A fundamental but unanswered biological question asks how much energy, on average, Earth's different life forms spend per unit mass per unit time to remain alive. Here, using the largest database to date, for 3,006 species that includes most of the range of biological diversity on the planet-from bacteria to elephants, and algae to sapling trees-we show that metabolism displays a striking degree of homeostasis across all of life. We demonstrate that, despite the enormous biochemical, physiological, and ecological differences between the surveyed species that vary over 10 20 -fold in body mass, mean metabolic rates of major taxonomic groups displayed at physiological rest converge on a narrow range from 0.3 to 9 W kg ؊1 . This 30-fold variation among life's disparate forms represents a remarkably small range compared with the 4,000-to 65,000-fold difference between the mean metabolic rates of the smallest and largest organisms that would be observed if life as a whole conformed to universal quarterpower or third-power allometric scaling laws. The observed broad convergence on a narrow range of basal metabolic rates suggests that organismal designs that fit in this physiological window have been favored by natural selection across all of life's major kingdoms, and that this range might therefore be considered as optimal for living matter as a whole.allometry ͉ body size ͉ breathing ͉ scaling ͉ energy consumption T he process of life is critically dependent on consumption of energy from the environment. The amount of energy-per unit time per unit mass-required to sustain life can rightfully be considered one of the fundamental questions in biology. Yet a general quantitative answer to this question is lacking, despite the long history and the considerable number of studies devoted to various aspects of organismal energetics in all fields of bioscience. One reason for this persistent knowledge gap is that this fundamental question is typically approached in markedly different ways depending on the organisms being investigated. We show herein how differences in types, protocols, and units of measurements of metabolism have presented a challenge to the development of quantitative generalizations regarding the metabolic rates of organisms. We then use a comprehensive dataset to reconcile such differences and to characterize the remarkable similarity that emerges from comparisons of mass-specific metabolic rates across all of life. Problem SettingStudies of animal energetics have frequently focused on the allometric relationship between the whole-body metabolic rate Q and body mass M, Q ϭ Q 0 (M/M 0 ) b , where Q 0 is metabolic rate of an organism with body mass M 0 . Either M 0 or Q 0 can be chosen arbitrarily, whereas the second of these parameters is unambiguously defined by the choice of the first one. Usually, M 0 is chosen to be one mass unit-e.g., M 0 ϭ 1 g. For the mass-specific metabolic rate q ' Q/M, we have q ϭ q 0 (M/M 0 ) ␤ , ␤ ϭ b Ϫ 1, q 0 ϭ Q 0 /M 0 . Much of the current debate concerns the value of b, an...

Nonlinear dynamics and chaotic and complex systems constitute some of the most fascinating developments of late twentieth century mathematics and physics. The implications have changed our understanding of important phenomena in almost every field of science, including biology and ecology. This article investigates complexity and chaos in the spatiotemporal dynamics of aquatic ecosystems. The dynamics of these biological communities exhibit an interplay between processes acting on a scale from hundreds of meters to kilometers, controlled by biology, and processes acting on a scale from dozens to hundreds of kilometers, dominated by the heterogeneity of hydrophysical fields. We focus on how biological processes affect spatiotemporal pattern formation. Our results show that modeling by reaction-diffusion equations is an appropriate tool for investigating fundamental mechanisms of complex spatiotemporal plankton dynamics, fractal properties of planktivorous fish school movements, and their interrelationships.

Underlying the diversity of life and the complexity of ecology is order that re ects the operation of fundamental physical and biological processes. Power laws describe empirical scaling relationships that are emergent quantitative features of biodiversity. These features are patterns of structure or dynamics that are self-similar or fractal-like over many orders of magnitude. Power laws allow extrapolation and prediction over a wide range of scales. Some appear to be universal, occurring in virtually all taxa of organisms and types of environments. They offer clues to underlying mechanisms that powerfully constrain biodiversity. We describe recent progress and future prospects for understanding the mechanisms that generate these power laws, and for explaining the diversity of species and complexity of ecosystems in terms of fundamental principles of physical and biological science.Keywords: biodiversity; ecology; fractal; power law; scaling; self-similarity BACKGROUNDThe Earth's surface and the living things that inhabit it are incredibly diverse. The Earth presents an abiotic template of geology, physical oceanography and limnology, and climate that varies on a scale from the largest oceans, continents, lakes and rivers to the tiniest microsites. Billions of individual organisms belonging to millions of species are distributed over the Earth. They interact with each other and the abiotic environment on time-scales from microseconds to millennia and on spatial scales from a few micrometres to the entire globe. Underlying this enormous physical and biological diversity, however, are emergent patterns of ecological organization that are precise, quantitative, and universal or nearly so. Examples include the latitudinal, elevational and other gradients of species diversity, the way that species are aggregated into genera and higher taxonomic categories, the body sizes and relative abundances of coexisting species in ecological communities, the way that species diversity changes with sample area, and the successional changes in productivity, biomass and species composition and diversity following disturbance (Williams 1964;MacArthur 1972;Brown 1995).These emergent general features of ecological systems provide powerful clues about the underlying mechanisms that constrain ecological complexity and regulate biodiversity. On the one hand, the emergent patterns represent the * Author for correspondence (jhbrown@unm.edu).One contribution of 11 to a special Theme Issue 'The biosphere as a complex adaptive system'. outcome of the fundamental law-like processes of physics, chemistry and biology. Many of these mechanisms are well understood. They include thermodynamics, conservation of mass and energy, atomic particles and chemical elements, chemical stoicheiometry, geological tectonics and erosion, laws of biological inheritance, evolution by natural selection, and many others. It is obvious that they must play a role in regulating biodiversity. On the other hand, it is far from clear how these fundamental processes act an...

Power laws describing the dependence of metabolic rate on body mass have been established for many taxa, but not for prokaryotes, despite the ecological dominance of the smallest living beings. Our analysis of 80 prokaryote species with cell volumes ranging more than 1 000 000-fold revealed no significant relationship between mass-specific metabolic rate q and cell mass. By absolute values, mean endogenous mass-specific metabolic rates of non-growing bacteria are similar to basal rates of eukaryote unicells, terrestrial arthropods and mammals. Maximum mass-specific metabolic rates displayed by growing bacteria are close to the record tissue-specific metabolic rates of insects, amphibia, birds and mammals. Minimum mass-specific metabolic rates of prokaryotes coincide with those of larger organisms in various energy-saving regimes: sit-and-wait strategists in arthropods, poikilotherms surviving anoxia, hibernating mammals. These observations suggest a size-independent value around which the mass-specific metabolic rates vary bounded by universal upper and lower limits in all body size intervals.

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An understanding of allelic diversity and population structure is important in developing association studies and constructing core collections for tree breeding. We examined population genetic differentiation in the native Populus tomentosa by genotyping 460 unrelated individuals using 20 species-specific microsatellite markers. We identified 99 alleles with a mean of 4.95 observed alleles per locus, indicating a moderate level of polymorphism across all individuals. A model-based population structure analysis divided P. tomentosa into 11 subpopulations (K = 11). The pattern of individual assignments into the subsets (K = 3) provided reasonable evidence for treating climatic zones as genetic regions for population genetics. The highest level of genetic variation was found in the southern region (i.e., N = 93, N (P) = 11, H (E) = 0.445, F = -0.102), followed by the northeastern and northwestern regions. Thus, the southern region is probably the center of the current species distribution. No correlation was found between population genetic distance and geographic distance (r = 0.0855, P = 0.3140), indicating that geographical distance was not the principal factor influencing genetic differentiation in P. tomentosa. These data provide a starting point for conserving valuable natural resources and optimizing breeding programs.

Wood density is traditionally determined by a volumetric method that is accurate but expensive for large-scale sampling. A new device called the Resistograph was investigated for rapid assessment of relative wood density of live trees in progeny trials. Fourteen full-sib families of loblolly pine (Pinus taeda L.) produced by a six-parent half-diallel mating design were tested at four sites. For each family, wood density was measured with the traditional volumetric method and then compared with the Resistograph readings (amplitude). Amplitude had weak (0.29) to moderate (0.65) phenotypic correlations with wood density on an individual-tree basis over the four sites. The family mean correlation between the two measurements, however, was much stronger (0.92). The additive genetic correlation between the two measures was also high (0.95). Individual-tree breeding values of amplitude yielded more accurate rankings than phenotypic values. The rankings of the parental, general-combining abilities were identical for the two measures. Both wood density and amplitude were under strong genetic control at the family level (full-sib family heritability (h2fs) = 0.95 for wood density and h2fs = 0.85 for amplitude). The efficiency of using the Resistograph as a means of indirect selection for improvement of wood density was 87% at the family level. Results from this study suggest that the Resistograph could be used reliably and efficiently to assess relative wood density of live trees for selection in tree improvement programs. The method is rapid, nondestructive, and much cheaper than the traditional volumetric method.

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