Aphid reproductive investment in response to mortality risks

Area of Science:

• Entomology
• Microbiology
• Evolutionary Biology

Background:

• Aphids rely on microbial endosymbionts for essential nutrients and protection.
• Limited aphid immune function may increase vulnerability to pathogens.
• Aphids might increase reproduction as a non-immunological response to infection or risk.

Purpose of the Study:

• To investigate if pea aphids increase reproduction in response to immunological challenges.
• To determine if aphid alarm pheromone exposure influences reproduction.
• To examine the role of symbiotic bacteria in mediating these reproductive responses.

Main Methods:

• Pea aphids were subjected to immunological challenges (stabbing with sterile or bacteria-laden needles).
• Aphids were exposed to aphid alarm pheromone (E)-β-farnesene (EBF).
• Reproductive output was compared between challenged and control aphids, with and without specific symbiotic bacteria.

Main Results:

• Abdominal stabbing reduced fecundity; heat-killed bacteria exposure had an intermediate effect.
• Symbionts did not generally alter aphid reproduction in response to bacterial exposure.
• Exposure to alarm pheromone increased reproduction in aphids with Hamiltonella defensa or Serratia symbiotica, but not others.

Conclusions:

• Pea aphids can increase reproduction in response to specific risk cues.
• The presence of certain symbiotic bacteria can modulate this reproductive plasticity.
• Increased reproduction under risk benefits both the aphid host and its vertically transmitted symbionts, enhancing overall fitness.