Download Chapter 25 Communicaton Ecology 25.1 INTERACTIONS AMONG

Chapter 25 Communicaton Ecology
25.1 INTERACTIONS AMONG COMPETING SPECIES SHAPE ECOLOGICAL NICHES
I. The Realized Niche
A. niche:sum totalfood, temp. range, area that organ. occupies/pattern of living Habitat: where it lives
Interspecifc Competition: 2 species try to use same resource but not enough for both
Interference Competition: Fighting over resources Exploitative Competion: Sharing Resources
Fundamental Niche:Organ. niche that it is physicall possible to occupy
Realized Niche: It's acual occupied niche, be it limited by competition or something else
B. J.H. Connels Scotland studay of the barnacle Chthamalus Stellatus and Semibalanus Balanoides showed that
C.Stellatus' fundamental niche was both deep and shalllow water, but it's realized niche was shallow water due
to it being outcompeted by S. Balanoides. Further, S. Balanoides realized and fundamental niche was deep water
because it could not survive in the shallow
C. Predators can limit realized niche (i.e. St. John's Wort by beatle)
D. Absence of another spc. limite realized niche (i.e. plants depend on honeybee for pollunation)
II .Gause and the Principle of Competitve Exclusion
A. princiiple of competitive exclusion shows 2 spcs. can't coexsist with limited resources. Paramecium P.
aurelia, growing 6 times faster than P.cadatum showed G.F. gause this
B. Niche Overlap
(1) P.Caudatum and P.burasria having fundamental niches of the whole tube but having realized niches of top and
bottom of the tube respectively showed Gause overlap.
(2) There was still a negative effect as each spc weren't as dense as if grown seperately
C.Competitve Exclusion
(1)Restated princile: No two species can occupy the same niche idefinitely when resoucres are lmitied
(2)Coexisting spcs either have abundant resoucres or are physically diff. otherwise competitve exclusion
occurs
III. Resource Partitioning
A. Robert MacArthur's study of 5 warblers coexisting seemed to condradict C.E. principal. Found that they subdivied
the niche, feeding on different parts of the spruce tree, to avoid direct compettion with one another
B. Occurs more often in sympatric species, thought to result from Natural Selection
C. Thus Character displacement or differences in Morphology (form and structure of organ.) occurs more in
close sympatric species compared to allopatric species
IV.Detecting Interspecific Competition
A. 1 spc's thriving and the other dying doesn't necessary mean C.E.--could be 1 likes warm conditions/1 doesn't
B. Experimental Studies of Competition
(1) Field studies best for showing evidence
(2) Chihuahuahn Desert Rodent would survive better in enclosures without Kangaroo rat compared to those with
(3) Pop. size not only effect of C.E.-- behavior and growth can be accounted i.e. A.Gingivinus Anolis lizard grow
faster/bigger when bred alone
C. Caution Is Necessary
(1) Neg. effects on one spc, don't nec. mean C.E.. experiments must be combined with study onecological
mechanism causing negative effect
a).adult's of one spc of fish will prey on another spc, causeing negative effect
b). one spc. will attract pred. that will prey on the other spc
(2) Experiments not always feasible, (i.e. grey wolf to large/numerous to handle, trees row too slowler) only
alternative is studies of ecological requirements of the speicies
25.2 PREDATORS AND THEIR PREY COEVOLVE
A. Predation cannot exist without refuges for prey, in order for predator levels to drop and a recovery for the
prey population
I. Predation and Prey Populations
(1) Introduction or Removal of Pred. into/out of pop. by humans can haev large efects on prey pop. (Exampls, sea
otter removal-->sea urchin explosion, rats in--->galapagos tortoises die, prickly pear dominates, actolastis
Cactorum moth Introduced as natural predator to lower levels
B. Predation and Evolution
(1) Ongoing arms race btw pred. and prey--adaptions by prey to avoid capture followed by counterapadtion by
pred.
a).During Mesozoic, crustaceans evolved to open mollusk shell, mollusk countered with hard shells, spines
Defence Mechanisms in Plants and Animals
I. Plants Defense against Herbivores
A. Morphological defenses i.e. spine, prickes, silica in cells make them too tough to eat
B. Chemical Defenses primary compounds used for metaboli pathways (i.e. respiration), secondary chemical
compountds structurally differnt to disturb metalbolism of herbivores
(1) Mustard family (cabbages, radish etc)/milkweed/dogane have mustard oils toxic substances and sumtimes
cardiac glycosides that have big effect on hearts of vertbrates
C.The Evoluationary Response of Herbivores
(1)Cabbage butterfly and monarah butterfly catapillars can feed on th mustard family and milkweed and dogband
families because they evoloved to ability to break d9own mustard oils. they also have sense organs to detect
their specific feedign spcs, isolating that spc food just to themselves
(2) ^^^^Serves as an example of Coevolution
II.Animal Defenses against Predators
A. Monarch Catpillars who eat milkweed family plants store the cardiac glycosdies in fat bodies so through each life
cylce, they are protected from birds who can't handle the glyco's. These butterflys are orange and black
(1) Somebirds haev evolved the ability to toelerate and do eat the butterflys
B. Defensive Coloration
(1)Warning Coloration/Aposematic Coloration: Bright Colored's signify poisions and stings, repel preds.
(2)Cyrptic Coloration: camoflague, groups of this type don't exist cuz 1 giveaway would giveaway all
C. Chemical Defenses bugs, sciporion etc use chemicals to defend and kill their prey, marine algea can fight cancer
,used for antibiotics
III.Mimicry
A. Batesian Mimicry
(1) When non-toxic spc resemeber toxic ones, in hopes to fool predators
a).toxic model butterfly eat select toxic plants to then incorporate into body, the mimicry eats variety of
plants, non-toxic but still fools preds
B.Mullerian Mimicry
(1). Groups of protected spc, look like one another/group defense so that the pred. learns quiclky to avoid
C.Behavior must be mimiced also in order to fool preds.
25.3 EVOLUTION SOMETIMES FOSTERS COOPERATION
I. Coevoluion and Symbiosis A. Coevolution organs. evolve to one another i.e. plant/bee adapting for dispersal/food procuring
B. Symbiosis is Widespread
(1). another type a coevolotion Organism that live together devlp. symbiotic relationships
a).Lichens and Mycorrhizae with tres help metabolic processes
b).Leafcutter ants bring leaves to underground fungi, which in turn make food for ants
C. Kinds of Symbiosios
1).Commensalism: one spc benefits, nother happends to other 2). Mutualism: Both Benefit
3).Parasitism: One benefits, the other is harmed, diff from predation cuz harmed org. doesn't nec. die
II. Commensalism
A. often occurs as 1 spc. is to attached to the ohter
B. Examples of Commensalism
(1) Barnacles on whales, Gain: potection from predation, gamete dispersal, <water circulation for filter feeders
(2) Clownfish living in sea anemones that would paralyze others Gain: protection, ditritus food source left by S.A.
(3) Oxpecker birds on grazing animals gain, birds pick of pararsites and other insects
C. When is Commensalism Commensalism
(1) Mutualism? May be advantages for S.A's to haveditritus pick from tentacles, & ^birds have perm. food source
(2) Parasitism? oxpeckers pick off scabs and drink blood weakening animal
III. Mutualism
A. Reltionship btw animals and flowers for disperal/food have become greatly specailsized
B. Ants carry aphids to trees, cuz ants consume leftover excreted surcrose of the aphid
C. Ants and Acacias
Ants of genus Pseudomyrmex in Latin America live in stipules of Acacia where they feed off Beltian Bodies
(special organs made just for them) and sugar-rich nectar. In return, the ants fight of predators, clear
away other plants whenever it blocks the host plans light and toghether with brought in organinc materal and
their excretion the ants provide the plant ith a source of nitrogen
D. A simliar species in africa, crematogsater nigriceps, lives in acacia, but cuts off branches of it's host plant to
prevent invasion by other ants and thus sterlizng acadia and becoming a parasitic interaction
IV. Parasiism
Parasie is usully much smaller than the prey and hard to distinguish btw other symbiosis
A. External Parasites/ectoparasites live outside, lice, not mosquitos (because of brief interaction)
(1) Parasitoids, lay eggs in lvining host, i.e. wasps
B. Internal Parasites/endoparasites: live inside host, not bacteria viruses
(1)much more specialed, the more specialed the life of parasite ties in, the more it has evolved to fit it's host
C.Brood Parasitism: Cowbirds, cuckoo's lay eggs in other birds nest while host bird rasises young like it's own
V. Interactions Amoun Ecological Processes
A. In nature <1 type of interaction can occur at a given time, with some reversing another type
B. Predation Redcues Competion
(1) spc A may outcompete spc B but preds will go after the more abundant one, thus cancelling effects of C.E.
a).Starfish eat bivalves control pop. size, when starfish removed, bivalves outcompete everyone, explode
C.Parasitism May Counter Competition
(1) The flower beatleTribolium Castanerm survies without parasite present while, T.confusum surevies with it
(2) A usually competitively inferious spc of nolis lizard is immune to malaria, when malaria is present, it thrives
D.Indirect Effects
(1) Rodents in the Chihuahuan Desert typically outcompete rats for seeds, however when rodents are removed
the ants populations don't explode as expected but decline. This is becuase the large seed plants that rodents
usually eat, outcompete the small seeds that the rats eat in absense of the rodents, thus elimating rat food supply
E. Keystone Species
(1).^Orgns. with strong effect on compostion of communities (i.e. starfish in above example)
b).beavers making dams, create new habitats
c).alligators holes at bottom of lakes provide h20 for other animals during drought
25.4 ECOLOGICAL SUCCESSION MAY INCREASE SPECIES RICHNESS
I. Sucession-ecosystems changing from simple to complex even if climate remains stable
A. Secondary Sucession: example of cleared woods becoming a forest again over time
B. Primary sucession
(1) Occur of bare substrances-retreated glaciers, volcanic island rising above sea
(2)Example of sucession of glacial moraines: lichens firsh grow on mineral poor soil making pockets of good soil,
then moses get to the pockets adding to the soil for alder shrubs, untilll over 100's years N
2 levels rise enough for a
spruce forest.
(3) At the same time an oligotrophic(nutrient poor) lake becomes eutrophic (rich in nutrients) spc richness wil
grow and then decline
(4) Cuz all sucesion leads to similar vegation in the entire are, Clements suggest idea of climax community,
the final constant stage of sucession
a).^idea rejected because 1).climate keeps changing 2)slow process of sucession 3)humans effect
vegation too much
C. Sucession Happens cuz spc alter habitat that also favor other spcs
1).Tolerance, early stages hae weedy r-selecte spc that can tolerate harsh condition
2).Facilition: Glacier Bay mosses facilitate soil adding N2 for the alders who do the same for the spruce
3).Inhibition: precursor spc can't grow in facilitate enviro i.e. alders can't grow in the new spruce forest
D. Spc richness rises an declines cuz it's baren so nat. spc come in but eventually specialed k-select spc picked
outcompeting others
II. The Role of Disturbance
A. Disturbances can cause enviro. to revert stages back in sucession or even all the way back to start
(1).forest fires, drought, floods, gypsy moths consuming all dreers, unregulated deer grazing
B. Intermediate Disturbance Hypothesis
(1)Communties with moderate amounts of disturbance will have <spc richness why?
a).pockets of different enviroments will have pockets of different spc relateing to that episode in sucesion
b).disturbance prevents reaching final stage in while specialized species outcompete others >spc richness
(2) Scientis accepting disturbance as norm rather than exception