Ecology Chapter 15: Population and Herbivory

Introduced, exotic, or nonnative species

Species introduced to a region where they have not previously existed

Invasive species

Introduced species that spread rapidly and negatively affect other species

Parastoids

Larave hatch and consume tissues of living hosts

Mesopredators

Small carnivores that consumbe herbivores

Top predators

Typically consume both herbivores and predators

Lotka-Volterra model

Model of predator-prey interactions that incorporates changes in numbers of predators and prey

Growth of prey populations

Depends on the growth rate of prey (rN) and the rate of individuals killed by predators (cNP)

N

Number of prey

P

number of predators

c

probability of an encounter between a predatory and prey

Equation for the growth of prey populations

dN/dt = rN - cNP

Growth of predator populations

Depends on growth rate of predators (acNP) minus the rate of predator death (mP)

a

Efficiency of a predator converting consumed prey into predator offspring

m

per capita mortality rate of predators

Equation for the growth rate of predators

dP/dt = acNP - mP

Numerical response

Change in the number of predators through reproduction, immigration, or emigration in response to prey numbers

Functional response

Relationship between the density of prey and predators’ rate of food consumption

Type 1 functional response

Predator’s rate of prey consumption increases in a linear fashion with an increase in prey density, until satiation

Type 2 functional response

Predator’s rate of prey consumption begins to slow as prey density increases, and then plateaus; often because predators must spend more time handling prey

Type 3 functional response

Predator exhibits low, rapid, and slowing prey consumption with low, moderate, and high densities; predators may not be not be skilled at catching prey at low densities, or prey have plenty of resources

Active hunting

Predators spend most of their time moving and searching for prey

Ambush hunting

Predators lie in wait for prey to pass by

Alarm calling

Warning relatives that predators are approaching

Spatial avoidance

Prey move away from predators

Crypsis

Camouflage that allows an individual to match its environment or break up the outline of an individual

Structural defense

Defense mechanism that reduces a predator’s ability to capture, attack, or handle prey

Chemical defense

Defense mechanism that provides prey a chemical weapon to defend themselves

Aposematism

Warning coloration where distastefulness evolves in association with very conspicuous colors and patterns

Batesian mimicry

Palatable species evolve warning coloration that resembles unpalatable species

Mullerian mimicry

Several unpalatable species evolve a similar pattern of warning coloration

Coevolution

2 or more species affect each other’s evolutions; selection for prey defenses will favor the selection for counter-adaptation in predators

Structural defense

Deters herbivores from consuming plant parts

Chemical defense

Chemical formulas that deter herbivores from eating plants, including sticky resins, latex compounds, and alkaloids