Intraspecific interference among larvae in a semivoltine dragonfly population

Area of Science:

• Ecology
• Behavioral Ecology
• Population Dynamics

Background:

• Intraspecific competition is crucial for population dynamics.
• Size-dependent interactions can significantly impact community structure and function.
• Aquatic arthropod predators exhibit complex competitive behaviors.

Purpose of the Study:

• To investigate how size distribution of dragonflies (Tetragoneuria cynosura) affects competitive interactions.
• To differentiate between feeding interference, interference mortality, and dispersal effects.
• To understand the role of larval size classes in population regulation.

Main Methods:

• Three field experiments and one laboratory experiment were conducted.
• Colonization patterns of different larval size classes were monitored.
• In-situ functional responses and interference mortality were quantified.

Main Results:

• Passive colonization by small larvae was observed initially.
• High densities of large larvae inhibited colonization by small larvae.
• Small larvae exhibited reduced movement (dispersal inhibition) when with larger conspecifics.
• Interference mortality, particularly on larger small larvae, was evident.
• Large larvae showed feeding interference among themselves.

Conclusions:

• Inhibition of small larvae is likely due to interference mortality, not dispersal.
• Colonization and interference interact to determine local larval density.
• Size-dependent interference effects are complex and challenging to detect experimentally.