Abstract Detail

Symbioses: Plant, Animal, and Microbe Interactions

Woodard, Anastasia [1], Ervin, Gary [2], Marsico, Travis [3].

Defense Priming as a Mechanism to Combat Newly-Associated Insect Herbivores.

To combat insect herbivory and still achieve optimal allocation of resources, plants have evolved inducible defenses. Defense priming enhances the induced defense responses of plants by activating defense pathways prior to attack due to airborne signals released from neighboring plants undergoing herbivory. This phenomenon allows plants to mount quicker, more intense responses specifically tailored to the threatening herbivore. Despite the number of newly-associated invasive insect species globally, the effects of defense priming in a system with a novel threat have not been considered. Here we report that plants can be induced to defend against an otherwise unrecognized, newly-associated insect herbivore when signaled by plants actively defending against a co-evolved insect herbivore. Opuntia humifusa and O. stricta, two North American pricklypear species, have not been observed to defend against the recently-introduced invasive cactus borer Cactoblastis cactorum in nature, although defenses such as mucilage production and tissue necrosis are commonly observed when plants are fed on by the native North American cactus borer Melitara prodenialis. In a recent laboratory experiment, we found that 47% of plants fed on by C. cactorum grown in the presence of plants fed on by M. prodenialis defended with mucilage and necrosis responses, whereas 17% of plants grown only with C. cactorum showed defenses within the first month of larval feeding. Induced defense via priming of the Opuntia spp. increased the larval period of C. cactorum by 38% (from a mean of 69 days to 95). In nature where larvae are exposed to predators, parasitoids, and pathogens, an increase in larval period is expected to decrease fitness. Our results indicate that defense priming initiated by native, co-evolved herbivores can cue naïve plants to defend against invasive herbivores. These findings have important implications for our understanding of defense priming in the context of species invasions and the influence of evolutionary history on plant-herbivore interactions.

Broader Impacts:

1 - Arkansas State University, Department of Biological Sciences, PO Box 599, State University, AR
2 - Mississippi State University, Department of Biological Sciences, 130 Harned Hall, Lee Blvd, Mississippi State , MS, 39762, USA
3 - Arkansas State University, Department Of Biological Sciences, PO Box 599, State University, AR, 72467, USA

Keywords:
defense priming
Cactoblastis cactorum
Melitara prodenialis
Opuntia humifusa
Opuntia stricta
plant-animal interactions. 
plant signaling.

Presentation Type: Oral Paper:Papers for Topics
Session: 38
Location: Portland Room/Chase Park Plaza
Date: Tuesday, July 12th, 2011
Time: 4:30 PM
Number: 38004
Abstract ID:616