Community ecology Flashcards
Community
Interacting species within a defined area
Interactions
Species interactions
types
Competition (-/-)
Consumption (+/-)
Mutualism (+/+)
Commensalism (+/0)
Labels
Can be either a + or a –
A + or a – to fitness leads to a + or a – to population number
Studies of species interactions focus on the interaction’s influence on the fitness of the organisms
Species interactions
Can affect the distribution and abundance of a particular species
Can lead to natural selection
Coevolutionary arms race
The outcome of each interaction is dynamic and conditional
Competition
intraspecific
within species
Space, food, light, mates
Density dependent intensity
Is a major cause of density dependent growth
competition
interspecific
different species encounter an overlap in their niches
Niche
A range of resources the organism can use
A range of conditions it can tolerate
Niche overlap leads
to competition
Complete niche overlap
Species in the same niche can not coexist
Called the competitive exclusion principle
G. F. Gause
If there is asymmetric competition then one will outcompete the other and cause the other to go extinct
Niche differentiation
No one wants to compete forever
Also called resource partitioning
Leads to character displacement
Competition on a community level
influenced the population
How does studying competition help in conservation studies?
Invasive species
Maintaining current interactions
If an ecosystem is highly diverse then invasive species have less of an impact because of the number and amount of competitive interactions
Prey steps versus predator steps
Detect predator
Avoid detection
Avoid capture
Get back at the predator
- Detect prey while avoiding detection
- Catch prey
- Consume prey
Herbivory
Consumption of plant tissues
Parasitism
Consumption of a host by a parasite
Long period of time
Piece by piece
Isn’t the only type of parasitism
Predation
When a predator kills and consumes most or all of another individual
Constitutive defenses
Escape
Hiding
Poison
Bad taste or bad coloration
Schooling
Flocking
Weaponry: spines, hooves etc
Natural selection favors the prey that can not get eaten
consumption
Causes the prey to lose fitness
Prey put up a fight
One organism eats the other
Herbivory
Parasitism
Predation
Mimicry
1 species closely resembles another
Mullerian mimicry
both species are harmful and they look like each other
Batesian mimicry
one is harmful, but they still look alike
Inducible defenses
Constitutive defenses are expensive
only occur in the presence of a predator
Efficient energetically but slow and necessary to produce
They decrease with the decrease in the predator population
Why don’t prey die out?
Prey are naturally selected to survive
Smaller
Larger clutch sizes
Reproduce younger
Large intrinsic growth rates
Predators do decrease the population significantly however
Exp: wolves in alaska
Why don’t herbivores eat everything?
Limiting impacts on herbivory include, nitrogen limitations, predation or top down control, and defenses by the plants
Well defended but offer better nutrition
Won’t survive well if they are not preyed on
Predator prey arms race
Since prey are selected to escape
predators are selected to capture
Two species co evolve
increase their fitness
Consider malaria and humans
Conservation
Predator and parasite studies have lead to biocontrol mechanisms
Integrated pest management
Mutualism
Pollinators
Fungi and roots
Nitrogen fixing bacteria and plants
Farmer ants and fungi
dynamic
One change in the ecosystem can lead to the relationship being irrelevant and unnecessary
Natural selection and mutualism
The species are not being nice
Nature is selfish
If one stops paying out the other will stop too
Reciprocal parasitism
Commensalism
Not well studied
Difficult to identify
Remoras and sharks
Barnacles and whales
Each relationship is fluid and dynamic
Dependent on stable conditions and variables
