Herbivory: effects on plant abundance, distribution and population growth
Request PDF on ResearchGate | Interactions between plants and the relationship between plants and herbivores, including the defensive. This 'battle' between animals and plants is likened to an arms race and has led to strong relationships between many herbivores and plants. Nevertheless, when examined at the community scale across sympatric species, the relationships between chemical defense and herbivory are.
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.
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. Erect bat and bird houses, as well as bee hives. Reduce or eliminate pesticide use.
Help restore native plant communities not only in your yard, but also in parks and along roadways, and connect them through corridors to preserves and other natural areas. Plants and Their Dispersers No two plants can occupy the same spot. In order to have room to grow, seeds must be dispersed away from the parent plant.
Seed dispersal is accomplished by a variety of means, including wind, water, and animals. Animal dispersal is accomplished by two different methods: Animals consume a wide variety of fruits, and in so doing disperse the seeds in their droppings. Many seeds benefit not only from the dispersal, but the trip through the intestine as well. Digestive acids scarify seeds, helping them to break out of thick seed coats.
Some seeds are armed with hooks and barbs that enable them to lodge in the fur of animals that brush past them. Beggar's ticks and bur marigold are two examples. Eventually, the seeds are rubbed or scratched off, and may find a suitable spot on which to germinate and grow.
Herbivory: eating plants - The Australian Museum
People are important for dispersing plants, too. The common weed plantain was called "white man's footsteps" by Native Americans because wherever settlers walked, the plantain came in the mud on their shoes. Some Animals and the Plants They Disperse Ants - Many wildflowers, such as trilliums, bloodroot, violets Birds - Fleshy fruits and grains, such as baneberry, viburnums, mountain ash Clark's Nutcracker - Whitebark pine Mammals - Fruits, grains, nuts, berries Squirrel - Nuts, such as those of oaks, hickories, pines Fox - Berries, such as blackberry, grapes Humans - Weeds such as plantain, dandelion, lamb's-quarters Reptiles - Fleshy fruits, especially berries such as strawberry, groundcherry, jack-in-the-pulpit Mutualism Mutualism is an obligate interaction between organisms that requires contributions from both organisms and in which both benefit.
There are many examples in nature. Pollination and dispersal, discussed above, are mutualistic because both plant and pollinator or disperser benefit from the relationship. The relationship between mycorrhizal fungi and many higher plants is another common example of mutualism. The bodies of the fungi, called hyphae, live on or in the tissues of plants, and make nutrients available for the plants to absorb.
Positive interactions between herbivores and plant diversity shape forest regeneration
The plants provide the fungi with amino acids and other complex compounds. One of the most celebrated examples is the orchids. Whereas some plants may support as many as different fungi, orchids have quite specific mycorrhizal associations. Different plant communities have different mycorrhizal associations.
The microflora of a grassland is different from that of a forest. These differences, at least in part, may influence the distribution of plant communities.
The Lovely Lady-slipper The reason lady-slipper orchids are so hard to grow in a garden is that the needs of both the orchid and its fungus must be attended to. 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.
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. 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. They can also physically damage corals with scrapes. Insect crop damages also contribute largely to annual crop losses in the U. For example, the hunting of herbivorous game species such as white-tailed deer, cottontail rabbits, antelope, and elk in the U.