BIOL-208 Lecture Notes - Lecture 14: Snow Goose, Caddisfly, Herbivore
17 Dec 2016
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Herbivory and Predation
- Exploitation
- Defined as the interaction between populations that enhances fitness of one
individual while reducing fitness of the exploited individual
- Herbivores consume live plant material but usually do not kill plants
- Predators kill and consume other organisms
- Herbivory and plant defence
- Herbivory widespread: evolution of diversity of plant defense strategies
- Meta analysis (81 studies)
- Bernivory decreases plant growth and reproduction but
- In grasses or sedges, growth rates often increase after herbivory if
nutrients are abundant
- Snow goose grazing and a sub-arctic salt marsh
- Increased productivity
- Despite reduced standing biomass
- Leads to overcompensation
- Why overcompensation?
- Differences in grazing intensity
- Defecation from grazers provides nutrients
- Plants may be affected differently by grazing depending on time of
year
- Grazing reduced the amount of plant biomass found at any point in time
but increased the total productivity of the system over the course of the
growing season
- Herbivorous stream insect and its algal food
- Caddisflies are algae and bacteria grazers
- Excluding caddisflies resulted in increased numbers of bacteria and
increased algal biomass
- Plant defenses
- Plants that have reduced fitness due to herbivory will be under natural
selection to increase resistance (such as thorns) and tolerance
- Morphological defences are widespread
- Giraffe eating leaves from a tree, tree grows thorns, giraffe has
tough enough tongue to withstand thorns. Probably co evolved
- Chemical defences are common
- Toxins: chemicals that kill, impair, or repel
- Digestion reducing substances: inhibit breakdown of plant proteins
by digestive enzymes (this is common in invertebrates)
- Two types of plant defences
- Constitutive: continuous, regardless of environment
- Induced: rapid increase in response to damage
- Impacts of predators on prey populations
- Prey populations are affected by
- Food availability
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Document Summary
Defined as the interaction between populations that enhances fitness of one individual while reducing fitness of the exploited individual. Herbivores consume live plant material but usually do not kill plants. Herbivory widespread: evolution of diversity of plant defense strategies. Bernivory decreases plant growth and reproduction but. In grasses or sedges, growth rates often increase after herbivory if nutrients are abundant. Snow goose grazing and a sub-arctic salt marsh. Plants may be affected differently by grazing depending on time of year. Grazing reduced the amount of plant biomass found at any point in time but increased the total productivity of the system over the course of the growing season. Herbivorous stream insect and its algal food. Excluding caddisflies resulted in increased numbers of bacteria and increased algal biomass. Plants that have reduced fitness due to herbivory will be under natural selection to increase resistance (such as thorns) and tolerance.
