Ecology and Species Interactions

Species Interactions

• Species Interactions

  • Category of ecological study addressing how different species affect each other.

  • Types of interactions:

  • Inter-specific: interactions between different species

    • Examples: competition, predation, herbivory, symbiosis

    • Affects survival and reproduction, can have positive (+), negative (-), or neutral (0) outcomes

  • Intra-specific: interactions among same species

Key Concepts in Ecology

• All Life is Interconnected

  • Important factors to consider:

  • Major types of species interactions

  • Major characteristics defining communities

• Important Considerations:

  • Yellowstone Wolves: Top-down influences on community dynamics

  • Photuris Fireflies: Adaptations to evade spider predation

  • Resource Partitioning in Balanus and Chthamalus to reduce competition

• Understanding:

  • Species interactions drive evolutionary adaptations

  • Disturbance alters community structures

  • Human impacts acting as predators in ecosystems

Levels of Organization in Ecology

• 6 Levels:

  1. Global ecology

  2. Landscape ecology

  3. Ecosystem ecology

  4. Community ecology

  5. Population ecology

  6. Organismal ecology

Concept of Ecological Community

• Defined as:

  • All species inhabiting the same area

Competition (-/-)

• Defined as:

  • Species competing for limited resources

  • Outcomes:

  • Competitive Exclusion Principle: Two species occupying identical ecological niches cannot coexist

  • Ecological niche: the role and space an organism occupies in an ecosystem

Examples of Competition (-/-)

• Example 1: Charr and Cisco Fish

  • Charr eliminated from an ecosystem due to intense competition with Cisco

  • Cisco identified as the superior competitor

  • Observational study of stomach contents to analyze dietary overlap and competitive dynamics

• Example 2: Barnacles

  • Experiment conducted by removing Balanus species leading to the realization of Chthamalus species distribution patterns

  • Competitive dynamics affected by tidal zones indicating fundamental vs realized niches

Ecological Niche

• Fundamental Niche:

  • Niche that a species could potentially occupy if no other species were present

  • Defined by physical and chemical conditions for survival

• Realized Niche:

  • The actual niche occupied by a species reflecting biotic interactions

  • Includes constraints from interactions with other species

• Comparison of both niches demonstrates how abiotic factors inform limits while biotic relationships shape community structure

Resource Partitioning

• Definition:

  • When ecologically similar species coexist due to slight differences in their niches

• Example: Warblers

  • Various species partitioning resources by differing feeding zone preferences

• Example: Bluegill and Green Sunfish

  • Bluegill under food resource partitioning adjust to feeding on plankton, leading to reduced growth

  • Green Sunfish identified as superior competitor in littoral zones

• Research on Bats:

  • Study on resource partitioning between Indiana and little brown bats highlighting location and habitat preferences

Types of Species Interactions

Predation (+/-)

• Definition:

  • Interaction where predator kills and consumes prey

  • Predators adapt via physical traits such as claws and poison

• Prey Defenses:

  • Behavioral: fleeing, forming herds

  • Morphological: coloration for camouflage, toxins

• Mimicry:

  • Batesian Mimicry: Non-toxic species resemble toxic species

  • Example: Viceroy butterfly mimicking Monarch

  • Müllerian Mimicry: Different toxic species evolve similar warning signals; mutual benefit

  • Example: Various poisonous frog species developing similar color schemes

Herbivory (+/-)

• Definition:

  • Herbivore consuming plants or algae, leading to plant adaptations such as chemical defenses

• Plant Responses:

  • Production of secondary metabolites to deter herbivores

  • Example: Volicitin attracting predatory wasps to counteract herbivory effects

Symbiosis

• Total:

  • Interactions where two or more species coexist closely

  • Types:

  1. Parasitism (+/-):

     • One organism benefits at the expense of another (host)

     • Types: Endoparasites (internal) and Ectoparasites (external)

  2. Mutualism (+/+):

     • Both organisms benefit; can lead to co-evolution

     • Example: Ants defending Acacia trees while receiving shelter

  3. Commensalism (+/0):

     • One species benefits while the other remains unaffected; often challenging to observe due to interdependence inherent in ecosystems

Community Characterization: Diversity and Trophic Structure

Species Diversity

• Defined as the variety of organisms in a community

• Components:

  • Species Richness: Number of different species

  • Relative Abundance: Proportion of each species within a community

Importance of Diversity

• Higher diversity leads to:

  • Increased community productivity and stability

  • Improved resilience to environmental stress

  • Enhanced resistance to invasive species

Trophic Structure

• Definition:

  • Feeding relationships within a community

• Food Chains & Webs:

  • Food chains link trophic levels from producers to top carnivores

  • Food webs represent complex interactions between various feeding relationships

Trophic Cascade

• Ecosystem dynamics governed by predators through indirect interactions

• Predator presence affects herbivore populations and consequently primary producers through:

  • Direct negative interaction (predator to herbivore)

  • Indirect positive interaction (herbivore to primary producer)

Ecological Succession

• The predictable change within communities over time

  • Primary Succession: Occurs in lifeless environments leading to the development of a community

  • Disturbance resets ecological cycles and can result in changes across community structures

• Stages include:

  • Pioneer Species

  • Intermediate Species

  • Climax Community