Final Exam

Koinobiont vs. Idiobiont

  • Koinobiont:
      - Definition: A type of parasite that allows the host to continue to grow and develop after parasitism.
      - Implication: The survival and growth of the host may support the long-term survival of the parasite, as it remains dependent on the host's resources.

  • Idiobiont:
      - Definition: A type of parasite that immediately halts the host's development upon attack.
      - Implication: The host's suspension of development makes it an unsuitable environment for many parasites, limiting their opportunities for growth and reproduction.

Centrifugal Phylogenetic Method

  • Definition: A risk-assessment testing sequence used in biological control.

  • Procedure: Start with species that are most closely related to the target pest and then move outward through phylogenetic relationships to define the host range.

Specialist vs. Generalist Trade-off

  • Specialists:
      - Definition: Organisms that have high host specificity.
      - Advantage: Safer due to reduced non-target effects.
      - Disadvantage: Prone to "boom-bust" cycles due to their dependence on a limited number of hosts.

  • Generalists:
      - Definition: Organisms that can utilize a broader range of hosts.
      - Advantage: Provide more stable suppression of pest populations.
      - Disadvantage: Higher risk of non-target effects and potential ecological disruption.

Host-Specific Herbivores

  • Preferred for Weed Biocontrol:
      - Rationale: Must not feed on crops or native plants to avoid ecological harm.
      - Example: Air Potato Leaf Beetle, specifically chosen due to its targeting of the invasive Air Potato plant.

Type II vs. Type III Response

  • Type II Response:
      - Definition: A functional response where the predation rate slows as prey density increases, largely due to handling time of the predator.

  • Type III Response:
      - Definition: A sigmoidal (S-shaped) functional response where low prey density provides a refuge for prey.
      - Mechanism: Often due to predators' learning effects; they become more efficient at capturing abundant prey while being less effective when prey is scarce.

Density Dependence

  • Definition: Central to biocontrol regulation; it states that natural enemies kill a larger proportion of the pest population as pest density increases.

Allee Effects

  • Definition: A phenomenon where small populations may fail to establish because individuals cannot find mates or cooperate effectively.

  • Significance: Critical consideration during the release of biological control agents.

Propagule Pressure

  • Definition: The combined effect of the number of individuals released and the frequency of these releases.

  • Significance: Serves as the best predictor of establishment success for biological control agents.

Intraguild Predation (IGP)

  • Definition: Occurs when two natural enemies consume the same pest while also feeding on each other.

  • Implication: This interaction can lead to increased pest populations if the superior biological control agent is predated upon.

Natural Enemy Release Hypothesis

  • Theory: Invasive species become pests because they escape their coevolved natural enemies in their native range.

  • Relevance: This hypothesis supports the practice of reintroducing natural enemies to restore ecological balance.

Pesticide Treadmill

  • Definition: A cycle in which the use of pesticides results in the elimination of natural enemies, leading to pest resurgence or secondary outbreaks.

  • Consequences: This process necessitates the use of higher doses of pesticides or the introduction of new chemicals to control pest populations.

Classical vs. Augmentative Biological Control

  • Classical Biological Control:
      - Definition: Involves a one-time introduction of a biological control agent for permanent establishment within the ecosystem.

  • Augmentative Biological Control:
      - Definition: Involves periodic releases of biological control agents for temporary or seasonal pest management.

Inundative vs. Inoculative Releases

  • Inundative Releases:
      - Definition: Characterized by a massive release of agents meant for immediate pest suppression, effectively acting as a biological pesticide.
      - Expectation: No expectation for establishment of the agents within the ecosystem.

  • Inoculative Releases:
      - Definition: Involves small initial releases with the expectation that these agents will reproduce and provide pest control throughout the season.

Conservation Biocontrol

  • Definition: An approach that involves modifying the environment (such as creating beetle banks or floral strips) to enhance the effectiveness of already present natural enemies.

Biological Control vs. Natural Control

  • Natural Control: Maintenance of population densities through abiotic and biotic factors without human intervention.

  • Biological Control: A proactive strategy wherein human intervention manipulates living organisms to suppress specific pest populations.

Consequences of Synthetic Pesticide Reliance

  • Three Primary Negative Consequences:
      1. Pesticide Treadmill: Lead to resurgence or resistance in pest populations.
      2. Decline in available pesticides: Due to regulatory constraints and low discovery rates of new compounds.
      3. Unsuitability for long-term management: Ineffective for controlling invasive species sustainably.

Definitions of Biological Control

  • Strict Definition: Only living agents (including viruses) qualify as biological control agents; metabolites or chemical signals, such as pheromones or insect venom-derived insecticides, are categorized as “biorational” or “biologically based” tools.

Enemy Release Hypothesis

  • Concept: Suggests a species can become invasive in a new environment after escaping the “top-down” control pressure of its natural enemies.

  • Implication: Classical biological control seeks to reintroduce these natural enemies to maintain ecological balance.

Inundative vs. Inoculative in Augmentative Biological Control

  • Comparison:
      - Inundative releases aim for immediate reduction in pest populations with no intent for agent establishment.
      - Inoculative releases set the stage for a population increase that can lead to accumulated pest control over a designated period.

Habitat Modifications in Conservation Biological Control

  • Three Examples:
      1. Providing food resources through floral intercropping which attracts beneficial insects.
      2. Offering water through supplemental sources, such as small ponds or reservoirs.
      3. Providing shelter, including beetle banks or overwintering boxes to enhance habitat for natural enemies.

Targeting Arthropods in Weed Biocontrol

  • Reason for Focus: Arthropods exhibit higher host specificity, have co-evolved relationships with host plants, and can inflict consistent damage without the extensive ecological risks that can stem from vertebrate predation.

Cumulative Stress Hypothesis vs. Lottery Model

  • Cumulative Stress Hypothesis: Proposes that control success results from the combined effects of multiple agent species working together.

  • Lottery Model: Suggests that with the introduction of additional species, the probability of encountering the one highly effective agent capable of significantly impacting pest dynamics increases.

Feeding Guild Impact on Plant Fitness

  • Most Impactful Insects: Insects that target roots or stems (such as borers) demonstrate more substantial effects on plant fitness than those that only attack leaves (i.e., defoliators).

Predator vs. Parasitoid Life History

  • Predator:
      - Consumption: Feeds on multiple prey individuals throughout its lifetime.

  • Parasitoid:
      - Lifecycle: Requires only one host to complete its development and results in the host's death.

Types of Biological Control Agents: Koinobionts vs. Idiobionts Revisited

  • Koinobionts:
      - Allows for the host's continued growth and development after parasitization.

  • Idiobionts:
      - Immediately disrupts or halts the biological functioning and development of the host once the attack occurs.

Significance of Type III Functional Response

  • Importance: Creates an S-shaped predation response curve, where low prey densities create a refuge that can prevent complete prey population eradication, ultimately assisting in maintaining long-term population stability.

Centrifugal Phylogenetic Method Explained

  • **Steps:
      1. Test plants or animals closely related to the target pest (typically within the same genus).
      2. Progress outward to more distantly related groups (first to the same tribe, then to wider categories like family) to comprehensively define safe host ranges for biological control agents.

Three Pillars of Environmental Compliance in Biocontrol Agent Release

  • Central Insight of Propagule Pressure:
      - Combines the number of individuals and the frequency of releases.
      - Rationale: Larger or more frequent releases mitigate risks from demographic stochasticity and Allee effects, such as difficulties in mate finding, thereby enhancing the establishment of the biological control agents.