bee pollinators have been seen to be less effective at depositing pollen than bee pollinators one study showed that non-bees made more visits than bees resulting in non-bees performing 38% of visits to crop flowers, outweighing the ineffectiveness of their ability to pollinate.
It has recently been discovered that , which are not , are also pollinated by insects. In 2016, researchers showed evidence of pollination occurring underwater, which was previously thought not to happen.
Honey bees travel from flower to flower, collecting nectar (later converted to honey), and pollen grains. The bee collects the pollen by rubbing against the anthers. The pollen collects on the hind legs, in a structure referred to as a "pollen basket". As the bee flies from flower to flower, some of the pollen grains are transferred onto the stigma of other flowers. Nectar provides the energy for bee nutrition; pollen provides the protein. When bees are rearing large quantities of brood (beekeepers say hives are "building"), bees deliberately gather pollen to meet the nutritional needs of the brood.
Good pollination management seeks to have bees in a "building" state during the bloom period of the crop, thus requiring them to gather pollen, and making them more efficient pollinators. Thus, the management techniques of a beekeeper providing pollination services are different from, and to some extent in tension with, those of a beekeeper who is trying to produce honey. Millions of hives of honey bees are out as pollinators by beekeeping, and honey bees are by far the most important commercial pollinating agents, but many other kinds of pollinators, from blue bottle flies, to bumblebees, orchard mason bees, and leaf cutter bees are cultured and sold for managed pollination.
Other species of bees differ in various details of their behavior and pollen-gathering habits, and honey bees are not native to the Western Hemisphere; all pollination of native plants in the Americas and Australia historically has been performed by various native bees. It has also been found that non-native plants may have positive effects on native bee pollinators while also influencing their foraging patterns and bee–plant networks.
Carrion flies and flesh flies in families such as Calliphoridae and Flesh-fly are important for some species of plants whose flowers Carrion flower. The plants' ecological strategy varies; several species of Stapelia, for example, attract carrion flies that futilely lay their eggs on the flower, where their larvae promptly starve for lack of carrion. Other species do decay rapidly after ripening, and offer the visiting insects large masses of food, as well as pollen and sometimes seed to carry off when they leave.
Hoverfly are important pollinators of flowering plants worldwide. Often hoverflies are considered to be the second most important pollinators after wild bees. Although hoverflies as a whole are generally considered to be nonselective pollinators, some species have more specialized relationships. The orchid species Epipactis veratrifolia mimics alarm pheromones of aphids to attract hover flies for pollination. Another plant, the slipper orchid in southwest China, also achieves pollination by deceit by exploiting the innate yellow colour preference of syrphids.
Some male Dacini are exclusive pollinators of some wild Bulbophyllum orchids that lack nectar and have a specific chemical attractant and reward (methyl eugenol, raspberry ketone or zingerone) present in their floral fragrances.
Some flies, especially Anthomyiidae, Empididae and Muscidae, may be the main pollinators at higher elevations of mountains, whereas bumblebee species are typically the only other pollinators in alpine regions at timberline and beyond.
Some adult , if they feed on nectar, may act as pollinators; Aedes communis, a species found in North America, is known to pollinate Platanthera obtusata, commonly referred as the blunt-leaved orchid.
Biting midges (Ceratopogonidae) pollinate Theobroma cacao (Malvaceae), whose flowers have pollen inaccessible to larger pollinators.
Prominent among Hymenoptera other than bees are wasps, especially Crabronidae, Cuckoo wasp, Ichneumonidae, Sphecidae and Vespidae. Some wasps are comparable to or even superior to some bees as pollinators. The term "", in particular, is widely applied to the Masarinae, a Taxonomic rank of the Vespidae; they are remarkable among hunting wasp in that they specialise in gathering pollen for feeding their larvae, carried internally and regurgitated into a mud chamber prior to oviposition. Also, males of many species of bees and wasps, though they do not gather pollen, rely on flowers as sources of energy (in the form of nectar) and also as territories for meeting fertile females that visit the flowers.
of species that specialise in eating pollen, nectar, or flowers themselves, may be important cross-pollinators of some plants such as members of the Araceae and Zamiaceae, that produce prodigious amounts of pollen. Others, for example the Hopliini, specialise on flowers of Asteraceae and Aizoaceae.
Thrips pollinate plants such as elderflower Sambucus nigra (Adoxaceae) and pointleaf manzanita, Arctostaphylos pungens (Ericaceae). also pollinate some kinds of flowers, but for the most part they are parasites, consuming nectar and/or pollen without conveying useful amounts of pollen to a stigma. Other insect orders are rarely pollinators, and then typically only incidentally (e.g., Hemiptera such as Anthocoridae and Miridae).
A strategy of great biological interest is that of sexual deception, where plants, generally orchids, produce remarkably complex combinations of pheromonal attractants and physical mimicry that induce male Apidae or Tiphiidae to attempt to mate with them, conveying Pollinium in the process. Examples are known from all continents apart from Antarctica, though Australia appears to be exceptionally rich in examples.
Whole groups of plants, such as certain fynbos Moraea and Erica species produce flowers on sticky peduncles or with sticky Petal tubes that only permit access to flying pollinators, whether bird, bat, or insect.
Humans can be pollinators, as many have discovered that they must hand pollination garden , whether because of pollinator decline or simply to keep a strain genetically pure. This can involve using a small brush or cotton swab to move pollen, or to simply tap or shake tomato blossoms to release the pollen for the self-pollinating flowers. Tomato blossoms are self-fertile, but (with the exception of potato-leaf varieties) have the pollen inside the anther, and the flower requires shaking to release the pollen through . This can be done by wind, by humans, or by a Buzz pollination bee (one that vibrates its wing muscles while perched on the flower), such as a bumblebee. Sonicating bees are extremely efficient pollinators of tomatoes, and colonies of bumblebees are quickly replacing humans as the primary pollinators for greenhouse tomatoes.
/ref> Floral diet diversity has been seen to increase immunocompetence levels in honeybees (Apis mellifera) where diets that consisted of a wide variety of flowering species induced higher glucose oxidase activity, which honeybees' produce to sterilize their colony. More than 30% of global bee species depend on non-floral resources for nest building, protection, health, pest resistance, and alternative food sources. Non-floral resources include leaves, soil, plant resins and secretions, and are often provided by woody-vegetation.
A 2017 report done for the Center of Biological Diversity utilized data documented in the United States on native bee species and found that nearly 1 in 4 (347 species of 1,437 species) is imperiled and at increasing risk of extinction. More than half of the native bee species is in decline and 40% of global insect pollinators (primarily native bees) are highly threatened.
Declines in the health and population of pollinators pose what could be a significant threat to the integrity of biodiversity, to global food webs, and to human health. At least 80% of our world's crop species require pollination to set seed. A 2021 study estimated that without pollinators, fertility would be reduced by 80% in half all wild plant species and one-third of all wild plant species would fail to produce any seeds at all.
An estimated one out of every three bites of food comes to us through the work of animal pollinators. The quality of pollinator service has declined over time and this had led to concerns that pollination will be less resistant to extinction in the future.
A 2022 study concludes that the decline of pollinator populations is responsible for 500,000 early human deaths per year by reducing the supply of healthy foods. A decline of pollinators has caused 3-5% loss of fruits, vegetables and nuts. Lower consumption of these healthy foods translates to 1% of all deaths, according to the authors.
On June 20, 2014, President Barack Obama issued a presidential memorandum entitled "Creating a Federal Strategy to Promote the Health of Honey Bees and Other Pollinators". The President's memorandum established a Pollinator Health Task Force, to be co-chaired by the Secretary of Agriculture and the Administrator of the Environmental Protection Agency. The memorandum stated:
In May 2015, the Pollinator Health Task Force issued a "National Strategy to Promote the Health of Honey Bees and Other Pollinators". The national strategy outlined a comprehensive approach to tackling and reducing the impact of multiple stressors on pollinator health, including pests and pathogens, reduced habitat, lack of nutritional resources, and exposure to pesticides.
The national strategy laid out federal actions to achieve three goals:
Many of the priority projects that the national strategy identified focused on the I-35 corridor, which extends for from Texas to Minnesota. The area through which that highway travels provides spring and summer breeding habitats in the United States' key monarch migration corridor.
The Pollinator Health Task Force simultaneously issued a "Pollinator Research Action Plan". The Plan outlined five main action areas, covered in ten subject-specific chapters. The action areas were: (1) Setting a Baseline; (2) Assessing Environmental Stressors; (3) Restoring Habitat; (4) Understanding and Supporting Stakeholders; (5) Curating and Sharing Knowledge.
In June 2016, the Task Force issued a "Pollinator Partnership Action Plan". That Plan provided examples of past, ongoing, and possible future collaborations between the federal government and non-federal institutions to support pollinator health under each of the national strategy's goals.
The structure of plant-pollinator networks may have large consequences for the way in which pollinator communities respond to increasingly harsh conditions. Mathematical models, examining the consequences of this network structure for the stability of pollinator communities suggest that the specific way in which plant-pollinator networks are organized minimizes competition between pollinators and may even lead to strong indirect facilitation between pollinators when conditions are harsh. This allows pollinator species to survive together under harsh conditions. But it also means that pollinator species collapse simultaneously when conditions pass a critical point. This simultaneous collapse occurs, because pollinator species depend on each other when surviving under difficult conditions.
Such a community-wide collapse, involving many pollinator species, can occur suddenly when increasingly harsh conditions pass a critical point and recovery from such a collapse might not be easy. The improvement in conditions needed for pollinators to recover, could be substantially larger than the improvement needed to return to conditions at which the pollinator community collapsed.
North America
The North American Pollinator Protection Campaign (NAPPC) aims to promote pollinator health across the North America and has organized annual conferences since 1997, creates task forces to implement specific objectives that includes public education and policy research, and is developing strategic plans for conservation that looks to establish partnership between government entities. 11 pollinator-protection agreements have been signed between NAPPC and federal government agencies, responsible for more than 1.5 billion acres of land protections and management.
Europe
Along with the European Green Deal, which contains initiatives that support pollinator populations, the European Union has implemented the EU Biodiversity Strategy for 2030 which includes the EU Pollinators Initiative that sets long-term objectives to reverse pollinator decline in diversity and numbers by 2030. This initiative includes: (1) improving knowledge of pollinator decline, its causes and consequences; (2) tackling the causes of pollinator decline; and (3) raising awareness, engaging society-at-large and promoting collaboration.
South America
The Healthy Hives Latin America 2020 (Salud Apícola 2020 Latinoamérica) program is a collaboration between the Bayer Bee Care Center and the Fraunhofer Chile Research Foundation, that works alongside local researchers at universities and beekeepers' associations. The program focuses on increasing the number of healthy worker bees and their colonies by monitoring honey bee health and the contributing factors. This includes educating beekeepers and research collaborations to jointly work on honey bee health. Founded in 2015 with a preliminary project in Chile, the program has expanded to Colombia, Argentina, and Costa Rica.
Global
The ‘Coalition of the Willing on Pollinators' (Promote Pollinators) was initiated in 2016 during the Convention on Biological Diversity's Conference of the Parties (CBD COP13) and is a growing alliance of countries and observers who support the notion that country-led politics can lead to policy measures and innovative action to protect pollinators'. Their supporters are growing steadily, in which 30 countries currently participate.
Structure of plant-pollinator networks
Wild pollinators often visit many plant species and plants are visited by many pollinator species. All these relations together form a network of interactions between plants and pollinators. Surprising similarities were found in the structure of networks consisting out of the interactions between plants and pollinators. This structure was found to be similar in very different ecosystems on different continents, consisting of entirely different species.
See also
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