Patterns in Population Change and the Organization of the Insect Community Associated with Goldenrod

Abstract

The extent to which insect communities are organized is poorly understood because few studies have examined both population-level processes and community-level patterns. Furthermore, our view of phytophagous insect populations is probably biased by the more frequent attention given to economic pests whose dynamics might be expected to be somewhat exceptional. Herein, we report on the population dynamics and community-level features in a diverse, native fauna of phytophagous insects associated with goldenrod (Solidago altissima), a native perennial plant that forms a dominant, long-persisting element in old-field succession. The data consist of censuses taken in six consecutive years at 16 old fields in the Finger Lakes Region of New York; five additional stands were followed for four consecutive years. Our analyses address two questions: (a) to what extent is the functional structure of the community (as reflected in such attributes to the herbivore load, guild spectrum, and dominance hierarchy) maintained by compensatory changes in the densities of the member species and (b) are certain traits associated with a species' tendency to fluctuate in density or to dominate the community?In general, populations of goldenrod insects fluctuated less than those of insects reported in the literature. Few were abundant; only 7 of the 138 species in the goldenrod fauna ever reached densities at which their biomass exceeded 0.1% of the leaf biomass. The functional structure of the community, as reflected in the total herbivore load and the proportions of that load contributed by various guilds, varied widely in space and time. A small subset of the fauna remained dominant throughout the study; these species, whose populations occasionally irrupted, retained their high rank in relative abundance even during those periods when their populations were waning. There was no evidence for compensatory changes in the densities of species within guilds, as would be expected if a relatively distinct set of limiting resources were available to insects with different feeding styles. Species were no more likely to exhibit negative correlations with their guild mates than they were with members of other guilds. There was also little evidence of sporadic or diffuse competition within the fauna as a whole; even during population outbreaks, the dominant species rarely engendered decreases in the biomass or diversity of the remaining species, and increases in the total herbivore load were seldom associated with losses of species from the community. Several species were positively associated with one another on the basis of similar habitat requirements or the use by one species of conditions created by the presence of another.The community was predictable only in the sense that dominant species remained dominant and rare species rare. The abundance and population variability of species were not correlated with such traits as body size, generation time, or host range. Taxon-related trends, on the other hand, stood out; coleopterans tended to be a...

Insect‐plant interactions on a planet of weeds

“…In later succession, Carson & Root (2000) found that the outbreak of the leaf beetle M. vittata specializing on goldenrod S. altissima destroyed an old-field canopy dominated by goldenrods, thereby increasing the abundance of woody species and speeding plant succession from the herb-dominated to the treedominated stage. In a survey of 16 sites over six years, the same few species were dominant across all sites; notably the leaf chewer T. virgata, the leaf miner M. vittata, and the sap-feeder P. spumarius (Root & Cappuccino, 1992).…”

Influence of polyploidy on insect herbivores of native and invasive genotypes ofSolidago gigantea(Asteraceae)

“…T. virgata is an outbreak insect that can be a major defoliator of S. gigantea and related species in North America. 21 We grew plants originating from 10 populations in the US and 20 populations in Europe in common gardens at the University of WisconsinMilwaukee Field Station in Saukville, Wisconsin. There were five plant origincytotype combinations: three cytotypes from the US and two from Europe.…”

Limenitis arthemis astyanax(Fabricius) (Nymphalidae) Sipping Cercopid-Spittle on Tall Goldenrod,Solidago altissimaL. (Asteraceae)

“…In the Finger Lakes Region of New York alone, Root & Cappuccino (1992) documented 138 species of insects that feed on leaves, stems, or sap of tall goldenrod, Solidago altissima L. With its prodigious flowering display in late summer and early autumn, S. altissima is also visited by numerous species of pollen-, nectar-, flower-, and seed-feeding insects (Gross and Werner 1983;Sholes 1984). Therefore, I was not surprised during my studies of goldenrod in Virginia to see adults of the red-spotted purple, Limenitis arthemis astyanax, making repeated visits to S. altissima in early September-until I realized that the plants had yet to open any flowers.…”