Structure of the Encounter between Goldenrod (Solidago Altissima) and Its Diverse Insect Fauna

Abstract

Most plant species are attacked by insects with widely different feeding styles and life histories. As a first step toward understanding how plants adapt to such diverse pressures, we investigated the population responses of 17 insect species to the genotypic variation exhibited by clones of goldenrods, Solidago altissima, that were drawn from the same population and grown in common gardens. A cluster analysis on the genetic correlations between the insects' responses produced four groups, termed "herbivore suites," that are attracted and repelled by similar plant genotypes (and their underlying sets of traits). There was no obvious correspondence of an insect's phylogenetic affinity, host range, or feeding style with its membership in a particular suite. Put another way, insects belonging to the same family or guild respond differently to genetically variable traits in populations of this native, perennial plant. We found no negative genetic correlations among suites and few among pairs of species, which suggests that trade—offs between the plant's resistance traits are relatively unimportant. The existence of suites of herbivores, whose members exhibit correlated patterns of abundance on different host genotypes, has several interesting consequences. First, the genetic variability of the plant population will be reflected in the diversity and composition of the insect community. Second, selection caused by one herbivore species can result in increased resistances to other, rarer species whose responses are correlated with those of the damaging species. Third, selection by suites of herbivores may be more intense and less variable than selection by individual insect species, especially when many species are rare. By recognizing that resistance can evolve as a function of selection by entire suites of species we can develop better estimates of selection and perhaps achieve a greater understanding of the process of diffuse coevolution. The linkage of interactions within suites suggests some unexplored possibilities for explaining the rarity of many insect species.

PATTERNS OF SELECTION ON PHYTOPHAGE RESISTANCE IN IPOMOEA PURPUREA

“…One reason for this may be that it has seldom been recognized that there are many possible causes of nonindependent evolution of resistances. These include, but are not limited to (1) the existence of genetic correlations among traits conferring resistance to different parasites (e.g., Kinsman 1982;Rausher and Simms 1989;Maddox and Root 1990), which may under some circumstances constrain the evolution of resistance even if there is directional selection acting directly on each resistance trait (Rausher 1992); (2) effects of one parasite on the abundance of, or susceptibility ofa hostto, another (e.g., Carroll and Hoffman 1980;Kuc 1982Kuc , 1987Fritz et al 1986;Karban 1986;Karban et al 1987;Apriyanto and Potter 1990;Fritz 1992;Rausher et al 1993); and (3) nonadditivity of the impact of two parasites on host fitness (e.g., Dickinson 1979;Powell 1979;Strauss 1991). [A general model indicating how (2) and (3) lead to nonindependent evolution of resistances is provided by Hougen-Eitzman 1991.…”

Macroevolution and the biological diversity of plants and herbivores

“…Even crude measures of the toxicity or deterrent effects of specific compounds across a wide array of insects appear to be rather rare, and those few suggest that effects are not highly correlated across herbivores (53)(54)(55). Genetic correlations of resistance of whole plants against various herbivores are also rather low (56)(57)(58), but these correlations, across genotypes that vary in many characters, may say little about the cross-effectiveness of any one defense character.…”

Prior flea beetle herbivory affects oviposition preference and larval performance of a potato beetle on their shared host plant

“…Because a single plant species generally hosts numerous species of herbivores, an insect ovipositing in a host population will commonly encounter plants that display a range of prior herbivory (Maddox & Root, 1990;Fritz, 1992). While studies of the effects of prior herbivory on larval performance often show that insect growth or survival is worse on damaged plants than on undamaged controls (e.g.…”