Recent advances in plant-herbivore interactions
Some aspects of herbivore-plant relationships on Caribbean reefs and seagrass beds. Article (PDF Available) in Aquatic Botany – These studies combined with direct food preference tests indicate that some plants or parts of plants are avoided by herbivores. The possibilities of chemical or. The co-evolutionary struggle between arthropod herbivores and plants to consume or Like all research concerned with inter-species relationships, numerous.
Smaller hairs known as trichomes may cover leaves or stems and are especially effective against invertebrate herbivores. Also the incorporation of silica into cell walls is analogous to that of the role of lignin in that it is a compression-resistant structural component of cell walls; so that plants with their cell walls impregnated with silica are thereby afforded a measure of protection against herbivory.
There are a wide variety of these in nature and a single plant can have hundreds of different chemical defenses. Chemical defenses can be divided into two main groups, carbon-based defenses and nitrogen-based defenses. Terpenes are derived from 5-carbon isoprene units and comprise essential oils, carotenoids, resins, and latex.
They can have a number of functions that disrupt herbivores such as inhibiting adenosine triphosphate ATP formation, molting hormonesor the nervous system.
There are a number of different phenolics such as lignins, which are found in cell walls and are very indigestible except for specialized microorganisms; tanninswhich have a bitter taste and bind to proteins making them indigestible; and furanocumerins, which produce free radicals disrupting DNA, protein, and lipids, and can cause skin irritation.
Nitrogen-based defenses are synthesized from amino acids and primarily come in the form of alkaloids and cyanogens. Alkaloids include commonly recognized substances such as caffeinenicotineand morphine.
Cyanogens get their name from the cyanide stored within their tissues. This is released when the plant is damaged and inhibits cellular respiration and electron transport.
Herbivore adaptations to plant defense - Wikipedia
This suggests that the population of the herbivore fluctuates around the carrying capacity of the food source, in this case the plant. Several factors play into these fluctuating populations and help stabilize predator—prey dynamics. For example, spatial heterogeneity is maintained, which means there will always be pockets of plants not found by herbivores.
This stabilizing dynamic plays an especially important role for specialist herbivores that feed on one species of plant and prevents these specialists from wiping out their food source.
- Herbivore adaptations to plant defense
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- Recent advances in plant-herbivore interactions
Keystone herbivores keep vegetation populations in check and allow for a greater diversity of both herbivores and plants. This beneficial herbivory takes the form of mutualisms in which both partners benefit in some way from the interaction. Seed dispersal by herbivores and pollination are two forms of mutualistic herbivory in which the herbivore receives a food resource and the plant is aided in reproduction. Since algae and seaweeds grow much faster than corals they can occupy spaces where corals could have settled.
They can outgrow and thus outcompete corals on bare surfaces. In the absence of plant-eating fish, seaweeds deprive corals of sunlight. Current research, however, is revealing that herbivory has some potential benefits to plants.
One example is canopy grazing by insects, which allows more light to penetrate into the lower layers of the forest. Gypsy moth grazing on canopy trees in some areas of Virginia's Blue Ridge Mountains, for instance, has resulted in more light penetration and therefore a more diverse and productive ground layer.
Herbivores and Their Food Plants Bison, sheep, and other grazers - Succulent forbs, grasses, grass-like plants Deer and other ungulate browsers - Leaves and twigs of woody plants such as willows, arborvitaes, yews Beaver - Tree bark, young shoots, leaves Rodents - Succulent forbs, grasses, grass-like plants Rabbits - Succulent forbs, grasses, bark Voles - Roots, bark Caterpillars - Leaves; in some cases, of specific species Monarch butterfly - Milkweeds Gypsy moth - Oaks and other hardwoods Aphids - Plant juices; in some cases, of specific species Many birds - Seeds and fruits Locusts - All plants; seeds, leaves, and stems Plants and Their Pollinators Pollination is the transfer of the pollen from one flower to the stigma, or female reproductive organ, of another, which results in fertilization and, ultimately, the formation of seeds.
The earliest plants were pollinated by wind, and for some modern plants this is still the most expedient method.
Plant Interactions with Arthropod Herbivores: State of the Field
Many trees, all grasses, and plants with inconspicuous flowers are designed for wind pollination. Bright, showy flowers evolved for another purpose—to attract a pollinator. Many plants depend on animals for pollination. Insects, birds, even bats are important for perpetuating plants. The flowers of these plants evolved in concert with their pollinators, and their form reflects the form and habits of their pollinators.
Bee-pollinated plants are often irregular in shape, with a lip that acts as a landing pad to facilitate the bee's entry into the flower. Butterfly-pollinated flowers are often broad and flat, like helicopter pads.
The flowers of many plants are brightly colored to attract their insect pollinators, and many offer nectar as an enticement. Hummingbirds, with their long beaks, pollinate tubular flowers.
Bats require open flowers with room for their wings, such as those of the saguaro cactus. In the tropics, birds and bats take the place of insects as pollinators. Hummingbirds and honeycreepers, for example, have distinctive beaks that have evolved to exploit flowers.
Often, a beak may be so specialized that it is only effective on a small group of flowers. The pollinators, in turn, have evolved to take advantage of the flowers. A successful pollinator typically has good color vision, a good memory for finding flowers, and a proboscis, or tongue, for attaining nectar. Animal pollination has obvious advantages for plants. Many pollinators cover great distances, which insures genetic diversity through outcrossing, or the transfer of pollen to unrelated individuals.
The pollinator benefits as well by gaining access to a source of food. The relationship of pollinator plant is an example of mutualism. Imperiled Pollinators All is not well in the realm of pollinators. The age-old relationships between plants and pollinators is threatened, especially in urbanized and agricultural regions. Habitat destruction and fragmentation, pesticide abuse, and disease all have taken their toll on pollinators.
As more land is cleared for human habitation, bees, butterflies, bats, and birds are left homeless. Our gardens offer little to sustain them. They need a constant source of nectar and pollen throughout the entire season. The few flowering plants most people grow will not suffice.
A related problem is fragmentation of plant communities. Plants must be pollinated in order to set seed for the next generation.
Plant/Animal Relationships - Brooklyn Botanic Garden
Without pollinators, no seed is set and the plants eventually die out, leading to local extinction. Isolated patches of forest, grassland, or desert are particularly vulnerable. A small patch may not sustain enough pollinators, or may be too far from other patches for pollinators to travel. As a result, plants do not reproduce. Pesticides have also reduced pollinator populations. Bees are often killed by chemicals applied to eliminate other pests.
Honeybees are being destroyed by diseases and parasitic mites. The crisis is not just affecting native ecosystems.
Fruit trees and many other food crops depend on pollination for production. We stand to lose over three quarters of our edible crops if we lose pollinators.
What can be done? Encourage pollinators by planting a diverse mixture of adult and larval food plants in your garden.