Community Ecology Flashcards
consumption
+/- interaction when one species eats another
competition
-/- interaction when two species competes for the same limiting resource
commensalism
+/0 interaction when one species benefits and the other is unaffected
mutualism
+/+ interaction when both species benefit
amensalism
-/0 interaction when on species is harmed and the other is unaffected
three forms of consumption
herbivory, parasitism, predation
herbivory
one species eats plants i.e. caterpillars
parasitism
one species eats small amount of host i.e. ticks
predation
one species kills and consumes all or most of another individual
consumption selects for traits that allow
individuals to avoid being eaten
constitutive defense
defenses that are present even in the absence of predators
examples of constitutive defense
cryptic coloration (camoflauge), production of toxins/defense chemicals (poison dart frogs), defense armor (sea urchins)
predation can select for similar phenotypes
across different species in the same environment
milk snake and coral snake
milk snake is not venomous, coral snake is; coloration is similar so that milk snake is predated on less often
batesian mimicry
mimics look dangerous but are not dangerous
example of batesian mimicry
hornet moth, wasp beetle, hoverfly
mullerian mimicry
mimics look dangerous and are dangerous
example of mullerian mimicry
paper wasp, bumblebee, honeybee
why mullerian mimicry
strength in numbers - re-enforces to the predators
species turn on some defenses only
in the presence of a predator
inducible defenses
defenses in response to predator
example of inducible defense
mussles grown in presence of crab (that ate fish not mussels) led to increase in shell thickness of mussels
why do rough-skinned newts produce such lethal toxin
garter snakes (predator) evolved resistance to the toxin
if variation for toxin levels in newts, which newts have higher fitness
newts with the higher levels of toxin (directional selection)
which snakes would have highest level of fitness
snakes with most resistance to toxin (directional selection)
so-evolutionary arms race
repeating cycle of reciprocal adaptation (newts and snakes)
red queen hypothesis
species must constantly evolve so they are not driven to extinction by predation, parasitism, or herbivory
human defense against plasmodium
liver cell has HLA-B53 protein that displays cp26 when infected by plasmodium - T cells destroy the infected cell
evolution of plasmodium
mutated cp26 protein that does not induce immune response
top-down hypothesis
predators and parasites remove herbivores that eat plants
bottom-up hypothesis
herbivores are limited because plant tissues are low in nutrients (limits population growth) and plant tissues well defended
why are plants so abundant despite constant consumption
top-down and bottom-up hypothesis
how do plants defend themselves
morphological armor and toxin production
plants engaged in co-evolutionary arms race with
predators - production of toxin and selection for resistance
example of top-down hypothesis in plants
plants and parasitic wasps - mutualism - inducible
overlapping niches lead to
competition
niche
range of resources that a species can use or range of conditionx it can tolerate
competition influences
distribution and abundance of species
if competition is symmetric
both species will persist in the area of overlap likely in reduced numbers
if competition is assymetric
the species that is most fit in the area of overlap will persist and the other species will go extinct in that area
competitive exclusion
two species that occupy the same identical niche cannot co-exist - but if there is complete overlap the weaker species can retreat to another area of the niche
larvae of both barnacles exist in the lower intertidal zone - why are Chthalmalus adults only in the upper tidal zone
they are outcompeted by Semibalanus
half of rock had both Chthalmalus and Semibalanus, one only had Chthalmalus
monitor survival of Chathlmalus - when competitor absent, Chathlmalus grows well
fundamental niche
total theoretical range of environmental conditions a species can tolerate
realized niche
portion of fundamental niche that is actually occupied
fundamental vs realized niche in chthalmalus
fundamental is upper and lower intertidal zone - realized is only upper intertidal zone
competition vs survivor in barnacles
semibalanus is good competitor, chthalmalus is good survivor - life history, natural selection, energy trade-off
niche differentiation, resource partitioning, specialization
evolutionary change in fundamental niche is driven by competition - natural selection favors individuals who don’t have to compete
niche differentation results from
character displacement
character displacement
evolutionary changes in traits that allow species to exploit different resources - leads to niche differentiation
example of commensalism
ants stir up insects while hunting - antbirds follow to catch the insects that fly away (bird benefitting, ants unaffected)
what environmental factor could shift the ant-antbird from +/0 to +/- interaction
antbirds accidentally eat many ants while chasing down other insects OR antbirds step in path of ants forcing ants to expend more energy to crawl over their feet
clownfish-sea anenome is not always commensalism
waste product of clownfish is nutrition for sea-anenome (+/+) or clownfish can steal food source from sea-anenome (+/-)
plant-mycorrhizae
mutualism plants get more nutrients and water, fungus gets carbon and place to grow
ant-acacia
mutualism - ant gets housing and food, acacia tree gets protection from herbivores (ants mob and attack herbivores that try to eat the tree)
treehopper-ant
mutualism - treehoppers suck sap from plants and produce honeydew which is shared food source with ants - ants protect treehoppers from predators
is treehopper-ant interaction always mutualistic
no - relationship is mutualistic when jumping spiders (predators to treehoppers) are present
when is treehopper-ant relationship not mutualistic
when jumping spiders are not present (commensalism)
example of amensalism
insects squashed by stampedes, grass crushed by migration, algal blooms killing marine species (but not beenfit to algae)
two ways to describe community structure
total number of species (species richness) and species diversity
speceis richness
total number of species in a community
relative abundance
proportion each species contributes to the total number of individuals of all species in the community (pi)
relative abundance equation
number of individuals of species 1 / total number of individuals
shannon diversity
takes into account number of species in a community and the disctribution of those species
keystone species have
a disproportionate impact on the abundance of other species (environment engineers)
starfish keystone species
starfish feed on mussels - without starfish present the species richness drops drastically
disturbance
stonrg short-lived disruption to a community that changes abundance and distribution of biotic and abiotic components
disturbance characterized by
type, frequency, and severity
giant sequoia disturbance
20-40 low severity forest fires per century
community structure is maintained by
a disturbed regime
effect of Smokey the Bear campaign
fewer forest fires but now more severe
prescribed burn
burn the dead stuff on the ground
what prevents severe forest fires
prescribed burn and thinning
succession
gradual colonization of a habitat after a disturbance usually by a series of species
stages of succession
pioneering species, early successional community, mid-succcessional community, climax community
primary succession occurs when
disturbance removes the soil and soil organisms along with surface organisms
examples of primary succession
glaciers, floods, volcanic eruption
first steps of primary succession
production of soil and colonization of microbes
next few steps of primary succession
mosses, lichens, etc. grow - die - increases organic matter, more species colonize
secondary succession occurs when
disturbance gets rid of surface organisms but soil is in tact
examples of secondary succession
fire, logging, hurricane
what type of life history species will do well after secondary succession
r-strategists - high fecundity, low survivorship
what type of life history species will do well in late successional species
k-strategists - good competitors, low fecundity, high survivorship
existing species can affect colonization by
subsequent species
two ways existing species affects colonization of subsequent species
facilitation and inhibition
facilitation
early-arriving species make conditions more favorable of later species (increase organic matter, etc.)
inhibition
presence of one species inhibiits the establishment of another species
why is species succession somewhat unpredictable
environmental and historical context, and chance events
