PERFORMANCE OF TRIRHABDA VIRGATA (COLEOPTERA: CHRYSOMELIDAE) ON THREE POTENTIAL HOSTS

Abstract

The Canadian Entomolopist 131: 801 -811 (1999) The suitability ofthree potential host plants, Solidago canadensisL. var. canadensis (Asteraceae), Solidago graminifulia (L.) Salisb., and Aster lateriflorus L. (Asteraceae), for the goldenrod beetle, Trirhabda virgata LeConte was determined by measuring several fitness components during the T. virgata life cycle. Neonate larvae were collected from S. canadensis plants and transplanted onto S. canadensis, S. graminifulia, and A. lateriflorus and maintained in field enclosures until the last instar was reached. Once brought into the laboratory, larvae were fed their assigned host plant until pupation. Following emergence, adults were weighed and separated into mating pairs to record oviposition and longevity. Eggs were kept in the laboratory until the following spring, when first instar larvae were taken into the field and re-established on their assigned host, and the experiment was repeated for 2 years. Larval survival and rate of development was not affected by the host plant. Mean weight of adults at emergence was greater on S. canadensls than on either S. graminifulia or A. lateriflorus. Two components of adult fitness, postmating longevity and realized fecundity, were measured. Longevity of adult fernale T. virgata was not affected by the host plant. Fecundity of Z virgata reared on A. lateriflorus and S. graminifulia was lower than the fecundity of females reared on S. canadensis. These results are consistent with the hypothesis that both intrinsic plant quality and the mobility of the foraging stage are important in the evolution of host range in T. virgata. These experiments were repeated over a 3-year period, using offspring from the survivors of the previous year for the 2nd and 3rd years. Over this time, individuals experienced "laboratory adaptation," and both accepted and increased their performance on previously unacceptable food plants. Blatt SE, Schindel AM, Harmsen R. 1999. Performance de Trirhabda virgata (Coleoptetu : Chrysomelidae) chez trois h6tes potentiels. The Canadian Entomologist 131 : 801-811. ' Author to whom all conesoondence should be addressed THE CANAJ3IAN ENTOMOLOGIST NovemberDecember 1999pas Ct C affectCe par la nature de l'hbte. En revanche, la fCconditC des insectes s'est avCrCe plus faible chez les femelles ClevCes sur A. lateriflorus et S. graminifolia que chez celles ClevCes sur S. canadensis. Ces rksultats sont en accord avec l'hypothkse selon laquelle la qualit6 intrinskque des plantes hbtes et la mobilitC des stades consommateurs de l'insecte sont des facteurs dttenninants de 1'Cvolution de 1'Cventail d'hbtes chez T. virgata. Ces expkriences ont Ct C rCpCtCes au cours d'une pCriode de 3 ans pendant lesquelles les rejetons des survivants de l'annCe prCcCdente ont Ct C utilisCs au cours de la 2" et de la 3" annCes. Durant ce temps, les insectes ont subi une "adaptation en laboratoire" et ont accept6 de nouvelles plantes hbtes et y ont meme amCliorC leur performance.[Traduit par la RCdaction]

Host-Associated Genetic Differentiation in Phytophagous Insects: General Phenomenon or Isolated Exceptions? Evidence From a Goldenrod-Insect Community

“…Among insects in our survey that do not make galls, only the stem borer Mordellistena exhibits HAD Blair et al 2005). The external leaf-chewing Trirhabda species (which are reported as herbivores of several additional Solidago species as well as species in Aster; Messina and Root 1980;Messina 1982;Blatt et al 1999) do not exhibit evidence of HAD, consistent with their relatively less intimate associations with the host plant. We are currently expanding our genetic surveys to include more species, both gall-making and of other feeding guilds, to achieve statistical power in comparative analyses of the sort outlined here.…”

Disarming the paradox of sublethal plant defense against insects: Trirhabda virgata larval development time and leaf tissue loss on Solidago altissima

“…In addition, the appropriate data consist of comparisons among genetically variable individuals within a natural plant population. Previous studies have compared the development time–tissue consumption (or mass gain) relationship between different plant species (Scriber, 1981; Blatt et al., 1999; Bossart, 2003), between plant individuals differing due to environmental variation (Loader & Damman, 1991; Wise & Weinberg, 2002; Lower et al., 2003), or even between genetically engineered variants (Winterer & Bergelson, 2001). Such studies have their own purposes and merits, but they are not appropriate for addressing the core assumption of the sublethal‐defense paradox in terms of the evolution of genetically controlled traits.…”

Food limitation and insect outbreaks: complex dynamics in plant–herbivore models

“…In particular, there is evidence that Solidago is self‐limited (Hartnett & Bazzaz 1985), that leaf‐chewing by Trirhabda can reduce Solidago population growth (Sholes 1981; McBrien, Harmsen & Crowder 1983; Cain, Carson & Root 1991; Meyer & Root 1993; Long et al . 2003), and that Trirhabda are food‐limited (Brown & Weis 1995; Blatt, Schindel & Harmsen 1999; Appendix S2). Trirhabda are univoltine and the perennial Solidago grows new above‐ground shoots each year, so both the edible plant biomass and the insect population are well described by discrete‐time models.…”