The effects of temperature on the life history traits of Rhopalosiphum maidis (Fitch) were determined at 6, 10, 15, 20, 25, 30, and 35Ϯ1°C on corn leaves, Zea mays (L.). At 35°C, only a few nymphs survived and completed development, but all failed to reproduce. Total immature stages from birth to adult decreased as temperature increased from 51.7 d at 6°C to 5.2 d at 30°C, but became 8.0 d at 35°C. Overall immature development required 119.05 degree-days above 4.44°C. Adult longevity was as high as 26.7 d at 15°C, but significantly declined at 30 and 35°C. The average adult fecundity was as high as 45 offspring at 15 and 20°C, but dropped to 1.8 at 6°C and 8.6 at 30°C. In general, as temperatures increased, age-specific survivorship (l x ) declined more quickly, but age-specific fecundity (m x ) peaked earlier. At 25°C, the age-specific net maternity (v x ϭl x m x ) was the highest in the early reproductive period, resulting in the highest intrinsic rates of increase (r m ϭ0.329). At 20-30°C, the values of r m were significantly higher than those at lower temperatures. The results indicate that corn leaf aphids probably are better adapted in population growth to a wider range of high temperatures in warm regions.

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The endosymbiotic bacterium Buchnera provides its aphid host with essential amino acids. Buchnera is typical of intracellular symbiotic and parasitic microorganisms in having a small effective population size, which is believed to accelerate genetic drift and reduce the stability of gene products. It is hypothesized that Buchnera mitigates protein instability with an increased production of the chaperonins GroESL. In this paper, we report the expression and functional analysis of trpE, a plasmid-borne fast-evolving gene encoding the tryptophan biosynthesis enzyme anthranilate synthase. We overcame the problem of low enzyme stability by using an anthranilate synthase-deficient mutant of E. coli as the expression host and the method of genetic complementation for detection of the enzyme activity. We showed that the Buchnera anthranilate synthase was only weakly active at the temperature of 26 degrees C but became inactive at the higher temperatures of 32 degrees C and 37 degrees C and that the coexpression with chaperonin genes groESL of E. coli enhanced the function of the Buchnera enzyme. These findings are consistent with the proposed role of groESL in the Buchnera-aphid symbiosis.

The effects of grazing and climate change on primary production have been studied widely, but seldom with mechanistic models. We used a Bayesian model to examine the effects of extreme weather and the invertebrate grazer community on epilithic algal biomass dynamics over 10 years (from January 2004 to August 2013). Algal biomass and the invertebrate grazer community were monitored in the upstream drainage of the Dajia River in Taiwan, where extreme floods have been becoming more frequent. The biomass of epilithic algae changed, both seasonally and annually, and extreme flooding changed the growth and resistance to flow detachment of the algae. Invertebrate grazing pressure changes with the structure of the invertebrate grazer community, which, in turn, is affected by the flow regime. Invertebrate grazer community structure and extreme flooding both affected the dynamics of epilithic algae, but in different ways. Awareness of the interactions between algal communities and grazers/abiotic factors can help with the design of future studies and could facilitate the development of management programs for stream ecosystems.