Pollinator

Lipotriches sp. bee pollinating flowers

The most recognized pollinators are the various species of bees,[10] which are plainly adapted to pollination. Bees typically are fuzzy and carry an electrostatic charge. Both features help pollen grains adhere to their bodies, but they also have specialized pollen-carrying structures; in most bees, this takes the form of a structure known as the scopa, which is on the hind legs of most bees, and/or the lower abdomen (e.g., of megachilid bees), made up of thick, plumose setae. Honey bees, bumblebees, and their relatives do not have a scopa, but the hind leg is modified into a structure called the corbicula (also known as the "pollen basket"). Most bees gather nectar, a concentrated energy source, and pollen, which is high protein food, to nurture their young, and transfer some among the flowers as they are working.[11] Euglossine bees pollinate orchids, but these are male bees collecting floral scents rather than females gathering nectar or pollen. Female orchid bees act as pollinators, but of flowers other than orchids. Eusocial bees such as honey bees need an abundant and steady pollen source to multiply.

Honey bee pollinating a plum tree. Bees are the most effective insect pollinators.

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 contracted out as pollinators by beekeepers, 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.

An Australian painted lady feeding on nectar

Lepidoptera (butterflies and moths) may also pollinate to various degrees.[12] They are not major pollinators of food crops, but various moths are important pollinators of other commercial crops such as tobacco. Pollination by certain moths may be important, however, or even crucial, for some wildflowers mutually adapted to specialist pollinators. Spectacular examples include orchids such as Angraecum sesquipedale, dependent on a particular hawk moth, Morgan's sphinx. Yucca species provide other examples, being fertilised in elaborate ecological interactions with particular species of yucca moths.

Many bee flies, and some Tabanidae and Nemestrinidae are particularly adapted to pollinating fynbos and Karoo plants with narrow, deep corolla tubes, such as Lapeirousia species. Part of the adaptation takes the form of remarkably long probosces. This also applies to empidine dance flies (Empidinae) that visit a wide range of flowering plants, some species of which can pollinate the woodland geranium (Geranium sylvaticum L.) as effectively as bees.[13]

Tabanid fly on a thistle flower

Carrion flies and flesh flies in families such as Calliphoridae and Sarcophagidae are important for some species of plants whose flowers exude a fetid odor. 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.

Hoverflies are important pollinators of flowering plants worldwide.[14] Often hoverflies are considered to be the second most important pollinators after wild bees.[14] 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.[15] Another plant, the slipper orchid in southwest China, also achieves pollination by deceit by exploiting the innate yellow colour preference of syrphids.[16]

Some male dacine fruit flies 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.[17][18][19]

A Scoliid wasp (Scolia chrysotricha) foraging

Many insects other than bees accomplish pollination by visiting flowers for nectar or pollen, or commonly both. Many do so adventitiously, but the most important pollinators are specialists for at least parts of their life cycles for at least certain functions.

Prominent among Hymenoptera other than bees are predatory aculeate wasps (especially Crabronidae, Sphecidae, Vespidae, and Pompilidae). The term "pollen wasps", in particular, is widely applied to the Masarinae, a subfamily of the Vespidae; they are remarkable among solitary wasps 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.

Some Diptera (flies) may be the main pollinators at higher elevations of mountains,[20][21] whereas bumblebee species are typically the only other pollinators in alpine regions at timberline and beyond.

Some adult mosquitoes, 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.[22][23]

Beetles 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.

Minute midges and flower-thrips can occur in vast numbers, moving between flowers and plant individuals, enabling some species to contribute to the pollination of tree-crops such as cacao, Theobroma cacao[24] L. (Malvaceae) and elderflower Sambucus nigra L. (Adoxaceae).[25] Ants 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 bees or wasps to attempt to mate with them, conveying pollinia in the process. Examples are known from all continents apart from Antarctica, though Australia appears to be exceptionally rich in examples.[26]

Whole groups of plants, such as certain fynbos Moraea and Erica species produce flowers on sticky peduncles or with sticky corolla tubes that only permit access to flying pollinators, whether bird, bat, or insect.

Experimental evidence has shown invertebrates (mostly small crustaceans[9]) acting as pollinators in underwater environments. Beds of seagrass have been shown to reproduce this way in the absence of currents. It is not yet known how important invertebrate pollinators might be for other species.[8][27] Later, Idotea balthica was discovered to help Gracilaria gracilis reproduce – the first known case of an animal helping algae reproduce.[28][29]

Tropical flowers like Tacca chantrieri are bat-pollinated.

Green violetear with pollen on bill, Curi Cancha Wildlife Refuge, Costa Rica

Bats are important pollinators of some tropical flowers, visiting to take nectar.[30] Birds, particularly hummingbirds, honeyeaters and sunbirds also accomplish much pollination, especially of deep-throated flowers. Other vertebrates, such as kinkajous, monkeys, lemurs, possums, rodents and lizards[31][32] have been recorded pollinating some plants.

Humans can be pollinators, as many gardeners have discovered that they must hand pollinate garden vegetables, whether because of pollinator decline (as has been occurring in parts of the U.S. since the mid-20th century) 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 pores. This can be done by wind, by humans, or by a sonicating 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.

Neonicotinoids (Neonics) are a class of synthetic insecticides that are the most widely applied pesticides today due to its water solubility and ability to treat a wide variety of pests. Neonics are highly environmentally persistent, and may contaminate terrestrial and aquatic habitats for as much as six years. Exposed honeybees' (Apis mellifera) have been seen to have lower reproductive output, reduction in nest building or failed to build nests, reduced foraging abilities, and weakened immunity.[40]

Researchers are still trying to determine how to scientifically best restore and maintain the diverse pollinator habitats found around the world. Many studies conclude that restoration and conservation are key to maintaining biodiversity and pollinator populations. According to the Kansas National Park Service, native tallgrass prairie was widespread through North America and home to over 300 species of flowering plants. This habitat is crucial to wild pollinators and now only covers 4% of its original 170-million acre range.[41] By restoring wild pollinators natural habitat and maintaining Earth's biodiversity, populations are assumed to increase.

In recent times, environmental groups have put pressure on the Environmental Protection Agency to ban neonicotinoids, a type of insecticide. In May 2015, the Obama administration released a strategy called National Strategy to Promote the Health of Honey Bees and Other Pollinators. The administration announced it would include input from the pesticide industry in putting together the initiative.[42]

The task force goal is "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."[43]

The EPA and U.S. Department of Agriculture are leading the task force.[42]

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 NAPCC and federal government agencies, responsible for more than 1.5 billion acres of land protections and management.[44]

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.[45]

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.[46]

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.[47]