Effect of host diet and preflight experience on the flight responses of Microplitis croceipes (Cresson)

Abstract. Female Microplitis croceipes without previous exposure to host diet, feeding damage or faeces, and with no oviposition experience (i.e. inexperienced) exhibited flight tunnel responses towards extracts of faeces from several diet–host species combinations, excluding artificial diet. Inexperienced females exhibited the following preference order towards faeces from Heliothis zea larvae fed selected diets: cotton > wild geranium > cowpea > artificial diet, suggesting and adaptation to 'preferred' host plants.
Females having a preflight experience with a plant-host complex (PHC) prior to testing exhibited a higher percentage of oriented flights in the wind tunnel than did inexperienced females. Oviposition Per se had little effect on the flight response of females. The increased flight response after an experience is apparently due to a combination of sensitization and associative learning. In a choice situation, a single experience was insufficient to establish a preference for the PHC experienced; however, repeated experience resulted in preferences, and the degree of preference tended to increase with the number of experiences.     

Morphometric discrimination among females of sibling species of Aconophorini (Homoptera: Membracidae)

Abstract. Keys to species of auchenorrhynchous Homoptera are often based on male features, leaving no means for identifying females other than association with males. As a possible solution to this problem, we examined the use of linear discriminant functions derived from morphometric data (ten linear measurements among homologous body landmarks) for distinguishing females in two groups of sibling species in the Neotropical treehopper tribe Aconophorini (Membracidae: Membracinae): (1) Calloconophora caliginosa (Walker) and C.pinguis (Fowler); and (2) Guayaquila minuta (Fowler), G.venezuelensis Dietrich, and Central and South American populations of G.pallescens (Stål). Samples of female specimens identified by association with males were used to derive the discriminant functions. Performance of these discriminant functions as evaluated by jackknifing the data was as follows: 98.11% of the specimens in the first group correctly identified using a combination of three measurements, and 94.94% of the specimens in the second group correctly identified using a combination of ten measurements.     

Effects of temperature and elevated CO2 on cell division in shoot meristems: differential responses of two natural populations of Dactylis glomerata L.

The aim was to establish whether temperature and/or elevated [CO₂] (-700 μmol mol^?1) affects the cell doubling time (cdt) in the different zones of the shoot apex of two natural populations of Dactylis glomerata originating in Portugal (38° S3′ N) and in Sweden (63° 09′ N). In the Portuguese population at ambient [CO₂], only the pith rib meristem (PRM) exhibited a significant shortening of cdts from 10 to 30 °C. Elevated [CO₂] resulted in a significant shortening of cdt, particularly in the PRM where cdt was reduced 4-8- and 6-1-fold at 10 and 20 °C, respectively, but only 2-fold at 30 °C. In the Swedish population at ambient [CO₂], there were no consistent temperature-dependent alterations to cdt and this population was less responsive to elevated [CO₂] than the Portuguese population. Nevertheless, elevated [CO₂] resulted in a significant shortening of the cdt for some of the zones; the maximum reduction occurred in the PRM at 30 °C. We concluded that in the shoot apex of the Portuguese population, and most notably in the PRM, 10 and 20 °C were non-optimal temperatures for cell division, whilst the Swedish population was relatively buffered against temperature change. Elevated [CO₂] resulted in substantially greater reductions in cdts in the shoot meristem of the Portuguese population than in that of the Swedish population.     

Models to examine containment and spread of genetically engineered microbes

Genetically engineered microbes (GEMs) have the potential to revolutionize agricultural techniques by facilitating crop protection and increased productivity. However, there has been widespread concern regarding the potential impact these microbes may have on the environment. Here we mathematically model the dynamics of GEMs in an agricultural setting, focusing on parameters that can be used to summarize the potential of modified microbes for persistence and spread. First developing a comprehensive model for the dynamics of GEMs which includes mobile and stationary classes of GEMs as well as competition from indigenous microflora, we then analyse a sequence of simplified mathematical models with a view to answering two fundamental questions: (1) will the GEMs spread (or invade), and if so how quickly? and (2) what are the best strategies for containing the spread of GEMs in a spatially varying environment?