CH 26: Community Ecology
Diversity
Concept
community
community must have boundaries
projects in community restoration
habitat fragmentation
humans are the most destructive species
climax community
Diversity and Scale #
Communities consist of more than one species
diversity of growth forms may be the focus
larger areas are more diverse
relationship between area and species richness
(S=cA^z) species-area relationship
no community will have equal numbers of individuals
species abundance distribution
most species are sparse
several species are rare
Diversity and Latitude
regions near equator have benign environments
plants dont have to adapt to water stress or cold weather
low plant diversity in high latitudes
evolutionary history is a fundamental contributor
well protected resting buds are needed
vascular cambium must become dormant in the winter
Predator-Prey Interactions
One Predator, One Prey
primary producer attacked by a herbivore
functional response
prey-dependent
Lotka-Volterra model=(dN/dt=rN-aNP)
dN/dt= rate of change with time of prey population
r=intrinsic rate of increase for prey species
N=number of individuals of prey species in community
a=predators per capita attack rate
P= number of predator individual present
(dP/dt=faNP-qP) rate of change of predator population
dP/dt=change with time of predator population
f= converting the prey it has eaten into new predators
q= predators per capita mortality rate
population is stable when dP/dt=0
line indicating population stability is called zero growth isocline
paradox of enrichment
Predator Selection Among Multiple Prey
probability that a particular prey individual will be encountered
multiple plant species that are prey to herbivorous predators
decision by the predator to attack an individual
probability that an attacked prey item will be successfully eaten
optimal diet model that makes 4 predictions
one plant species competes with another plant species
exploitation competition
interference competition
two competing species can coexists in a community
resources a factor that can increase growth rate
temperature is not a resource
Beneficial Interactions Between Species
mutualism where two organisms interact and it benefits both
pollinators
first organism facilitates the presence of the other
mutualisms incur a cost
primary succession=newly created substrates
Metapopulations in Patchy Environments
world is patchy and heterogeneous
4 assumptions of metapopulation
high quality patch=source habitat #
low quality patch= sink habitat
empty patches are not surplus
fugitive species survives by colonizing patches
migration between patches is important #
assisted migration=animals captured and released into new
Interconnectedness of species
three trophic levels
food chain
food web
energy flow webs are hard to construct for real communities
keystone species: affects the structures to their community
sea otters are a keystone species #
behavior can change depending on the species around
ponds benefit plants but not beavers