Response of Cladophora to different P and N regimes under otherwise non-limiting conditions in cultures of artifical seawater suggests that growth rates would be limited in the field by P and N concentrations in the water column above the algae, but not in the algal bed. Treatment with P over the range 0 to 0.25 mg 2' 1 (with 5.0 mg JT 1 N) and N over the range 0 to 5.0 mg A" 1 (with 0.5 mg fi~l P) produced yields proportional to increasing concentrations.Growth rates were obviously saturated above 0.4 mg 8' 1 N and 0.2 mg JT 1 P, and the response was most dramatic in substrate concentration ranges of 0 to 0.1 mg A" 1 N and 0 to 0.03 mg fi' 1 P.Uptake rates of phosphorus increased in proportion to substrate P concentrations, with the highest rates occurring immediately after conditioning in P-free medium. Rates over a combined light and dark period were typically lower than those measured in the light, which gave a v max of 0.11 mg g" 1 dry weight hr" 1 . Ammonia and nitrate were taken up simultaneously at all concentrations, in the presence of 0.5 mg JT 1 P. There was a clear preference for ammonia, with suppression of nitrate uptake at the highest N substrate concentration. Uptake rates of both N species was highest in the light, with a v^ 1.82 for NH 4 and 0.59 mg g" 1 dry weight hr" 1 for NO 3 .
Many exciting studies have begun to elucidate the genetics of the morphological and physiological diversity of ants, but as yet few studies have investigated the genetics of ant behavior directly. Ant genomes are marked by extreme rates of gene turnover, especially in gene families related to olfactory communication, such as the synthesis of cuticular hydrocarbons and the perception of environmental semiochemicals. Transcriptomic and epigenetic differences are apparent between reproductive and sterile females, males and females, and workers that differ in body size. Quantitative genetic approaches suggest heritability of task performance, and population genetic studies indicate a genetic association with reproductive status in some species. Gene expression is associated with behavior including foraging, response to queens attempting to join a colony, circadian patterns of task performance, and age-related changes of task. Ant behavioral genetics needs further investigation of the feedback between individual-level physiological changes and socially mediated responses to environmental conditions.
Understanding the ecological relevance of variation within and between colonies has been an important and recurring theme in social insect research. Recent research addresses the genomic and physiological factors and fitness effects associated with behavioral variation, within and among colonies, in regulation of activity, cognitive abilities, and aggression. Behavioral variation among colonies has consequences for survival and reproductive success that are the basis for evolutionary change.
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