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Ch 55 Community Ecology
Terms in this set (34)
consists of all the species that interact in a certain area
when one species benefits but the other species is unaffected (+/0)
-difficult to quantify
Ex. antbirds follow ants and eat/pickoff the insects that ants do not
when individuals use the same resources, resulting in lower fitness for both (-/-)
competition within species
for space, sunlight, food,other resources
-major cause of density dependent growth
when individuals from different species use the same limiting resources
-occurs when niches of two species overlap
if both species experience a similar decrease in fitness because of overlap of niches
when one species suffers a greater fitness decline than the other species does
Competitive exclusion principle
Gause proposed that two species that occupy the exact same niche cannot coexist
• One of the species must locally go extinct. (locally=from that region or area).
the total theoretical range of environmental conditions that a species can tolerate
portion of the fundamental niche that a species actually occupies, given limiting factors such as competition with other species
Experimental Studies of competition in nature
chthalmaus in upper intertidal zone (more severe environment bc it is exposed to the air and intense heat for longer periods) and semibalanus were only in the lower intertidal zone.
barnacles are stuck to rocks but young are mobile
young of both species were found together in the lower zone.
1. adult upper tidal are outcompted in the lower area
2. adult upper tidal are absent from the lower bc they do not thrive in those environments
Why is the distribution of adult Chthamalus restricted to the upper intertidal zone?
-transplant rocks containing young Chthalmus to lower zone
-let Semibalanus colonize the rocks
-remove Semibalanus from half of each rock. moniter survival of Chthalmus on both sides
-chthamalus will surivive better in absence of semibalanus
conclusion: chthalmus do not occur in lower interridal zone bc they are outcompeted by semibalanus
the range of resources that the species is able to use, or the range of conditions that it can tolerate
ex. Anolis lizard that occupy the crowns of trees on Jamaica occupy a different niche than the ones that live on the ground
when one organism eats or absorbs nutrients from another (herbivory, predation, and parasitism) (+/-)
when two species interact in a way that confers fitness benefits to both (+/+)
• Pollinators get food plants get sex
• Cleaner fish and shrinmp do this, fish clean food from mouths of bigger fish. Cleaner stations allow "client fish" to get parasites removed by cleaner fish. Its understood that they wont eat the cleaner fish.
Species interactions can affect the distribution and abundance of a particular species
Species act as agents of natural selection when they interact
coevolutionary arms race
- a repeating cycle of reciprocal adaptation
the outcome of interactions among species is dynamic and conditional
interactions between different organisms may change over time and space
fitness trade offs
-inevitable compromises in adaptations
-reason why semibalanus and other successful competitors haven't taken over the world
-if indviduals are extremely good at competing for a particular resource, then they are probably not as good at enduring drought conditions, warding off disease, or preventing predation
Mechanisms of coexistance: niche differentiation
-evolutionary change in resource use caused by competition over generations
-the evolutionary change that occurs in species traits and enables species to exploit different resources
-makes niche differentiation possible
ex. Galapagos finches-specializations in beak shape are adaptations for harvesting particular food types such as small or large seeds
• Geospize fortis, smaller beak than geospize magniosris which has large beak
• In1982, G. magnirostris arrived, after the drought that occurred the beaks of larger birds were more frequent. In 1982, G. magnirostris arrived onto the island causing a competition for seeds between these two species. Geospize magnisotris were more likely to succeed since they are so much larger. In 2003 there was another drought, Which G.fortis did better?
• Now interspecific competition is occurring, smaller beaks did better, because they were not forced into competition with these guys.
• Competition changes what happens in terms of the evolution of traits
Standing or constitutive defenses
traits that allow individuals to avoid being eaten, and they are present even in the absence of predators
Animal always has capacity to always produce this, no change in morphology necessary
• Stotting: sometimes giseles start bouncing when cheetah (predator) nears. Energetically costly but it warns cheetah that giseles are powerful and fast. Stotting is an honest signal of quality. If they do not stot and simply run away, cheetah are not able to grab them.
• Aposematism: prey can warm predators that they are toxic through coloration.
• Prey may have weapons to help fight predators.
one species resembling another
ex. Batesian mimicry-natural selection favored mimic species that resembled the toxic species
only one of the two species is actually dangerous, the other one is just taking advantageous of looking like the actual dangerous one
• Ex king snake and coral snake. In areas where king and coral snakes live in close area. The apotopism in coral snakes are a warning and are known to be highly venomous. The scarlet king snake is a great mimic to coral snake.
• Alleles that allow birds to stay away from stuff like this is passed on, alleles that DO NOT die off (those birds got bitten by snakes and died).
ex. Mullerian mimicry-comimicry means neither will get eaten
both species are toxic or mistasteful to potential predators
• Ex: monarch butterflies in some parts of their range, cooccurr with a viceroy butterfly. They are extremely similar in morphology, and are both toxic. This helps prevent them from being bird prey. They sequester compounds like actemetophine in their bodies, and both of them are known to predators. Predators only need to learn one visual signal and both of these butterflies benefit from it.
• Each individual blue jay had been given a monarch butterfly and they ate it. They threw up, and after that they NEVER eat a monarch butterfly.
physical, chemical, or behavioral defensive traits that are induced in the prey in response to presence of predator.
efficient energetically, but slow
Are mussel defenses induced by the presence of crabs?
Hypothesis: mussels increase investment in defense in the presence of crabs
mussels downstream of the crab tank will have thicker shells than mussels downstream of the empty tank
-mussels do increase investment when they detect crabs. shell thickness is inducible
Why don't herbivores eat everything?
top down control hypothesis: herbivore populations are limited by predation and disease. predators and parasites remove herbivores that eat plants
bottom up: plant tissues offer poor nutrition and are well defended. Defense against herbivores such as capsasin, thorns, other toxic caompounds make plants not desirable to herbivores.
• In a series of islands, researchers removed predators from these islands and found that there were fewer plants. Herbivore numbers have increased and ate more of the plants. This supports that the top down hypothesis was supported.
eating your own species; ingestion of conspecific (same species) not heterospecific (=different species)
o Sexual Cannibalism: Female and male are copulating, while copulating, females eat male. Males are achieving reproductive success and offspring is getting energy. This only happens when males do not have a chance of finding another mate, so males allows this to occur. Selection favors this in an attempt to give nutrients to another offspring
o Tadpole: Cannibalistic morphs are able to recognize other siblings an make an effort not to kill their siblings
o Costs: potential for acquiring diseases is you eat members of your own species rather than if you eat non species . LOTS of parasites are species specific.
they made "playdough" snakes that looked like this toxic venomous snakes and put out models and looked to see how often they got attacked (y axis). Coral snakes decrease in abundance with increasing latitudes and elevation.
• Data supports prediction that: benefits of mimicry depend on abundance of model. At lower latitudes, birds are not attacking because there are coral snakes in the area and they know not to attack. If coral snakes go extinct, king snakes will be eaten. The model needs to continually being in the area...the king snakes rely on their being actual toxic coral snakes.
• They may have stingers or venemon, hunting in groups can allow for a predator to be taken down that they may otherwise not be able to do individually
• Deception: spider produces chemical that smells like a "moth" , they fly around and are looking for people to mate with. She latches around gets in contact with a male moth then eats him! She pretends to be a moth.
• Same sort of thing found indepp sea fish. When a smaller fish is moving by they take this lure and makes it look like food and puts it near little fish ,and whe they go to eat it they eat the fish!
• A male moth who ignores a mating female would never be able to reproduce, for the fish they would starve to death. They are selected to pay attention to this cues
o Predator adaptations: eavesdropping
• Tungara frog mating calls:
• Simple call: whine
• Complex call: whine + chuck
• Female frogs prefer the complex call, and the male species can produce either call. Predators also like the second type of call better, and can hear It better. Certain bats specialize in a certain species of frog. Mating signlals represent a trade off: predation vs mating success
predominant ecological niche on the planet
• The parasites live on the fish for years
• Nematodes in bird feces eaten by ants, nematode causes ants to hold it up in the air. Nematodes need to be eaten by birds to compelte life cycle. They manipulate ant (their host) to look like a berry so its life cycle can be complete (birds eat them)
Mutualism or Parasitism?
• Oxpecker traditional were thought to be cleaners, they eat ticks on large mammals. Researchers thought this was a story of mutualism, parasties get lost and oxpecker birds get food.
• Manipulation studies were done and they excluded oxpeckers from oxin and found that there was no effect on tick numbers but increased wounds! This tells you that the birds are parasites, they break the skin open and eat the blood of the mammal. Mammals do not like them, but have no choice cannot get them off!
Commensalism or Parasitism?
• Freshwater mussel= not clear whether its commensalism or parasitism .
• Only one fish on screen, piecies of freshwater mussels mimic fish. Larvae of musle need ot disperse upstream, and its hard ot do so they hitch a ride on the gills of a fish. The fish swim upstream and the larvae get dropped off. The lures have evolved. The fish don't suffer at all, they are simply dispersing. Commensalism is occurring.
o Commensalism or parasitism?
• Mites in eyelashes, and all over pores.
• We don't know if they are commensalism or paratism
How predictable are communities?
• Celements: advocated for one view point, that there there is stability within species interactions. All of those species interactions results in stable and predicatable communities.
• Gleason: advocated for opposite. You cannot predict what species are going to exist in an ecological community. After a disturbance, everything that ends up is all by chance..you cannot predict what it is! You cannot predict.
• 12 identical ponds were filled and sterilized at the same time. They identified each plankton species involved in each sample.
o Plankton got in pond from bird poop
• Data from this study: x axis shows total number of species, the y axis color coated name of each species in each pond.
• To a certain extent, each view point is supported. You cannot preict 100%, you can however predict some commonalitlies.
• Both hypotheses are partially correct
How do Keystone Species Structure Communities?
Keystone species whose structure can dramatically change an structure in the community they are found. The sea star
• Pisaster ochraceous is a sea star found
• Sea urchins and sea anenomes and crabs
• Whe n a keystone predator is present, they maintain diversity
• Ecological interconnectenss extremel important
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