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Community Ecology (Metapopulations in Patchy Environments (If several…
Community Ecology
Metapopulations in Patchy Environments
If several local populations are interconnected by migration
& gene flow between the patches,
the local populations constitute a metapopulation
The high-quality patch is a source habitat
the low-quality one is a sink habitat
fugitive species
one that survives by colonizing new patches, flourishing temporarily,
then colonizing more patches before it dies out in old ones
assisted dispersal
animals are captured in one area & released into the new area
Interconnectedness of Species: Food Chains and Food Webs
3 trophic levels
primary producers (plants, algae, cyanobacteria)
primary consumers (herbivores)
secondary consumers (carnivores)
food chain
direct line of consumption
food web
network of numerous interrelationships
energy flow web
to trace how energy flows through the community
keystone species
the presence or absence of certain species
Predator–Prey Interactions
One Predator, One Prey
one species of prey, such as a plant,
is attacked by only one species of predator
such as an herbivore
helps us understand how we human predators should harvest our various prey
2 fundamental aspects
predator’s feeding rate
how quickly a predator find a new prey individual
functional response
handling time
amount of time needed to actually consume the prey
functional response
Predator Selection Among Multiple Prey
most animals, especially vertebrate herbivores
can & will eat a variety of plants & omnivores eat both plants & animals
3 factors
probability that a particular prey individual will be encountered
the decision by the predator to attack an individual once it has been encountered
the probability that an attacked prey item will be successfully eaten
optimal foraging theory
examine the interactions between these factors in an attempt to
understand why herbivores eat the plants they do while ignoring others
Competition Between Species
Several species often compete for the same resources
exploitation competition
resource competition occurs
when organisms consume a shared resource
making it less available for other organisms
interference competition
one organism restricts another organism’s
access to resources
even though the first might not be using it
If a species can increase from very low population density
even w/ its competitor present,
then that species can be invasive
Apparent Competition
plants are not actually competing for & using a resource
Concepts
community
group of species occur together @ same time & place
succession
predictable sequence of changes
climax community
disturbed patch undergoes succession
until it becomes spruce-fir forest again
community restoration
ex: reintroducing wolves into Yellowstone National Park
Beneficial Interactions Between Species
mutualism/mutualistic relationship
If 2 organisms interact such that both benefit
ex: pollinators and the plants they pollinate
facilitation
If one organism helps another without receiving any benefit
the first organism facilitates the presence of the other
plays a role in primary succession
organisms become established on newly created substrates
Nurse plants
plants that alter a small area of habitat
immediately below themselves so that it is more favorable
to the survival of seedlings of other plants
as compared to other nearby areas not below the nurse plant
Diversity
Diversity & Scale
Larger areas are more diverse than smaller ones
scale matters
higher diversity in larger areas is common
species-area relationship
relationship between area & species richness
S = cAz
species abundance distribution
plot the number of species in each abundance class
Diversity &Latitude
far northern areas have fewer species
tropical regions near the equator have benign environments
& those at higher latitudes have more severe conditions
Near the equator, temperatures are always warm
freezing conditions are rare except on the highest mountains
Plants do not have to be adapted to survive freezing or water stress
