Fine-tuning egg stacking: plasticity in a protective parental behavior

FINE-TUNED EGG STACKING: PLASTICITY IN A PROTECTIVE PARENTAL BEHAVIOR

 

JOSEPH B. DEAS – Graduate Interdisciplinary Program in Entomology and Insect Science, University of Arizona

P.O. Box 210007

Tucson, Arizona 85721

 (619) 244-8914

jbdeas@email.arizona.edu

 

MARTHA S. HUNTER – Department of Entomology, University of Arizona

Department of Entomology at the University of Arizona

Forbes 410, PO Box 2100: (36)

Tucson, AZ 85721-0036

(520) 621-9350

mhunter@ag.arizona.edu

 

Mothers may alter the quality of their offspring when experiencing environmental variation. As a consequence of limited resources, increasing offspring quality and making them more fit to deal with harsher environments may limit offspring quantity. If increasing offspring quality is very costly, we would expect organisms to evolve a phenotype that matches the level risk. The seed beetle Mimosestes amicus covers viable eggs with small inviable egg(s) that protect the bottom egg from parasitism by Uscana semifumipennis. Stacking eggs in this way increases the quality of bottom eggs and reduces egg mortality caused by parasitic wasps. However, stacking involves a cost. When wasps are absent, beetles lay more single eggs, and more offspring, highlighting the adaptive value of flexible stacking behavior. We tested whether M. amicus could reverse egg stacking in the absence of parasitism, and how stacking increases with increasing the intensity of wasp cues. The results indicate that egg stacking is very labile and can respond to changes in cue intensity, enabling beetles to fine-tune their response to a changing environment.