prey adaptation bsci

Three-Dimensional Niche Hypervolume

  • Organisms operate within a three-dimensional niche hypervolume, defined by the dimensions relevant to their survival and reproduction.
    • Dimensions considered include:
    • Temperature (increasing and decreasing)
    • pH (increasing and decreasing)
    • Light (increasing and decreasing)
  • This hypervolume consists of different parts that are more or less suitable for particular species based on these dimensions.

Simplifying Niche Concepts

  • One-dimensional and two-dimensional niches are easier to conceptualize.
  • Temperature alone is often a critical factor in species segregation due to tolerance limits.

Case Study: Barnacles on the Pacific Coast

  • Examined barnacle species, specifically brown barnacles and blue barnacles.
    • Brown barnacles: higher on the rock face.
    • Blue barnacles: lower on the rock face.
  • Research Focus: Understand spatial distribution and the effects of competition.

Experimental Design and Results

  • Researchers experimented by:
    • Removing blue barnacles from certain rock faces and observing effects on brown barnacle distribution.
    • Removing brown barnacles to see if blue barnacles could then extend higher on the rock face.
  • Findings:
    • Blue barnacles maintained their low position regardless of brown barnacle presence.
    • Brown barnacles expanded their range downward when blue barnacles were removed, indicating they were out-competed.
    • Blue barnacles did not occupy higher positions despite the absence of competition, suggesting they are not tolerant of drier, higher environments.

Conclusions on Competition

  • Competitive Interaction:
    • Brown barnacles are limited by competition from blue barnacles.
    • Blue barnacles are limited by environmental conditions (desiccation at higher levels).
  • Leads to the distinction between fundamental niche and realized niche:
    • Fundamental niche: The full potential range without competitors.
    • Realized niche: The actual range occupied in the presence of competition.
  • Competitive Exclusion: One species may be completely excluded from a part of its niche due to competition.

Intraspecific vs. Interspecific Competition

  • Intraspecific competition: Competition among individuals of the same species.
  • Interspecific competition: Competition between individuals of different species.
  • Intraspecific competition often leads to greater exclusion from niche parts compared to interspecific competition.

Field Experiments on Desert Rodents and Ants

  • Researchers set up exclosures to prevent rodents and ants from entering certain plots, comparing them to control plots.
  • Findings:
    • Seed density increased when both rodents and ants were excluded, indicating both are seed predators.
    • Removing only one species (ants or rodents) still showed increased populations of the other, suggesting competition for seeds.

Mechanisms of Resource Competition

  • Exploitation Competition: Using up a resource faster than competitors.
    • Example: Tree roots absorbing soil nutrients.
  • Interference Competition: Actions of one species inhibit another's access to a resource.
    • Example: Toxic chemical release from walnut trees affecting other plant species.

Coexistence and Competitive Dynamics

  • Two species can coexist despite competition if:
    • The niche dimensions they exploit differ enough (niche differentiation).
    • Intraspecific competition suppresses their own population growth more than interspecific competition.
    • A rarity advantage occurs, where less abundant species experience less intraspecific competition, allowing coexistence.

Character Displacement and Evolutionary Change

  • Character displacement leads to evolutionary changes to reduce competition:
    • Example: Alteration of beak size in finches on islands to utilize different seed sizes.
    • Evidence of character displacement is observed when examining traits in allopatric (separate ranges) versus sympatric (overlapping ranges) species.

Summary of Competition Effects

  • Competition impacts species abundance and distribution, influencing growth, survival, and reproduction.
  • Experimental approaches are vital to test for the existence and impact of competition.
  • Coexistence and evolutionary changes are influenced by competitive dynamics over time.

Introduction to Predation

  • Importance of Predation: Critical in regulating prey populations and shaping community structure.
    • Example: Absence of predators can lead to reliance on specific prey population control.

Adaptations and Dynamics in Predation

  • Both predators and prey evolve strategies for survival:
    • Predators adapt to effectively capture prey (e.g., speed, hunting strategies).
    • Prey develop features to avoid predation (e.g., speed, mimicry, protective coloration).
  • Types of predator adaptations:
    • Speed (e.g., cheetah chasing prey).
    • Camouflage (e.g., flatfish lying on the ocean floor).
    • Mimicry (e.g., caterpillars resembling snakes to deter predators).

Behavioral Adaptations of Prey

  • Schooling: Reduces individual risk by diluting predation chances and enhancing vigilance.
  • Cryptic coloration: Helps prey avoid detection by resembling their environment (e.g., stick insects, leaf-mimicking insects).

Summary of Predation Concepts

  • Understanding predation is crucial for ecology, influencing population dynamics and community composition.
  • Evolution shapes interactions between species, where selection pressures drive the adaptations observed in predator-prey relationships.

Conclusion: The study of niches, competition, and predation emphasizes the complex interactions that shape ecological dynamics and evolutionary processes among species, demonstrating the importance of these relationships in understanding biodiversity and ecosystem functionality.