Host selection by an insect herbivore with spatially variable density dependence

Area of Science:

• Ecology
• Behavioral Ecology
• Evolutionary Biology

Background:

• Phytophagous insects often don't prefer plants that maximize offspring performance.
• Negative density dependence in offspring performance may drive egg dispersal to reduce competition.
• Variability in density dependence among host plants suggests females should assess plant traits predicting density effects.

Purpose of the Study:

• To investigate oviposition behavior in an insect herbivore with density-dependent larval performance.
• To determine if females select plants based on competitor density or the strength of density dependence.
• To understand how females balance competition and host plant quality for offspring survival.

Main Methods:

• Field and greenhouse experiments were conducted.
• Oviposition preferences of insect herbivores were observed.
• Offspring performance under varying densities and host plant types was measured.

Main Results:

• Females exhibited strong preferences for host plants that mediated weak offspring density dependence.
• Females did not avoid plants with high densities of competitors.
• Offspring performance declined steeply with density on most plants in natural populations.

Conclusions:

• Females minimize density dependence effects by selecting plants with weak density mediation, not by avoiding high competitor densities.
• Explaining preference-performance correlations requires considering variation in the strength of density dependence among plant individuals.
• Resource selection behavior is influenced by the variability of density-dependent offspring performance across sites within populations.