Extracts of different sesame plant (Sesamum indicum) Linnaeus organs inhibited the in vitro growth of the fungus Leucocoprinus gongylophorus (Moller) (=Rozites gongylophora Moller), which is cultivated by the leaf-cutting ants of the species Atta sexdens rubropilosa Forel (Hymenoptera: Formicidae). The presence of the factor responsible for this inhibition was detected in methanol or chloroform extracts and is constant in the plant.
Abstract. Optimization of energy use by evolving organisms, predicted by theoretical extensions of the neo-Darwinian theory, is contrasted with that of irreversible thermodynamics, which predicts an increase in orderliness and thus an increase in energy consumption per unit of biomass. We compared this index with estimates of social complexity among ant genera and species. Our results show that simple optimization models cannot explain experimental data, and that social complexity correlates differently with negentropy at different levels of analysis. Comparing the genera among Formicidae, workers (not colonies) from genera with highly social species are less negentropic than those of socially primitive ones. At the sub-generic level, social complexity correlated positively with negentropy among species, for major workers in Acromyrmex and for minor workers in Atta. The results illustrate the complexity of thermodynamic criteria in the study of evolution but also hint at their usefulness. In this case, they show that two different evolutionary routes to the complex Attini ant societies may exist.Key words. Negentropy; oxygen consumption; social evolution; ants; energy; self-organization; dissipative systems.Several attempts to base the biological principle of evolution on physical laws include assumptions that natural selection has led to the optimization of living beings according to various criteria, such as average fitness 1, maximal efficiency in resource utilization 2, minimal metabolized energy per unit of biomass 3, maximum energetic power 4, minimal rate of entropy dissipation -s , etc. All these criteria assume that Darwin's principle translates into optimal regimes of operation along metabolic pathways in a biological system. This implies that evolution tends to make energy use by organisms more efficient and thus, all else being equal, energy consumption per unit mass should be reduced over evolutionary time. An opposing view derives from the approach put forward by the analysis of irreversible thermodynamics in self-organizing systems 5, which assumes an increase in order and thus in energy consumption per unit mass as a thermodynamic necessity of evolution 6. Nicolis and Prigogine 5 suggest that contact between irreversible thermodynamics and Darwin's idea of the survival of the fittest can probably be made because a low rate of dissipation is likely to give an organism a selective advantage. Lamprecht and Zotin 6, and especially Zotin et al. 7 9, work out the idea more carefully and conclude that the probability state for living organisms may be associated with the respiration intensity value. Only in the course of biological evolution have organisms with increasingly high levels of orderliness appeared step by step. Consequently, the dissipation function is related to the distance of the organism from equilibrium state. This theoretical contradiction allows for experiments which could eventually solve the problem if quantitative measures of order or of energy consumption are used to compare organis...
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