Pollination - An Introduction
Transferring pollen grains from a flower's male anther to its female stigma is the process of pollination. Every living thing, including plants, strives to produce progeny for the following generation. Plants create their seeds using flowers as their tools. Only when pollen is exchanged between flowers of the same species seeds can be produced. A community of individuals that are capable of freely interbreeding with one another but do not do so due to geographic, reproductive, or other restrictions is referred to as a species.
Pollination By Animals - Zoophily
The reproduction of flowering plants and the production of most fruits and vegetables both depend heavily on animal pollinators. Pollinators are necessary for major plants to develop seeds and fruit. Over three-quarters of the plants that produce the basic crops that feed humanity and about 80% of all flowering plants rely on animal pollinators. Both plants and animals are mutually benefited from pollination of animals. It is also known as Zoophily. Typically, most blooming plants are pollinated by invertebrates. However, vertebrates like birds and bats also work well as pollination facilitators.
Plants that depend on animals to pollinate have specific adaptations that attract pollinators. These include:
Brightly coloured flowers
Sweet nectars
Appealing patterns and shapes
Examples of Animals that help in pollination are Bees, beetles, butterflies, Ants, Hummingbirds, bats, rodents, lemurs, lizards, wasps, moths, and slugs.
Diversity of Animal Pollination
The degree to which pollination mutualisms specialise or generalise also varies. Interactions in which each partner is required to be involved are at one extreme. The two traditional examples are yuccas and yucca moths, as well as figs and fig wasps. In the latter interaction, moths from the genera Tegeticula and Parategeticula (Prodoxidae) oviposit into and pollinate Yucca species flowers (Asparagaceae).
However, some of the seeds are consumed by developing moth larvae before they fall to the soil beneath the plant, enter diapause as pupae, wait for the recurrence of favourable conditions, emerge as adults, and resume the cycle. The moths are both pollinators and seed predators, which contributes to broad pollination; in fact, this antagonistic aspect of the association may help to explain its high degree of reciprocal specificity. Additionally, certain other highly specific systems, such as figs and their wasps, have mutualistic and hostile relationships.
On the other end of the spectrum are plants that are extremely generalised and draw a variety of insects and other animals as pollinators, as well as pollinators that employ a wide variety of flowers. Numerous species of the sunflower and carrot families (Asteraceae and Apiaceae) represent the former, whereas many bumblebee species, many hummingbird species, and bees of the genus Apis (including the honeybee Apis mellifera) represent the latter.
Importance of Animal Pollination
Animal pollination assists abiotic agents like the wind in pollinating some plant species. Animal pollination is frequently the only method of sexual reproduction. On the other hand, many pollinators are forced to eat nectar for their body metabolism, which relies on pollen as a protein supply. But Animals permit more directed pollen migration among plants in comparison to abiotic pollen carriers. Because of its crucial significance in the reproduction of individual plants, animal pollination serves an equally important role at the level of all ecosystems, both natural and managed.
Many plant species' persistence, recruitment of seedlings, and seed crops would be in danger without pollination. Unfortunately, a variety of anthropogenic factors, such as habitat loss, pesticide usage, and the introduction of alien species, can have a negative impact on pollinators. For instance, certain species of bumblebees in North America are rapidly declining, probably because of parasite infections brought in by humans.
Along with other grievances against plant populations (such as inbreeding depression in small populations), these dangers to pollinators could lead to the local or global extinction of species. As a free and indispensable ecosystem function, pollination has been valued economically by ecologists and economists.
Pollination By Mammals
Animals other than bees also transport pollen from one blossom to another. Additionally, pollinators include animals with backbones like lizards, birds, mice, and bats. Vertebrate pollinators are more likely to have co-evolved close connections of high value to the plants they serve, providing vital reproductive aid for which few or no other species may substitute while being less familiar as flower visitors than insect pollinators.
Around 528 plant species are pollinated by bats worldwide, including the "King of Fruits" of Southeast Asia, durian, African locust beans, and dragon fruit. Numerous bat species have coevolved close ties of reliance with the plants they eat in exchange for the transportation of pollen. Among these, the greater (Leptonycteris nivalis) and smaller (Leptonycteris yerbabuenae) long-nosed bats are fully responsible for the blue agave (Agave tequilana), the source of tequila.
Only at night do the cacti release their long, narrow blossoms, attracting bats with the scent of spoiled fruit. Long-nosed bats travel from Central America to southern New Mexico, Arizona, and Sonora each summer, where they perform important pollination work for the saguaro (Cereus giganteus), the tall, recognisable cactus of the American Southwest. For the bat to be able to migrate, flowering and fruiting must occur at precisely the right times.
Interesting Facts
More than 20,000 species of wild bees in the world contribute to pollination.
Pollinators can increase crop yield by 24% in small, diverse farms.
Bees have four wings: they hook two wings on each side to form one large wing for flying and unhook them when they are not.
One pound of white clover honey represents about 17,330 foraging trips by honeybees to about 8.7 million flowers. That is 7,221 hrs of bee labour.
Key Features
Both invertebrates and vertebrates play a crucial role in pollination
Animals, insects, and butterflies are biotic agents of pollination.
Entomophily refers to pollination by insects, while ornithophily refers to pollination by birds. Zoophily is the term for pollination by vertebrates.
Some species of bats (notably the leaf-nosed bats) can transport pollen up to 17km between plants.
FAQs on Pollination By Animals
1. What is pollination by animals called?
Pollination by animals is broadly known as zoophily. This biological process involves the transfer of pollen from the male anther of a flower to the female stigma by any animal. Specific terms are used for different types of animal pollinators, such as entomophily for insects and ornithophily for birds.
2. What is the basic process of animal pollination?
The process of animal pollination occurs when an animal, attracted by a flower's features, visits it to feed on nectar or pollen. During this visit, pollen grains from the anther adhere to the animal's body (like its fur, feathers, or scales). When the animal moves to another flower of the same species, it transfers these pollen grains to the stigma, facilitating fertilisation and subsequent seed production.
3. What are some common examples of animal pollinators?
A wide variety of animals act as pollinators. The most common examples include:
- Insects: Bees, butterflies, moths, wasps, beetles, and ants.
- Birds: Hummingbirds, sunbirds, and honeyeaters.
- Mammals: Bats, rodents, and even some primates like lemurs.
- Other animals: In some unique cases, reptiles like lizards can also be pollinators.
4. How do plants and animals benefit from zoophily in a mutualistic relationship?
Zoophily is a classic example of mutualism, where both the plant and the animal benefit. The plant achieves successful reproduction by having its pollen efficiently transferred to another flower, ensuring genetic diversity and seed production. In return, the animal receives a reward, typically in the form of high-energy food like nectar or protein-rich pollen. This co-dependent relationship drives the evolution of both species.
5. What special features do flowers develop to attract different animal pollinators?
Flowers evolve specific adaptations or 'pollination syndromes' to attract their target pollinators. Key features include:
- Bright Colours: Bee-pollinated flowers are often blue or yellow, while bird-pollinated flowers are typically red or orange.
- Strong Scents: Flowers pollinated by moths or bats, which are active at night, often have strong, sweet, or fruity scents.
- Nectar Guides: Many flowers have patterns, visible in ultraviolet light to insects, that act as guides pointing towards the nectar.
- Flower Shape: The shape of a flower often corresponds to the pollinator's mouthparts, like long tubular flowers for hummingbirds or broad, flat flowers that act as a landing pad for beetles and flies.
6. What is the difference between pollination by insects (entomophily) and pollination by birds (ornithophily)?
The key difference lies in the adaptations of the flowers. Entomophilous (insect-pollinated) flowers are often fragrant, have nectar guides, and provide a landing platform. In contrast, ornithophilous (bird-pollinated) flowers are typically large, tubular, brightly coloured in shades of red or orange, and produce large amounts of dilute nectar. They are usually odourless because birds have a poor sense of smell.
7. Why is animal pollination considered more efficient than pollination by abiotic agents like wind?
Animal pollination is considered more efficient because it is a targeted and directed process. Animals move from one flower to another of the same species, ensuring that pollen is delivered precisely where it is needed. This significantly reduces pollen wastage. Wind pollination, on the other hand, is random and non-directional, requiring plants to produce enormous quantities of lightweight pollen with a very low probability of it landing on the correct stigma.
8. Which important crops rely on animal pollination for their production?
Many of the world's most important agricultural crops depend on animal pollinators. Animal pollination is crucial for the production of most fruits, vegetables, nuts, and seeds. Key examples include apples, almonds, blueberries, squash, strawberries, chocolate (from the cacao tree), and coffee. The economic value of these pollinators to global agriculture is estimated to be billions of dollars annually.
9. What are some less common or surprising animal pollinators beyond bees and butterflies?
While insects are the most famous pollinators, many other animals play this vital role. Some surprising examples include bats, which are crucial for pollinating agave (the source of tequila) and many cacti. Some species of rodents, possums, and lemurs also act as pollinators, attracted to nectar-rich flowers. Even certain lizards and geckos have been observed pollinating flowers on islands where insect populations might be low.
10. How does the relationship between the yucca moth and the yucca plant represent a highly specialised form of pollination?
The relationship between the yucca moth and the yucca plant is a prime example of obligate mutualism, where neither species can reproduce without the other. The female yucca moth collects pollen and deliberately packs it onto the stigma of a yucca flower, ensuring pollination. She then lays her eggs in the flower's ovary. As the seeds develop, the moth larvae feed on a portion of them. This system is highly specialised because the plant sacrifices some seeds to guarantee successful pollination by its only effective pollinator.
