Attraction of Melitaea cinxia Butterflies to Previously-Attacked Hosts: A Likely Complement to Known Allee Effects?

Abstract

Clumped distributions of herbivorous insect eggs often result from independent assessments of individual plants by different ovipositing females. Here we ask whether, in addition, plants might be rendered more or less attractive to ovipositing Melitaea cinxia butterflies by presence of conspecific eggs and/or by prior larval attack. Both eggs and larval damage rendered Veronica spicata plants significantly more acceptable; the effect of eggs was particularly strong. Larval damage caused a marginally significant increase in acceptability of Plantago lanceolata, but there was no trend for an effect of eggs on this host. Variable oviposition preferences of Melitaeine butterflies are known to drive their metapopulation dynamics by affecting rates of emigration and patch colonization. Therefore variable host acceptability, as documented here, should do likewise, reducing emigration rates at high population densities where V. spicata is present in the landscape and complementing Allee effects that are already known in this system.

Preference Provides a Plethora of Problems (Don't Panic)

“…This design is satisfyingly simple, though analysis of its results can be complex. Butterflies may respond to previously laid eggs (27,52), and eggs themselves may induce responses in the hosts that alter plant acceptability and influence subsequent choices by the insects. Therefore, unless there is evidence that eggs laid at different times are independent events (e.g., 54), analyses should not assume independence.…”