Exploitation High Low Intimacy Parasitoids Parasite Predator Grazer
- Slides: 39
Exploitation
High Low Intimacy Parasitoids Parasite Predator Grazer Low Lethality High
There are 4 general categories • “True” predators • Herbivores – Grazers – Browsers – Granivores – Frugivores • Parasites • Parasitoids
“True” predators
Herbivores – Attack many prey items in a lifetime – Consume only a bit of the victim – Do not usually kill prey in the short term (but may do so in the long term) • Grazer • Browser • Granivore • Frugivore
Parasites • Consume part of their prey • Do not usually kill their prey • Attack one or very few prey items in their lifetime • Parasitoids
Parasites • Parasitoids – which straddle the parasite and true predator categories - they lay eggs inside their host which they eventually kill
Predation is important because: 1. It may restrict the distribution of, or reduce the abundance of the prey species. 2. Predation, along with competition, is a major type of interaction that can influence the organization of communities. 3. Predation is a major selective force, and many adaptations of organisms have their explanation in predator-prey coevolution. 1. Evolutionary arms race 4. Predation drives the movement of energy and nutrients in ecosystems.
Alfred Lotka (1880 -1949) Vito Volterra (1860 -1940)
start Predation • Rate of increase of prey population d. H/dt = r. H
Predation • Rate of increase of prey population – d. H/dt = r. H – Predators eat prey • d. H/dt = r. H-a'HP – a' = capture coefficient – H = Prey pop size – P = Predator pop size
Predation • Rate of increase of predator populations d. P/dt = -q. P – If only predators exist, no prey, so predators die
Predation • Rate of increase of predator populations d. P/dt = -q. P – If only predators exist, no prey, so predators die • d. P/dt = fa’HP-q. P – f = is a predation constant » Predator’s efficiency at turning food into predator offspring. – a' = capture coefficient – q = mortality rate
Predation • Equilibrium population sizes – Predator • • • d. P/dt = fa’HP -q. P 0= fa’HP -q. P fa’HP = q. P fa’H= q/fa’ – Prey • • • d. H/dt = r. H-a’HP 0= r. H-a’HP r. H= a’HP r = a’P P = r/ a’
Predation • Graphical Equilibrium – Prey (H) equilibrium (d. H/dt=0) is determined by predator population size. – If the predator population size is large the prey population will go extinct – If the predator population is small the prey population size increases Predator Pop size d. H/dt =0 r/a’ Prey pop size
Predation d. P/dt =0 • Graphical Equilibrium Predator Pop size q/fa’ Prey pop size – Predator (P) equilibrium (d. P/dt=0) is determined by prey population size. – If the prey population size is large the predator population will increase – If the prey population is small the predator population goes extinct
Predation • Predator-Prey interaction – The stable dynamic of predators and prey is a cycle d. P/dt =0 Predator Pop size r/a’ q/fa’ Prey pop size
Do these models apply to natural populations? • Lynx/Snowshoe Hare - Arctic system where there is one predator and one prey
Lynx/Snowshoe Hare Arctic system where there is one predator and one prey Assumptions?
Rosenzweig & Mac. Arthur (1963) • Three possible outcomes of interactions • The oscillations are stable (classical oscillations of Lotka-Volterra equations). • The oscillations are damped (convergent oscillation). • The oscillations are divergent and can lead to extinction.
i) Prey iscoline Predator density N 2 Prey increase ii) Predator iscoline Prey density K 1 N 2 Predator density K 2 Predator decreases Predator increases Prey density N 1
Predator-Prey Models – Superimpose prey and predator isoclines • One stable point emerges: the intersection of the lines • Three general cases a) Predator isocline Population density Predator Density – Inefficient predators require high densities of prey Damped oscillations Prey isocline Prey Density Time
Predator-Prey Models • Three general cases (cont. ) Predator Density b) Predator equilibrium density Prey Density Population density – A moderately efficient predator leads to stable oscillations of predator and prey populations Stable oscillations Time
Predator-Prey Models • Three general cases (cont. ) Predator density Population density – A highly efficient predator can exploit a prey nearly down to its limiting rareness Prey Density Increasing oscillations Time
All these models make a series of simplifying assumptions • A homogenous world in which there are no refuges for the prey or different habitats. • There is one predator species eating one prey species and there are no other species involved in the dynamics of these two populations • Relaxing these assumptions leads to more complex, but more realistic models. • All predators respond to prey in the same fashion regardless of density – Functional Response
Conclusions form field studies • There is not a clear relationship between predator abundance and prey population size. – In some, but not all cases, the abundance of predators does influence the abundance of their prey in field populations.
What makes predators effective in controlling their prey? • Foraging efficieny – Within a patch, the searching efficiency of a predator becomes crucial to its success. – But searching efficiency varies with abiotic factors and can also decrease at high predator densities because of interference of other predators.
Predation • Response of predator to prey density – Numerical – Aggregative – Functional
Types of functional responses • Limited by handling time • The rate of capture by predator • Alters Behavior –Type III Eat all you want Eat all you can, if you can find it! C. S. Holling (1930–)
Types of functional responses Slide 25
Not all predators are created equal
Keystone predator • Bob Paine at University of Washington mussel is a competitive dominant in this system
Keystone predator absent
Keystone predator present
Other examples of keystone predators
Keystone predator absent
Keystone predator present
The effects of herbivory • Individual plants are affected in the following areas – plant defenses – plant compensation • plant growth • plant fecundity
Chemicals Defenses • Quantitative Defenses: • Qualitative Defenses: • Prevent digestion as they accumulate in the gut. • Usually found in large quantities in the plant parts that are eaten. • Most of these compounds are “Carbon Rich” • Common defense of plants growing in nutrient poor soils (conifers). • Usually toxic in small quantities. • Found in relatively small amounts in the portion of plants that is eaten (leaves). • These compounds are “Nitrogen Rich” and therefor expensive to produce by the plant. • More common in plants growing on nutrient rich soils.
- Grazer uhrturm
- Mid low high
- Emotive style communication
- Significant figures
- Low voltage hazards
- Tropical rainforest consumers
- Oscillations
- Example of predator
- Keystone species definition biology
- Sagittiform fish examples
- Taeniform body shape
- Adaptation of predators
- Predator-prey examples
- Predator ecology
- Terry richardson pervert
- Ck wraps
- Predator prey cycle
- Predator prey relationship in temperate deciduous forest
- Robert e. ricklefs
- Animal skull identification
- Suurpedot
- Food chain apex predator
- The symbiotic relationship between the ra
- Commensalism relationship examples
- What std are curable
- An unlikely parasite: the mistletoe answer key
- Tremotoda
- Calliphoridae
- Mud shrimp parasite
- Double chromatin dots malaria
- How many herbivores are there
- Do beetles taste like apples
- Parasite structure
- Parasite std
- Parasite in blood smear
- Hyminoptera
- Ascaris lumbricoides infective stage
- Source
- Aswin djoko baskoro
- Aleurocanthus woglumi