C.V. Johns

Effects of elevated CO2 and temperature on development and consumption rates of Octotoma championi and O. scabripennis feeding on Lantana camara

We carried out a factorial experiment to explore the effect of doubled CO2 concentration and a 3 °C temperature increase on the development of a complete generation of the beetles Octotoma championi Baly and O. scabripennis Guérin‐Méneville (Coleoptera: Chrysomelidae). These species are biological control agents of Lantana camara L. (Verbenaceae), with a leaf‐mining larval phase and free‐living, leaf‐chewing adults.

Feeding preferences of the Christmas beetle Anoplognathus chloropyrus (Coleoptera: Scarabaeidae) and four paropsine species (Coleoptera: Chrysomelidae) on selected Eucalyptus grandis clonal foliage

Summary Christmas beetles (Coleoptera: Scarabaeidae) (Anoplognathus spp.) and paropsine leaf beetles (Coleoptera: Chrysomelidae) are common defoliators of eucalypts, including several important plantation species, throughout south-eastern Australia. It has already been demonstrated that populations and individuals of several eucalypt species vary in susceptibility to defoliation by these leaf-chewing beetles. The objective of this study was to determine whether significant variation in resistance to insect herbivory was present in Eucalyptus grandis genotypes selected from the hardwood plantation program of State Forests of NSW. Grafted clones from three young trees with significantly less crown damage than neighbouring trees in a plantation established near Byron Bay, NSW, were tested for attractiveness to Anoplognathus chloropyrus adults in a binary choice experiment in the laboratory. Shoots from the resistant grafted ramets were paired with shoots from susceptible seedlings of similar age, and caged with feeding A. chloropyrus adults for 24 h. The Christmas beetles consumed significantly (P ≤ 0.05) less leaf area from the resistant shoots, compared to that consumed from the shoots from susceptible seedlings, when given access to both. The binary choice test method was also used to test feeding preferences of four paropsine chrysomelid species: Paropsis atomaria (adults and larvae), P. variolosa (larvae only), Paropsisterna beata (adults), and a Chrysophtharta sp. (adults), using the same E. grandis genotypes. No significant differences (P > 0.05) in feeding preferences were detected for P. variolosa larvae, P. atomaria adults, P. beata adults or the Chrysophtharta sp. adults. In contrast, P. atomaria larvae displayed a significant preference for foliage from the susceptible seedlings. In a larval development study using P. atomaria larvae, those reared on the susceptible foliage developed approximately five days faster and had significantly higher survival than those reared on resistant foliage. Several leaf traits were also compared between the two types of foliage. Leaves of similar age from the resistant clones did not differ significantly from the susceptible seedlings in terms of carbon to nitrogen content or concentrations of the monoterpene, 1,8-cineole. They did, however, have significantly higher specific leaf weight (SLW). SLW may have the potential for use in rapid screening of E. grandis genotypes for susceptibilty to defoliation by leaf-chewing beetles that prefer young soft foliage.

Ecotones as indicators: boundary properties in wetland-woodland transition zones

Ecotones, representing the transition zones between species or communities, have been suggested as focal points for detecting early shifts in vegetation composition due to anthropogenic impact. Here we examined if changes in ecotone location or properties can be used as reliable indicators of hydrological change in temperate wetland communities. We examined 38 woodland-wetland-woodland transitions, distributed across four sites with different anthropogenic disturbance histories and hydrological traits. We tested whether: 1) the ecotones are associated with environmental gradients, and 2) the location or properties of these ecotones change with disturbance history. Well-defined ecotones were associated with steep gradients in soil depth and soil moisture. Most ecotones showed a change in vegetation from hydrophytic to dryland species. There was also some evidence that in highly disturbed sites the link between ecotones and environmental gradients was less apparent. By sampling across boundaries we can better understand the factors controlling the distribution of species. This allows us to make better predictions about the impacts of anthropogenic change in wetland communities. By investigating the transitions between different vegetation communities we were able to highlight key indicators that could be used to monitor these ecologically sensitive and diverse wetland communities.