Herbivory

herbivory

a type of exploitative itneraction

true or not true predators?

most herbivores are not TRUE predators because they often do not kill the plants they eat

example: snowshoe hares nibble on leafy parts of plants and plants can regrow

example of herbivore that IS a true predator

California vole graze on seedlings down to the base of their stems which kill the plants

granivores are also predators because they kill and consume the seeds

herbivory

an exploitation relationship.

grazers specialize on herbaceous plants (grasses, herbs)

browsers specialize on leaves, bark, and twigs of woody plants

granivores specialize on seeds

frugivores specialize on fruits

plant defenses against herbivory

1. chemical

2. mechanical

3. nutritional

4. tolerance

chemical plant defense against herbivory

producing chemicals that are noxious or poisonous to herbivores

ex. wild chilies have a very spicy taste, mice don’t like that

mechanical plant defense against herbivory

developing structures like thorns that make it harder for animals to eat them

ex. some trees have thorns on trunk and branches that deter browsers

nutritional chemical plant defense against herbivory

growing structures that are less nutritious for grazers (have less N and P)

ex. some plants have less nutrition and are harder to digest b/c of cellulose

tolerance chemical plant defense against herbivory

adaptions to regrow quickly after being grazed

Ex. some plants can regrow the parts that were eaten or allocate resources to healthy parts

plants subject to heavy grazing can better recover from damages than those who aren’t subject to heavy grazing

herbivory affecting plant communities

herbivores can increase plant diversity if they feed on plants that outcompete others.

e.g. Walter Carson and Richard Root experiment on beetles and goldenrod plants that outcompete other plants. beetles opened up space and light resources for other plants, increasing diversity. more than the insecticide plots