Competition and Mutualism
Competition and Mutualism
Objective of Study
Understand different types of interspecific interactions:
Interspecific Competition: Competition between different species.
Mutualism: Positive interactions between species.
Commensalism: One species benefits while the other is unaffected.
Explore the effects of these interactions on species involved.
Investigate how competition results in species divergence and specialization.
Types of Species Interactions
Interspecific Competition: (- -)
Predation: (- +)
Parasitism: (- +)
Mutualism: (+ +)
Commensalism: (+ 0)
Interspecific Competition
Involves two or more species competing for a shared resource that is in limited supply.
Affects populations adversely; it reduces fitness for both competing species (denoted as (−, −)).
Both intraspecific and interspecific competition can occur simultaneously.
Example of Interspecific Competition
In N. American Eastern deciduous forests:
Resource: Acorns
Competitors: Gray squirrels, white-tailed deer, wild turkeys, etc.
Outcome: Species may start foraging for alternative foods when facing resource scarcity.
Forms of Interspecific Competition
Exploitation Competition: Indirect effect through resource use (depends on resource availability).
Interference Competition: Direct obstruction of access to resources (may not depend on resources).
Types of Exploitative Interactions
All interspecific interactions can be classified primarily into:
Consumption: One species inhibits another by consuming shared resources.
Preemption: One species prevents another from occupying a habitat (e.g. barnacles).
Overgrowth: One species grows over another, blocking access to resources.
Chemical Interaction: One species releases toxins or inhibitors affecting the other (e.g. allelopathy in plants).
Territorial: One species defends a territory and excludes others.
Encounter: Non-territorial interactions impacting species (e.g. scavengers competing for food).
Outcomes of Interspecific Competition
Exclusion: One species grows positively while the other negatively, leading to extinction of the latter.
Reverse Exclusion: The opposite outcome where species 1 goes extinct.
Coexistence: Both species inhibit their growth more than that of the other, leading to coexistence.
Competitive Dominance: One species inhibits the other more than its own growth, leading to dominance and potential extinction.
Competitive Exclusion Principle
States that two species that are complete competitors cannot coexist in the same environment indefinitely.
Conditions:
Constant environmental conditions.
Species require identical resources.
Can lead to resource partitioning, where species exploit portions of resources not accessible to others.
Resource Partitioning
Reduction of competition when species exploit different portions of a resource.
Often results from coevolution leading to distinct characteristics that minimize competition.
Example of Resource Partitioning: Warblers
Warblers reduce competitive overlap by exploiting different spatial or temporal aspects of the same resource.
Niche Differentiation
Coexisting species in a stable environment differentiate their niches (range of conditions under which species survive).
Competitive Release
Expansion of a species’ niche when a competitor is absent, leading to exploitation of new resources.
Character Displacement
Morphological, behavioral, or physiological shifts occurring due to niche partitioning which enables coexistence.
Interactions in Competition
Competition involves interactions shaped by numerous biotic (living) and abiotic (non-living) factors. Outcomes can vary based on environmental conditions.
Mutualisms Defined
Mutualism: A positive interaction benefiting both species involved.
Benefits include resource provision, protection from predators, reduction of competition, and enhanced reproduction.
Types of Mutualism
Obligate Mutualism: Both species cannot survive/reproduce without interaction.
Facultative Mutualism: Species can survive independently.
Levels of Specificity in Mutualism
Specialist Mutualists: One-to-one specific associations.
Generalist Mutualists: Interact with multiple species.
Examples of Mutualisms
Coral-Algae Relationship:
Corals obtain energy from symbiotic algae (zooxanthellae), while algae receive shelter and nutrients from corals.
Lichen: Fusion between fungus and algae/cyanobacteria.
Nonsymbiotic Mutualisms: Functionally dependent without physical coexistence (e.g., pollination, seed dispersal).
Defensive Mutualisms
Ants protecting Acacia trees, benefiting from food and shelter provided while attacking herbivores.
Cleaning mutualisms involving fish and shrimp removing parasites from larger fish.
Pollination and Seed Dispersal Mutualisms
Pollination leads to plant fertilization through animal pollinators.
Seed dispersal involves animals helping plant reproduction by carrying seeds to new locations.
New section
Objective of Study
Understand different types of interactions between species:
Interspecific Competition: Competition between different species.
Mutualism: Positive interactions that benefit both species.
Commensalism: One species benefits while the other is not affected.
Explore how these interactions affect the species involved.
Investigate how competition can lead to species changing and specializing.
Types of Species Interactions
Interspecific Competition: (- -)
Predation: (- +)
Parasitism: (- +)
Mutualism: (+ +)
Commensalism: (+ 0)
Interspecific Competition
This occurs when two or more species compete for limited resources.
It can hurt both species involved, reducing their survival.
Competition can happen both within a species (intraspecific) and between different species (interspecific).
Example of Interspecific Competition
In North American Eastern forests:
Resource: Acorns
Competitors: Gray squirrels, white-tailed deer, wild turkeys, etc.
Outcome: Species may foraging for different foods when supplies are low.
Forms of Interspecific Competition
Exploitation Competition: One species uses resources, limiting what is available for others.
Interference Competition: One species directly blocks access to resources for another.
Types of Exploitative Interactions
Consumption: One species eats another.
Preemption: One species takes up space, preventing another from occupying it (like barnacles).
Overgrowth: One species grows over another, blocking resources.
Chemical Interaction: One species releases chemicals that harm another (e.g., plants releasing toxins).
Territorial: One species defends an area to exclude others.
Encounter: Non-territorial interactions that impact species (e.g., scavengers competing for food).
Outcomes of Interspecific Competition
Exclusion: One species thrives while the other goes extinct.
Reverse Exclusion: The opposite outcome happens, with the first species going extinct.
Coexistence: Both species limit each other's growth but can coexist.
Competitive Dominance: One species is stronger, which could lead to extinction of the weaker one.
Competitive Exclusion Principle
States that two species that compete completely cannot coexist indefinitely in the same environment.
Key conditions:
Consistent environmental conditions.
Identical resource needs.
This can lead to resource partitioning, where species use different parts of a resource.
Resource Partitioning
This is when species reduce competition by using different parts of a resource.
It often results from evolution that leads to differences in their characteristics.
Example of Resource Partitioning: Warblers
Warblers reduce competition by using different areas or times to access the same resource.
Niche Differentiation
Species in a stable environment develop distinct niches (specific conditions where they live).
Competitive Release
This happens when a species expands its niche in the absence of a competitor, accessing new resources.
Character Displacement
Changes in physical traits, behavior, or physiology occur due to niche separation, helping species coexist.
Interactions in Competition
Competition is influenced by many living (biotic) and non-living (abiotic) factors, and results can change based on the environment.
Mutualisms Defined
Mutualism: A beneficial interaction for both species.
Benefits include sharing resources, protection from predators, reducing competition, and aiding reproduction.
Types of Mutualism
Specialist Mutualists: Specific one-to-one relationships.
Obligate Mutualism: Both species depend on each other to survive.
Symbiotic is the close interaction between two different organisms, which may be beneficial, neutral, or harmful. The main types include:
Mutualism: Both species benefit (e.g., bees and flowers).
Commensalism: One species benefits, and the other is unaffected (e.g., barnacles on whales).
Parasitism: One species benefits at the expense of the other (e.g., ticks on mammals)
Generalist Mutualists: Interact with many species.
Non-symbiotic relationships involve interactions between organisms without close physical contact or dependency. Common types include:
Competition: Different species compete for the same resources.
Predation: One organism (predator) hunts another (prey).
Facultative mutualism occurs when two species benefit from each other, but the relationship is not essential for their survival; which can involve specialist and generalist mutualists.
Examples of Mutualisms
Coral-Algae Relationship: Corals gain energy from algae, while algae receive shelter and nutrients.
Lichen: Combination of fungus and algae/cyanobacteria.
Non-symbiotic Mutualisms: Functionally dependent without physical contact (like pollination transfer to flowering plants and seed planting from animals dropping fruit seeds).
Defensive Mutualisms
Involve interactions where one species provides protection or defense to another in exchange for benefits such as food or shelter.
Ants protect Acacia trees in return for food and shelter, while attacking herbivores.
Cleaning mutualisms where fish and shrimp remove parasites from larger fish.
Mutualisms: Seed Dispersal
Seed dispersal involves animals carrying seeds to different locations for plant reproduction.