Academic journal article The American Midland Naturalist

Effect of Host-Plant Genotype and Neighboring Plants on Strawberry Aphid Movement in the Greenhouse and Field

Academic journal article The American Midland Naturalist

Effect of Host-Plant Genotype and Neighboring Plants on Strawberry Aphid Movement in the Greenhouse and Field

Article excerpt

ABSTRACT.-Herbivore movement behavior is a key mediator of how host-plant populations affect herbivore populations. We examined the effects of host-plant genotype and variance among host-plant genotypes on movement rates of apterous strawberry aphids, Chaetosiphon fragaefolii (Cockerell) (Homoptera: Aphididae), on Fragaria chiloensis (L.) P. Mill. In the field we estimated aphid movement rates over several years on experimental populations of five different plant genotypes. In the greenhouse, we followed the movement of individual aphids in plant arrays of a single genotype or three different genotypes. In both cases, aphid apterae movement differed among host plant genotypes, with more movement on higher quality genotypes. Movement rate in the field was also influenced by aphid population size. In the greenhouse, aphids showed no taxis toward particular plant genotypes but left different plant genotypes at different rates. Aphids also tended to move more often among plants in three genotype arrays (with a variety of plant genotypes) than predicted by their movement in single genotype arrays. Our results suggest that dispersal among plants by strawberry aphid apterae is affected by plant characteristics associated with genotype and quality of the host plant for the herbivore.

Introduction

Populations of insect herbivores often inhabit populations of host plants that are heterogeneous in quality as food (Denno and McClure, 1983). In natural systems, plant species or individuals may differ genetically in quality (Fritz and Simms, 1992), and in both natural systems and agricultural monocultures, plants may differ phenotypically in quality as a result of microhabitat, developmental stage or inducible resistance (see, e.g., Lewis, 1984; Rossi and Strong, 1991; Karban and Baldwin, 1997). When hosts vary in quality, herbivore movement becomes an important aspect of the interaction between plant and herbivore populations. The amount and selectivity of herbivore movement will determine how herbivores sample plants and, therefore, how the plants affect herbivore population growth (Underwood, 2004). When herbivores move, they may also suffer performance costs due to energy expended, lost feeding time (Schultz, 1983) , variation in their diet (Stockhoff, 1993) or increased vulnerability to predators (Bergelson and Lawton, 1988). Understanding how herbivores move in heterogeneous environments is thus crucial to understanding how host plants affect herbivore populations and vice versa. As part of a larger study of how genetic variation in host quality influences the population dynamics of a specialist aphid [Chaetosiphon fragaefolii (Cockerell), strawberry aphid], we examined the effect of host [wild strawberry, Fragaria chiloensis (L.) P. Mill.] genotype on among plant movement of aphids in field and greenhouse experiments. In this study, all aphids were apterous, so all movement occurred by walking (or possibly wind transport) rather than flying.

Herbivores may change their movement rates in response to two levels of host-plant variation. First, they can respond behaviorally to the characteristics of individual plants, either through taxis toward preferred or (more commonly) movement away from lesspreferred plants (Bernays and Chapman, 1994). Although studies have documented behavioral responses of many herbivorous insects to individual plant characteristics (Barker et al, 1995; Hannunen and Ekbom, 2002), apterous aphids have sometimes been assumed not to be important dispersers (Jepson, 1983; Honek et al, 1998), and relatively few studies have examined their movement responses to plant characteristics. Apterous aphids are, however, known to move among plants (see, e.g., Tamaki et al, 1970; Edson, 1985; Antolin and Addicott, 1991) and to respond to differences in quality both within plants (Jepson, 1983; Harrington and Taylor, 1990) and among plants (Schotzko and Smith, 1991; Honek et al, 1998). In addition, herbivore movement rate can be affected by the amount of variation among neighboring host plants (Bernays, 1999). …

Search by... Author
Show... All Results Primary Sources Peer-reviewed

Oops!

An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.