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 on Species 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 + MutualismPredation - Competition

Ecological Effects of One species on the other Species 2 +- Species 1 + MutualismPredation - 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 nutrients for 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 Beetles carry fungal spores and keep galleries at 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 spores and 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 + MutualismPredation - 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.

Gauses 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 Gauses 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. Tribolium confusum Tribolium castaneum Thomas Parks experiments

Single Species Equilibrium Population Size when reared ALONE Predict the Winner in Competition Climate T. castaneumT. confusum Cold-Dry Cold-Wet Warm-Dry Warm-Wet Hot-Dry Hot-Wet

Single Species Equilibrium Population Size Predict the Winner in Competition Climate T. castaneumT. confusum Cold-Dry confusum Cold-Wet confusum Warm-Dry confusum Warm-Wet castaneum Hot-Dry confusum Hot-Wet Toss Up

Competitive Outcomes: Percent Wins Predicted Winner in Competition Climate T. castaneumT. 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 Wins Predicted Winner in Competition Climate T. castaneumT. 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

Gauses 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 Climates each 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 pathogen Adelina 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 tribolii Changed the identity of the winning species from 100% T. castaneum to 80% T. confusum. Stochastic Outcome: In Intermediate Climates each 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 = herbivory Caterpillar-Aphid: 0, 0 interaction Four-Way Interaction Ant-Aphid-Tree: +, +, + since ants remove caterpillars which have a larger negative impact on tree. Caterpillars: removed from system by ants.