Population cycles caused by selection by density dependent competitive interactions.

Several animal species have cyclic population dynamics with phase-related cycles in life history traits such as body mass, reproductive rate, and pre-reproductive period. Although many mechanisms have been proposed there is no agreement on the cause of these cycles, and no population equation that deduces both the abundance and the life history cycles from basic ecological constraints has been formulated. Here I deduce a population dynamic equation from the selection pressure of density dependent competitive interactions in order to explain the cyclic dynamics in abundance and life history traits. The model can explain cycles by evolutionary changes in the genotype or by plastic responses in the phenotype. It treats the population dynamic growth rate as an initial condition, and its density independent fundament is Fisher's (1930, The Genetical Theory of Natural Selection, Oxford: Clarendon) fundamental theorem of natural selection that predicts a hyper-geometrical increase in abundance. The predicted periods coincide with the cyclic dynamics of Lepidoptera, and the Calder hypothesis, which suggests that the period of population cycles is proportional to the 1/4 power of body mass, follows from first principles of the proposed density dependent ecology.

Interference competition set limits to the fundamental theorem of natural selection.

The relationship between Fisher's fundamental theorem of natural selection and the ecological environment of density regulation is examined. Using a linear model, it is shown that the theorem holds when density regulation is caused by exploitative competition and that the theorem fails with interference competition. In the latter case the theorem holds only at the limit of zero population density and/or at the limit where the competitively superior individuals cannot monopolize the resource. The results are discussed in relation to population dynamics and life history evolution, where evidence suggests that the level of interference competition in natural populations is so high that the fundamental theorem does not apply.

Multi-species risk analysis, species evaluation and biodiversity conservation.

The multi-species conservation approaches starting from Vane-Wright et al. (1991) search for a biologically valid basis to evaluate biodiversity. Such evaluations can be used to optimize reserve boundaries so reserves contain a high level of biodiversity. However, these optimization procedures do not minimize the future loss of biodiversity. We provide a method that can be used to minimize the loss of biodiversity. The method integrates an evolutionary species evaluation with an ecological multi-species risk analysis to estimate the expected loss of phylogenetic diversity. A minimization of this loss will optimize the preservation of phylogenetic diversity.

Recommended dietary allowance for vitamin E: relation to dietary, erythrocyte and adipose tissue linoleate.

The general trend toward increased consumption of polyunsaturated fatty acids is apparent in the linoleate level of adipose tissue (13.0 plus or minus 1.3%) and erythrocyte lipids (14.0 plus or minus 1.9%) in the present group of female undergraduate student volunteers compared to values reported in the early 1960's. On the basis of the level of linoleate in their diets (19.5 plus or minus 0.8%), it is also apparent that further increases in tissue lipid linoleate levels are to be anticipated, which in turn will result in an increased requirement for vitamin E. It is suggested that adipose tissue linoleate levels in the general population be used as a baseline for the periodic evaluation and revision of the recommended dietary allowance for vitamin E. The recommended dietary allowance could then be phrased in terms of the quantity of vitamin E activity to be consumed per gram linoleate in 100 g adipose tissue fatty acids. A recommendation of 0.6 IU vitamin E activity/g linoleate in 100 g adipose tissue fatty acids is tentatively suggested.

Dietary levels of vitamin E and polyunsaturated fatty acids and plasma vitamin E.

Seventeen daily diets (breakfast, lunch, and dinner) were analyzed from a 35-day menu cycle fed to students, under contract in the University dining halls. This 35-day menu cycle was repeated 6.6 times over the course of two 15-week semesters and registration and final examination periods. The average 2, 500 kcal diet collected during the sixth and seventh menu cycles contained 96 plus or minus 26 g fat of which 19.5 plus or minus 1.8% was linoleate and 28.7 plus or minus 14.2 mg total tocopherol of which 7.5 plus or minus 3.5 mg was RRR-alpha-tocopherol. Blood samples obtained from 26 female undergraduate student volunteers contained adequate levels of plasma total vitamin E, 1.09 plus or minus 0.25 mg/100 ml, despite the observation that 71% and 65% of the diets analyzed did not meet the value tabluated in the eighth edition of "Recommended Dietary Allowances" for adult females in terms of RRR-alpha-tocopherol or total vitamin E activity, respectively. These data emphasize the importance of the average long-term consumption of this fat-soluble vitamin rather than daily intake.

Fatty liver induction: inverse relationship between hepatic neutral lipid accumulation and dietary polyunsaturated fatty acids in orotic acid-fed rats.

The levels of hepatic neutral lipids in the orotic acid-fed rat were inversely related to the dietary levels of polyunsaturated fatty acids, as in the choline-deficient rat. Hepatic microsomal protein and phospholipid and total hepatic phospholipid were increased in orotic acid-induced fatty livers. The increase in phospholipid was largely restricted to the phosphatidylethanolamines.