Conspecifics, not pollen, reduce omnivore prey consumption

Area of Science:

• Ecology
• Predator-prey dynamics
• Insect behavior

Background:

• Pollen can influence omnivore feeding habits, potentially altering predation on animal prey.
• Omnivore numerical responses to pollen can increase predation, but increased conspecific interactions may suppress it.
• Intraspecific interactions among omnivores are often overlooked in studies of pollen's impact on predation.

Purpose of the Study:

• To investigate how Spartina foliosa pollen and ladybeetle (Naemia seriata) density affect the consumption of scale insect prey.
• To assess the combined effects of pollen availability and conspecific density on ladybeetle predation rates.

Main Methods:

• Three studies were conducted: isolated ladybeetles with pollen, ladybeetles with numerical responses and pollen, and comparing per capita consumption across ladybeetle densities.
• Quantified scale insect consumption by Naemia seriata under varying pollen levels and conspecific densities.
• Statistical analysis to determine the impact of pollen and density on prey consumption.

Main Results:

• Pollen did not affect prey consumption by isolated ladybeetles.
• Pollen increased ladybeetle density but did not alter total prey predation when numerical responses were possible.
• Per capita prey consumption decreased significantly with increased ladybeetle density, with two conspecifics reducing it by 76%.

Conclusions:

• Pollen's effect on population-level predation by omnivores may be minimal when numerical responses are counteracted by reduced per capita consumption due to intraspecific interactions.
• Ladybeetle density is a critical factor mediating the impact of pollen on predation rates.
• Intraspecific interactions can significantly suppress individual predation rates, offsetting potential increases from pollen-driven population growth.