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Community : Interactions

THE REALM OF Ecology ECOLOGY Biosphere Community: All the populations of organisms • Biosphere living together in a given • place • Community Ecology: Characteristics: Interactions among Communities members of all of the • in a given – . – Relative

Populations • Dominant vegetation • Stability/ Organisms Redwood forest community

The Niche Concept Why do species Y & Z coexist? • A population’s Habitat is the area in which it lives - “address” • Individualistic Hypothesis • Niche is a population’s total use of biotic and abiotic resources - “profession” – Y & Z need similar physical environment • Interactive Hypothesis • Multiple species within a community share habitat, but have different niches – Y needs Z – The competitive exclusion principle states that two species competing for the same limiting resources cannot coexist in the same place

Community Ecology Interspecific Interactions Interactions among Y Z members of all – – of the species in a given habitat. + – trophic — parasites / predators + o / facillitation A. Competitive Interactions B. Trophic Interactions Direct + + interactions C. Symbiotic Interactions o – amensalism D. Amensal Interactions Indirect interactions E. Facilitative Interactions

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A. Competition Example of Competitive Exclusion • Two barnacle populations require • Interspecific the same : Competition = when space two species compete • When Balanus is Species A Species B removed for the same limited Chthamalus resource spreads lower • Competitive – Fundemental niche Exclusion = the • When both species elimination of a compete Balanus displaces population due to Species A & B Barnacle populations illustrating Chthamalus competition Gause’s experiment w/ Paramecium competitive exclusion – Realized niche

A. insolitus usually perches • in on shady branches. Anolis

A. ricordii A. ricordii

A. insolitus

A. alinigar A. christophei A. distichus A. cybotes • in A. cybotes A. etheridgei A. etheridgei shorebirds

A. distichus perches on fence posts and other sunny surfaces. Figure 53.3

Competition & B. Trophic Quaternary consumers Character Displacement (Feeding) • Geospiza spp. on islands of the Galapagos Carnivore Interactions Tertiary – allopatry 60 Los Hermanos consumers – sympatry 40 G. fuliginosa, Carnivore Carnivore 20 allopatric

0 Secondary consumers 60 Daphne Carnivore 40 Carnivore G. fortis, 20 allopatric 0 Primary consumers 60 Santa María, San Cristóbal Sympatric populations Zooplankton 40 20 Primary 0 producers 8 10 12 14 16

Percentages of individuals in each size class Beak depth (mm) Phytoplankton Figure 54.11 A terrestrial A marine food chain

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Primary producers • (“self feeder”) – Photosynthetic , protists, – Chemoautotrophic bacteria • Obtain nutrients from nonliving materials – Inorganic compounds, minerals

– CO2 to make organic backbones – Carbon fixation

Decomposition is an important Consumers part of an ecosystem • (“feed on others”) • ( = decaying matter)  Another level – (“plant eater”) of • Primary consumers: eat producers  Recycle – (“meat eater”) matter back into the • Secondary consumers: eat other abiotic world consumers

Biomagnification A • Efficiency of transfer • Trophic patterns creates a food are rarely linear pyramid. • Typically ~10% [5– • Pyramid effect may 20%] efficiency of result in transfer between levels of • I.e., to grow or environmental reproduce, 10x the contaminants. added energy & mass – Esp., compounds must be consumed. sequestered in fat or • Thus there must be a skeleton. lot of to support long food chains.

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+ – and • Mechanisms of defense have evolved in every species (size, flee, hide, venom) • = a series of reciprocal adaptations in two species (a type of “arms race”)

Coevolution: caterpillar and passionflower vine

• Herbivory – One species (herbivore) eats part of a producer (prey)

• Predation

• Specialist herbivores acquire resistance to chemical – One species (predator) kills & defense of specific prey consumes another species (prey)

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+ – + –

Cryptic Coloration () Physical (Mechanical) defenses – Spines, bristles, shells • Repels predator • Makes hard to swallow/digest • Makes it too energetically expensive porcupine  Works for both predator and prey – Cost > benefit for the predator

Chemical defenses Sometimes defenses don’t work! • Chemical warfare – Predator learns to avoid species – Examples • Eucalyptus oil, oleander shrubs, stinkbugs, skunks, cane toads • mouse sticks stinky end into Stink ground to munch head

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Mimicry • Color and patterns of warning coloration are copied

(a) Cuckoo

(b) Yellow jacket Figure 53.8 poison dart • In Müllerian , multiple noxious or unpalatable species resemble each other.

Mimicry Mimicry • Color and patterns of warning coloration are copied • Color and patterns of warning coloration are copied

Fly Stingless Wasp anterior end of a snake

Yellow Beetle Jacket posterior end of a hawkmoth caterpillar

• In , harmless species • In Batesian mimicry, harmless species mimic dangerous or toxic species. mimic dangerous or toxic species.

Mimicry Mimicry • Color and patterns of warning coloration are copied • In Batesian mimicry, harmless species mimic dangerous or toxic species. • Only works if predators learn to avoid real danger!

venomous coral snake

non-venomous king snake • In Batesian mimicry, harmless species

mimic dangerous or toxic species. Figs. 1.25–1.27

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Figure 54.6

Mimic + – master of Batesian mimicry (a) Mimicking a venomous snake • Rapidly changes coloration, morphology & behavior

(b) Mimicking (c) Mimicking a poisonous a stingray https://www.youtube.com/watch?v=t-LTWFnGmeg

Predation and Diversity Predation and Diversity

• Keystone Predator • Keystone Predator = a species that = a species that reduces the reduces the population density population density of the strongest of the strongest competitors Pisaster sea star eating a mussel competitors Pisaster sea star eating a mussel • Predation can • Predation can help maintain help maintain species diversity

C. • Partivory – One species (partivore) consumes part of another • Sym- : “together”; -bios: “living” species () without killing or consuming all of it • One species living in, or on, or in tight association with another species • Symbiont and Host • Three types of symbiosis – + – – Commensalism + o – Mutualism + +

Aedes aegypti feeding on human

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+ – Parasitism

Parasitism • Symbiont benefits at the expense of the host • Symbiont benefits at the expense of the host • Other kinds of parasite cost their host something else • E.g., “”: Cuckoo “foster” their young in other • Trophic parasite feeds off tissues of host (partivore) species nests – Ectoparasites & Endoparasites – Not all partivores are parasites (symbionts)!

tick

+ o Commensalism • Parasite or slow predator? – A “good” parasite does not kill its host • Parasitoid wasp stings & paralyzes — but does not kill it • Lays eggs inside spider • Wasp larvae hatch & consume living spider • Spider killed when metamorphose & emerge

Eagles nesting in conifers • Symbiont has no significant effect on host

+ + + o? Mutualism Both symbiont & host benefit from the relationship

Acacias & • Manta & remoras

S. Am. Acacias provide shelter, nectar & antfood to harbor Pseudomyrmex ants • Is the effect of the symbiont on the host Ants defend the acacias from herbivores, really insignificant? pathogenic fungi, & competing vegetation

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+ + Amensalism: Endosymbiotic A species is neither benefited nor harmed by another species, but the activity, metabolism or defenses of the Mutualism first species inhibits or eliminates the second species Harmful algal blooms (HAB) Termites & • Overgrowth of photosynthetic or protists Corals & Trichonympha • Consumption of dO2, decreased light penetration, and/or Symbiodinium production of toxic metabolites impacts other aquatic spp. [Zooxanthellae]

Amensalism: Competition or Amensalism? A species is neither benefited nor harmed by another species, but the activity, metabolism or defenses of the first species inhibits or eliminates the second species • If Balanus distribution is the Human amensalism same whether or not • Agricultural & urban development, and waste production Chthalamus is present, should it be • Negatively impact many species called a competitive or amensal interaction? Burrowing owls • Inhabit old tunnels of prairie or ground squirrels in dry grasslands • Populations nation-wide threatened by habitat loss • Listed as endangered & CA Species Barnacle populations illustrating of Special Interest competitive exclusion

Pathogens Facilitation • that cause disease • Growth of turf  slows water flow rate  • May be trophic or amensal enhanced by seeds

– Sudden Oak Death (SOD)

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