Prey-Predator Models Flashcards
(16 cards)
When does coexistence happen?
In single population logistic growth, density dependence allows coexistence among individuals and a stable population at the carrying capacity
In the Lokta-Volterra models, coexistence happens when intraspecific density dependence is stronger than interspecific interactions
In predator-prey/ consumer-resoruces interactions, get coexistence when there is a type 3 functional response or there is strong intraspecific competition in prey or predator
What are the two sources of density dependence?
Intraspecific competition
Predation rate that increases with prey density
What does the functional response represent?
In population dynamics, response represents a loss to the prey population
Losses = mortality
What is the type 1 functional response curve?
Number eaten increases with prey density
Gradient = mortality rate
The functional response is constant
Density INDEPENDENT mortality
What is a type 2 functional response?
Number of prey eaten increases with prey density but at a decreasing rate as the predators hit digestive capacity
Gradient is mortality rate
Mortality rate decreases in this functional response
Inverse density dependence
What is a type 3 functional response?
Number of prey eaten increases exponentially with increasing prey density and then saturates as they get full
So predator starts eating disproportionately more prey as their density increases
Gradient = mortality rate
Increases with density and then decraeses
There is negative feedback by the predators on prey and low density - known as predator induced density dependence
Inverse density dependece at higher densities
Which functional response is most common? Why is this unusual?
Type 2 e.g. slugs feeding on grass
Predators do not regulate prey by generating density dependent mortality in prey numbers
Predation is likely to destabilise
What are the ways energy from prey is lost through trophic levels?
Partial feeding
Excretion and processing
Allocation to metabolism and growth before reproduction
Lose 10-50%
𝜀 = energy conversion rate
What is the equation for predator growth?
𝜀 x Functional Response x Predator Number
What is the most simple model possible? What happens at equlibrium?
Prey growth function = exponential
Function response = type 1
At equilibrium the species may coexist and PGR = 0
What is wrong with the simple model?
No density dependence negative feedback
No real equilibrium between predator and prey
Exponential growth and type 1 are not commonly seen in nature
When does stabilisation happen in logisitc type 2 curves?
Predator ZNG1 close to prey K = means predator is inefficient
This means they need lots of prey
That means it can be stabilised by density dependence in prey growth
Get destabilisation when ZNG1 far from prey K - means it is an efficient predator
How can predation affect biodiversity with examples
Predation can decrease biodiversity - seen in mosquito larvae and protists
Predation can increase biodiversity by targeting dominant competitors - seen in starfish and grazing rabbits
Predators can alter rank and relative abundance without affecting biodiversity - seenn in newts and tadpoles
Predation can change competitive dominance - seen in periwinkles and macroalgae
Give the links between predation and biodiversity
Keystone predation targeting the dominant competitor can increase diversity
Keystone predation targeting weakest competitors can lower diversity
Generalist predation can also lower diversity
Predation can change ranking of competitors without changing diversity
Context dependent
What is a trophic cascade?
Indirect interactions between non-adjacent trophic levels
