For many plant species in eastern North America, short observed seed dispersal distances (ranging up to a few tens of meters) fail to explain rapid rates of invasion and migration. This discrepancy points to a substantial gap in our knowledge of the mechanisms by which seeds are dispersed long distances. We investigated the potential for white-tailed deer (Odocoileus virginianus Zimm.), the dom...

A goal among community ecologists is to predict when and where trophic cascades occur. For example, several studies have shown that forest birds can limit arthropod abundances on trees, but indirect effects of bird predation (i.e. decreased arthropod damage to trees) are not always observed and their context is not well understood. Because productivity is one factor that is expected to influenc...

C:N stoichiometry was investigated in relation to diet (dN), N-deprivation, and worker body size for a diverse assemblage of tropical Amazonian ants. Relative nitrogen (N) deprivation was assayed for 54 species as an exchange ratio (ER), defined as SUCmin/AAmin, or the minimum sucrose concentration, divided by the minimum amino acid concentration, accepted as food by ‡50% of tested workers. On ...

This research tested the long-term effects of defoliation on aspen chemistry and growth in relation to genotype and nutrient availability. We grew saplings of four aspen genotypes in a common garden under two conditions of nutrient availability, and subsequently subjected them to two levels of artificial defoliation. Artificial defoliation suppressed plant growth, and saplings of the four genot...

Environmental variation in food resources modifies performance of herbivores, in addition to genetic variation and maternal effects. In marine benthic habitats, eutrophication may modify herbivores’ diets by changing host species composition or nutritional quality of algae for herbivores. We studied experimentally the effects of diet breadth and nutrient availability for the host algae on fitne...

Plant chemical defenses and escape from natural enemies have been postulated to select for dietary specialization in herbivorous insects. In field and laboratory bioassays, we evaluated the effectiveness of intact and chemically modified larval shield defenses of the generalist Chelymorpha alternans and the specialists Acromis sparsa and Stolas plagiata (Chrysomelidae: Cassidinae) against three...

Mammalian herbivores are predicted to regulate concentrations of ingested plant secondary metabolites (PSMs) in the blood by modifying the size and frequency of feeding bouts. It is theorized that meal size is limited by a maximum tolerable concentration of PSMs in the blood, such that meal size is predicted to decrease as PSM concentration increases. We investigated the relationship between PS...

In order to identify the selection mechanism of two sympatric African browsers, we analysed encounter rates and selection of bushes along foraging pathways. We monitored the tracks, left overnight, by kudu and impala on an experimental plot of natural Acacia nilotica and Dichrostachys cinerea in the highveld of Zimbabwe, and recorded the number of bushes attacked in each category. Both ungulate...

Bark beetles engage in one of the most pronounced examples of group procurement of defended plants. Their aggregation pheromones attract both sexes and are essential to overcome constitutive and rapidly inducible lethal defenses. The relative benefits to senders versus receivers of these signals are only partly understood. Because the initial stage of host entry can be hazardous, there may be b...