Phenotypic variation in food utilization in an outbreak insect herbivore

The effects of nutrition may have subtantial impact on insect evolution by shaping different components of phenotypes. The key to undestanding this evolutionary process is to know how nutritional condition affects additive and nonadditive components of the phenotype. However, this is poorly understood in outbreaking insects. We investigated the additive and nonadditive variation present in food utilization traits in spruce budworm individuals subjected to chronic nutritional stress. A total of 160 full-sib families of spruce budworm （Choristoneurafumiferana Clem.） were raised under laboratory condi- tions, feeding on 2 diets （high and low energy） during 3 generations. Variables tested were pupal mass, consumption rate （RCR）, growth rate （RGR）, approximate digestibility （AD）, the efficiency of conversion of digested food （ECD） and the efficiency of conversion of ingested food （ECI）. Our results show that all traits tested presented a high percentage of nonadditive effects that modulate phenotype expression. We found a significant impact of family × diet interaction on pupal mass, RGR and ECD. Furthermore, these traits exhib- ited the greatest heritability. There was no evidence of presence of maternal effects. The results revealed that food utilization traits may evolve through epigenetics effects, such as phenotypic plasticity. This information can be used by modellers to improve forecast of spruce budworm population dynamics.

Feeding performance of Clostera fulgurita on three clones of Populus deltoides

Poplar leaf defoliator, Clostera fulgurita （Walker） larvae were reared on three Populus deltoides clones （PL1, PL5 and PL7） in the laboratory. The nutritional indices were computed for working out the relationship between food consumption and growth rate of 3rd, 4th and 5th instar larvae on three clones. The result showed that the consumption index （CI）, approximate digestibility （AD）, growth rate （GR）, relative growth rate （RGR） and efficiency of conversion of ingested food （ECI） decreased with the increase in the age of the larvae. Efficiency of conversion of digested food （ECD） increased with increase in age of the larvae. GR and RGR varied significantly, indicating that larval development was enhanced on PL1 as compared to PL5 ＆ PL7. The values of AD, ECI and ECD were not affected by the different clones. Feeding and growth indices could be useful to define a defoliation prediction model.

Azotobacter inoculation can enhance the resistance of Bt cotton to cotton bollworm, Helicoverpa armigera

The rising trend in the cultivation of Bacillus thuringiensis (Bt) transgenic crops may cause a destabilization of agroecosystems, thus increasing concerns about the sustainability of Bt crops as a valid pest management method. Azotobacter can be used as a biological regulator to increase environmental suitability and improve the soil nitrogen utilization efficiency of crops, especially Bt cotton. A laboratory test investigated effects on the development and food utilization of Helicoverpa armigera fed with different Cry1Ab/Cry1Ac proteins and nitrogen metabolism-related compounds from cotton (transgenic variety SCRC 37 vs non-Bt cotton cv. Yu 2067) inoculated with Azospirillum brasilense (Ab) and Azotobacter chroococcum (Ac). The findings indicate that inoculation with Azotobacter significantly decreased the partial development and food utilization indexes (pupal weight;pupation rate;adult longevity;fecundity;relative growth rate, RGR;efficiency of conversion of digested food, ECD;and efficiency of conversion of ingested food, ECI) of H. armigera fed on Bt cotton, but contrasting trends were found among these indexes in H. armigera fed on non-Bt cotton inoculated with Azotobacter, as a result of differences in Bt toxin production. Overall, the results showed that inoculation with Azotobacter had negative effects on the development and food utilization of H. armigera fed on Bt cotton, leading to enhanced target insect resistance. Presumably, Azotobacter inoculation can be used to stimulate plant soil nitrogen uptake to increase nitrogen metabolism-related compounds and promote plant growth for Bt and non-Bt cotton, simultaneously raising Bt protein expression and enhancing resistance efficacy against cotton bollworm in Bt cotton.

Assessing the bird guild patterns in heterogeneous land use types around Jammu,Jammu and Kashmir,India

Land-use sprawl in the Himalayas has caused the conversion of natural habitat into human-modified habitats,thus degrading ecosystem health.Adaptation of birds to changing physical environment can be well understood by analyzing their habitat preferences,and foraging dynamics explored to a limited extent in the Himalayan region,as yet.To achieve a comprehensive understanding of avian guild structure,we used multivariate statistical techniques to classify bird species according to their similarities in foraging patterns and habitat preferences.Observations based on habitat and diet affinities accounted for rich avian diversity with a total of 208 bird species(about 15%of country’s avifauna)recorded from six different sites during 1 year survey.Unweighted pair-group average cluster analysis performed on the families revealed ten feeding and fifteen habitat guilds among 63 bird families observed.Subtropical forests harbored more species followed by urban forests and agricultural landscapes.Insectivorous and omnivorous outnumbered other feeding guilds in the study area.Bird assemblages were richer in protected areas and semidisturbed landscapes and did not show significant variation between the seasons.Results of the study revealed that different functional groups of birds behaved differently,primarily induced by choice of food.The site heterogeneity favored avifaunal persistence by providing favorable foraging,roosting,and nesting opportunities to birds.Composition of avian guilds indicated level of intactness and ecological integrity of ecosystems studied.This outcome thus sets the background for long-term analysis of bird-habitat relationship and their foraging dynamics.The study has the relevance for decision-makers to integrate avian guild structure as an essential ingredient in formulating conservation strategies.