Does mama know best? Butterfly oviposition choice and caterpillar performance depends on host-plant age

QUINTERO C

Denver, Colorado

Encuentro; 20th High Country Lepidopterists Meeting; 2009

Denver Museum of Nature & Science, Denver, Colorado

Plant ontogeny has been shown to affect the expression of numerous plant traits relevant to herbivores such as nutritional content as well as physical and chemical defenses. However, we know little about how these plant traits changes across multiple developmental stages of a plant species or how herbivore species respond to those changes. In order to evaluate how oviposition preferences and caterpillar performance vary among multiple developmental stage of the same host plant, Buckeye butterflies (Junonia coenia Hubner, Nymphalidae) were exposed to greenhouse Plantago lanceolata L. (Plantaginaceae) plants of five distinct ontogenetic stages. Two choice tests were performed: 6 vs. 8 vs. 10 wks-old plants and 10 vs. 14 vs. 18 wks-old plants. After 72hrs, I recorded the number of eggs on each of the three plants. To evaluate caterpillar performance, one newly-hatched larva was placed on each of 20 plants per ontogenetic stage using four of the stages offered to butterflies: 6, 10, 14 and 18 wks-old plants. Larvae were monitored and weighed every five days from 2nd instar to pupation, and survival rate, growth rate, and developmental time determined. Plant age significantly influenced both butterfly oviposition choice and caterpillar performance. Buckeye butterflies greatly prefer young developmental stages of P. lanceolata. In accordance with the "mother knows best" hypothesis, caterpillars also performed better on young developmental stages of P. lanceolata. Mortality rate reached 80% on reproductive and post reproductive stages while mortality decreased to 55 and 5% in juvenile and seedling stages, respectively. In addition, surviving caterpillars developed significantly faster and reached higher pupa weights on seedlings, decreasing performance as host plants aged. These results demonstrate that changes in plant traits throughout plant development can greatly influence insect herbivores by directly altering herbivore preference and performance.