Why are there so many different kinds of organisms? How do species interact with one another to make stable Ecological Communities?

Why are there so many different kinds of organisms?

How do species interact with one another to make stable

Ecological Communities?

Ecological Effects of Species 1 onSpecies 2:

(A) Effect is Positive (+) if species 1 increases the numbers of species 2.

(B) Effect is Negative (-) if species 1 decreases the numbers of species 2.

Ecological Effects of

One species on the other

Species 2

+ -

Species 1+ Mutualism Predation

- Predation Competition

Ecological Effects of

One species on the other

Species 2

+ -

Species 1+ Mutualism Predation

- Predation Competition

Mutualism is an interaction between two (or more) species that is

beneficial to both (all) species.

Mutualism is an interaction between two (or more) species that is beneficial to both (all) species.

Algae: + effects on fungi, photosynthesis produces nutrientsfor the fungus.

Fungus: + effects on algae, provides nutrition and some chemical defenses.

Lichens: Mutualism between fungus, cyanobacterium and algae> 13,500 species of lichens

"Ambrosia" Beetles Scolytidae feed on fungi growing in galleries

Beetlescarry fungalspores and

keep galleriesat optimal

humidity for fungal growth

Xyleborus dispar: feeds on fungi growing in galleries

Mutualism is an interaction between two (or more) species that is beneficial to both (all) species.

Beetles: + effects on fungi, ‘plant’ the fungal sporesand maintain optimal humidity for fungal growth.

Fungus: + effects on beetle, provides nutrition and some chemical defenses.

Ant-Acacia Mutualism

Acacia Tree: provides shelter and food for the ants

The Ants: provide protection against fire, caterpillars and herbivorous mammals for tree.

Acacia Tree provides nectar and protein and hollow thorns for ant colony.

Ant-Aphid mutualism

Ant: protects aphid from predators.

Aphid: provides plant sugars for the ants

Ecological Effects of

One species on the other

Species 2

+ -

Species 1+ Mutualism Predation

- Predation Competition

Competition occurs when of two species each require the same limited resource. The availability of the resource to one species is negatively influenced by the presence of the other species. It is a "-/-" interaction.

Gause’s Competitive Exclusion Principle:When two species make similar demands

on a limited resource, then one or the other species will go extinct as a result of

competition for the resource.

Paramecium caudatum

Paramecium aurelia

Single Species Populations

Competition Populations

Gause’s Experiments

Competition occurs when of two species each require the same limited resource. The availability of the resource to one species is negatively influenced by the presence of the other species. It is a "-/-" interaction.

Triboliumconfusum

Triboliumcastaneum

Thomas Park’s experiments

Single Species Equilibrium Population Size when reared ALONE Predict the

Winner in

CompetitionClimate T. castaneum T. confusum

Cold-Dry 21 208

Cold-Wet 99 225

Warm-Dry 150 237

Warm-Wet 401 264

Hot-Dry 77 190

Hot-Wet 306 329

Single Species Equilibrium Population Size Predict the

Winner in

CompetitionClimate T. castaneum T. confusum

Cold-Dry 21 208 confusum

Cold-Wet 99 225 confusum

Warm-Dry 150 237 confusum

Warm-Wet 401 264 castaneum

Hot-Dry 77 190 confusum

Hot-Wet 306 329 Toss Up

Competitive Outcomes: Percent WinsPredicted

Winner in

CompetitionClimate T. castaneum T. confusum

Cold-Dry 0% 100% confusum

Cold-Wet 30% 70% confusum

Warm-Dry 13% 87% confusum

Warm-Wet 86% 14% castaneum

Hot-Dry 10% 90% confusum

Hot-Wet 100% 0% Toss Up

Competitive Outcomes: Percent WinsPredicted

Winner in

CompetitionClimate T. castaneum T. confusum

Cold-Dry 0% 100% confusum

Cold-Wet 30% 70% confusum

Warm-Dry 13% 87% confusum

Warm-Wet 86% 14% castaneum

Hot-Dry 10% 90% confusum

Hot-Wet 100% 0% Toss Up

Unusual Outcomes based on Single Species Population Size

Gause’s Competitive Exclusion Principle:When two species make similar demands

on a limited resource, then one or the other species will go extinct as a result of

competition for the resource.

One species won and the other went extinct in every one of the 170

Tribolium competition populations

Changing the Climate from Hot-Wet to Cold-Dry

Changed the identity of the winning species from T. castaneum to T. confusum.

Stochastic Outcome: In Intermediate Climateseach species won in at

least some of the competition populations.The outcome of competition is not completely

Predictable.

Interactions of More than Two Species

T. Castaneum vs T. confusum: -, - interaction = Competition

Hot-Wet: T. castaneum wins 100%

Cold-Dry: T. confusum wins 100%

Change Environment by ADDING a pathogenAdelina tribolii: protozoan pathogen of beetles

T. castaneum vs T. confusum with Adelina tribolii:Hot-Wet: T. confusum wins 80%

Changing the Environment by ADDING the pathogen

Adelina triboliiChanged the identity of the winning species

from 100% T. castaneum to 80% T. confusum.

Stochastic Outcome: In Intermediate Climateseach species won in at

least some of the competition populations.The outcome of competition is not completely

Predictable.

Interactions of More than Two Species

Ant-Aphid-Tree: Pairwise Interactions: Ant-Aphid: +, + interaction = mutualism Aphid-Tree: +, - interaction = herbivory

Caterpillar-Tree: + , - interaction = herbivoryCaterpillar-Aphid: 0 , 0 interaction

Four-Way InteractionAnt-Aphid-Tree: +, +, + since ants remove

caterpillars which have a larger negative impact on tree. Caterpillars: removed from system by ants.