Pea aphid (Acyrthosiphon pisum) clones have been shown to be adapted to particular host plant species but it is unknown whether there are host races. A 1101 base pair region of the mitochondrial cytochrome oxidase I gene (COI) was sequenced for 21 pea aphid clones that had been collected from different host plants in Canada and the U.S.A. Only five closely related mitochondrial haplotypes were ...

Survival of the glassy-winged sharpshooter, Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), was studied under various constant temperatures and feeding conditions. When provided a host plant (Citrus limon L. Burm. f.) to feed on during a 21-d trial, 100% mortality occurred at 0.1, 3.2, and 40.1 degrees C, whereas an average of 74-76% of adults survived in the 13.2-24.5 degrees C ran...

We investigated one causal explanation for geographic variation in clutch size and aggregative feeding of the pipevine swallowtail, Battus philenor. Populations in California lay larger clutches than those in Texas, and larger feeding aggregations grow at an accelerated rate on the California host plant. Using reciprocal transplant experiments with larvae from California and Texas populations, ...

Phytopathogenic bacteria generally have limited host ranges, often confined to members of a single plant species or genus. This appears to result from negative factors restricting the host range ra.ther than from positive factors which allow the pathogen to infect its hosts. These negative factors are avirulence genes present in the pathogen, which interact with matching resistance genes in the...

The Janzen-Connell hypothesis proposes that plant interactions with host-specific antagonists can impair the fitness of locally abundant species and thereby facilitate coexistence. However, insects and pathogens that associate with multiple hosts may mediate exclusion rather than coexistence. We employ a simulation model to examine the effect of enemy host breadth on plant species richness and ...

Studies of host specificity in tropical insect herbivores are evolving from a focus on insect distribution data obtained by canopy fogging and other mass collecting methods, to a focus on obtaining data on insect rearing and experimentally verified feeding patterns. We review this transition and identify persisting methodological problems. Replicated quantitative surveys of plant-herbivore food...

Extrinsic, host-associated environmental factors may influence postmating isolation between herbivorous insect populations and represent a fundamentally ecological cause of speciation. We investigated this issue in experiments on hybrids between the host races of Eurosta solidaginis, a fly that induces galls on the goldenrods Solidago altissima and S. gigantea. To do so, we measured the perform...

Although host-plant selection is a central topic in ecology, its general underpinnings are poorly understood. Here, we performed a case study focusing on the publicly available data on Japanese butterflies. A combined statistical analysis of plant-herbivore relationships and taxonomy revealed that some butterfly subfamilies in different families feed on the same plant families, and the occurren...

Studying the biochemical responses of different plant species to insect herbivory may help improve our understanding of the evolution of defensive metabolites found in host plants and their role in plant-herbivore interactions. Untargeted metabolic fingerprints measured as individual mass features were used to compare metabolite reactions in three Brassicales host-plant species (Cleome spinosa,...