Is there a general theory of community ecology?

Community ecology entered the 1970s with the belief that niche theory would supply a general theory of community structure. The lack of wide-spread empirical support for niche theory led to a focus on models specific to classes of communities such as lakes, intertidal communities, and forests. Today, the needs of conservation biology for metrics of “ecological health” that can be applied across types of communities prompts a renewed interest in the possibility of general theory for community ecology. Disputes about the existence of general patterns in community structure trace at least to the 1920s and continue today almost unchanged in concept, although now expressed through mathematical modeling. Yet, a new framework emerged in the 1980s from findings that community composition and structure depend as much on the processes that bring species to the boundaries of a community as by processes internal to a community, such as species interactions and co-evolution. This perspective, termed “supply-side ecology”, argued that community ecology was to be viewed as an “organic earth science” more than as a biological science. The absence of a general theory of the earth would then imply a corresponding absence of any general theory for the communities on the earth, and imply that the logical structure of theoretical community ecology would consist of an atlas of models special to place and geologic time. Nonetheless, a general theory of community ecology is possible similar in form to the general theory for evolution if the processes that bring species to the boundary of a community are analogized to mutation, and the processes that act on the species that arrive at a community are analogized to selection. All communities then share some version of this common narrative, permitting general theorems to be developed pertaining to all ecological communities. Still, the desirability of a general theory of community ecology is debatable because the existence of a general theory suppresses diversity of thought even as it allows generalizations to be derived. The pros and cons of a general theory need further discussion.     

Plant ecology. * Schulze ED, Beck E, Muller-Hohenstein K. 2005. Berlin/Heidelberg: Springer. $89{middle dot}95 (hardback). 702 pp.

This book (a translation fromSchulze et al., 2002) is one of the most comprehensive textbooksof plant ecology so far. The authors aim to ‘for the firsttime bring together and clearly organize the large subdisciplinesof plant ecology’ and, to a large extent they have succeeded.The book is well written, and its more than 500 illustrationsare beautifully laid out and well chosen to help the readerunderstand the theory. It is clearly suitable not only     

Human Ecology for Introductory Biology Courses: An Overview

Human ecology, specifically the population—resource—environmentdilemma, should be given thorough coverage in every introductorybiology course. To aid educators in integrating it into thecourse, the subject is outlined here and suggestions are givenon what topics should be emphasized and how they might be introducedto students. Special attention is given to the fundamental roleof population growth in the dilemma, and to the complex interactionsamong population growth, depletion of resources, and environmentaldeterioration. Today's human population size appears to be abovethe long-term carrying capacity of Earth, and is only maintained(albeit often badly) by the exploitation of a "one-time bonanza"of fertile soils, fossil fuels, concentrated ores, ground water,and other species of organisms. If current trends continue,the depletion of these resources will progressively degradethe human environment, destroying the capacity ofnatural ecosystemsto supply civilization with indispensible services. The resultswill be in increasing frequency and severity of disasters, especiallyfamines, that will at first most seriously affect the poor.But the rich will increasingly be impoverished, and be engulfedalso. The basic solution to the dilemma is reduction of thesize of the human population to one well below the long-termcarrying capacity (one living on resource "income" rather than"capital") and establishing an equitable society with a sustainableeconomic system.     

Food-web studies in shallow eutrophic lakes by the Netherlands Institute of Ecology: Main results,knowledge gaps and new perspectives

For more than 20 years scientists of the ‘Food-chain studies’ Group of the former Limnological Institute have been studying interactions within the pelagic food web. Purpose of research was to explain the structure and dynamics of the zooplankton and fish communities in lakes and reservoirs in relation to biotic and abiotic environmental factors. A so-called multi-species approach was used, in which all common and abundant species within a specific ecosystem were studied on the individual and population level with the same degree of detail. The recent results and the scientific approach used are evaluated and the main gaps in knowledge about food-web dynamics in shallow eutrophic lakes are identified and discussed. It is concluded that instead of the purely functional approach used so far, future studies should also include evolutionary aspects which determine the success of an organism in a given environment and that more attention should be paid to central questions in ‘community ecology’. This paper is based on a lecture given by the first author for the Netherlands Society of Aquatic Ecology on May 12th, 1992, in Amsterdam, The Netherlands.     

Individuals,populations and the balance of nature: the question of persistence in ecology

Explaining the persistence of populations is an important quest in ecology, and is a modern manifestation of the balance of nature metaphor. Increasingly, however, ecologists see populations (and ecological systems generally) as not being in equilibrium or balance. The portrayal of ecological systems as “non-equilibrium” is seen as a strong alternative to deterministic or equilibrium ecology, but this approach fails to provide much theoretical or practical guidance, and warrants formalisation at a more fundamental level. This is available in adaptation theory, which allows population persistence to be explained as an epiphenomenon stemming from the maintenance, survival, movement and reproduction of individual organisms. These processes take place within a physicochemical and biotic environment that persists through structured annual cycles, but which is also spatiotemporally dynamic and subject to stochastic variation. The focus is thus shifted from the overproduction of offspring and the consequent density dependent population pressure thought to follow, to the adaptations and ecological circumstances that support those relatively few individuals that do survive.     

Neutral theory in community ecology

One of the central goals of community ecology is to understand the forces that maintain species diversity within communities. The traditional niche-assembly theory asserts that species live together in a community only when they differ from one another in resource uses. But this theory has some difficulties in explaining the diversity often observed in specie-rich communities such as tropical forests. As an alternative to the niche theory, Hubbell and other ecologists introduced a neutral model. Hubbell argues that the number of species in a community is controlled by species extinction and immigration or speciation of new species. Assuming that all individuals of all species in a trophically similar community are ecologically equivalent, Hubbell’s neutral theory predicts two important statistical distributions. One is the asymptotic log-series distribution for the metacommunities under point mutation speciation, and the other is the zero-sum multinomial distribution for both local communities under dispersal limitation and metacommunities under random fission speciation. Unlike the niche-assembly theory, the neutral theory takes similarity in species and individuals as a starting point for investigating species diversity. Based on the fundamental processes of birth, death, dispersal and speciation, the neutral theory provided the first mechanistic explanation of species abundance distribution commonly observed in natural communities. Since the publication of the neutral theory, there has been much discussion about it, pro and con. In this paper, we summarize recent progress in the assumption, prediction and speciation mode of the neutral theory, including progress in the theory itself, tests about the assumption of the theory, prediction and speciation mode at the metacommunity level. We also suggest that the most important task in the future is to bridge the niche-assembly theory and the neutral theory, and to add species differences to the neutral theory and more stochasticity to the niche theory. __________ Translated from Journal of Plant Ecology, 2006, 30(5): 868–877 [译自:植物生态学报]     

Trait plasticity in species interactions: a driving force of community dynamics

Evolutionary community ecology is an emerging field of study that includes evolutionary principles such as individual trait variation and plasticity of traits to provide a more mechanistic insight as to how species diversity is maintained and community processes are shaped across time and space. In this review we explore phenotypic plasticity in functional traits and its consequences at the community level. We argue that resource requirement and resource uptake are plastic traits that can alter fundamental and realised niches of species in the community if environmental conditions change. We conceptually add to niche models by including phenotypic plasticity in traits involved in resource allocation under stress. Two qualitative predictions that we derive are: (1) plasticity in resource requirement induced by availability of resources enlarges the fundamental niche of species and causes a reduction of vacant niches for other species and (2) plasticity in the proportional resource uptake results in expansion of the realized niche, causing a reduction in the possibility for coexistence with other species. We illustrate these predictions with data on the competitive impact of invasive species. Furthermore, we review the quickly increasing number of empirical studies on evolutionary community ecology and demonstrate the impact of phenotypic plasticity on community composition. Among others, we give examples that show that differences in the level of phenotypic plasticity can disrupt species interactions when environmental conditions change, due to effects on realized niches. Finally, we indicate several promising directions for future phenotypic plasticity research in a community context. We need an integrative, trait-based approach that has its roots in community and evolutionary ecology in order to face fast changing environmental conditions such as global warming and urbanization that pose ecological as well as evolutionary challenges.     

From dispersal to landscapes: progress in the understanding of population dynamics

The development of our understanding of population dynamics over the past 50 years is reviewed from a personal perspective. An early emphasis on population vital rates was superceded by recognition of the importance of the specific community context of focal populations, and most recently has in turn been enriched by a landscape perspective. Certain basic principles are outlined including the value of a systems context for population analyses, the power of a dual mechanistic and contextual perspective, and the inevitability of density control in a finite biosphere. Numbers are determined by the balance of two complex parameters:p — the per capita growth promoting (enhancing) forces, ands — the per capita growth suppressing forces. Multiple factor explanations of demographic behavior are therefore to be expected, as well as temporal and spatial variations in them. An appreciation for the potential role of dispersal as a population vital rate led to the development of metapopulation theory. A renewed understanding of the role of community context in population dynamics provoked the realization that a multi-factor approach was required. This in turn allowed us to reconcile the reality of local demographic complexity with global generalizations. Finally, the introduction of landscape ecology into demographic thinking added many new insights. It is now appreciated that a spatially explicit mosaic of habitat patches, edge effects, corridors, and even the proportion of favorable to marginal habitats can all be critically important factors in influencing population dynamics.     

Darwinism as a constraint of ecological pluralism

In his respond to critical remarks of Mirkin (2003), the author claims that pluralism in ecology is not only its strength but also a weakness. Contemporary ecology became less pluralistic and this can be considered as good sign of maturing science. Ecological pluralism can be exemplified by the coexistence in 1920-30s of two different approaches to plant community: that of Frederic Clements in USA and that of Josias Braun-Blanquet in France. However the way to progress in this branch of ecology was paved rather by heretical ideas of Henry Gleason in USA and Ramensky in Russia (both authors independently developed non-holistic view of community as an assemblage of individualistically distributed species) than by "peaceful" coexistence of well-established schools, representatives of which tried not to interfere into argumentation of each other. Notable success in ecology of last decades was connected with several new methodologies, e.g. macroecology that concerned large scale of space and time. However Darwinism in its attempt to explain the order of nature referring to its origin remains the most universal and fruitful methodology of ecology. The success of Darwinism in ecology is understandable because this generalizing theory is based on the same universal principles that underlie the survival of any population. Ecologists and evolutionary biologists trying to understand various natural patterns actually deal with the same fundamental laws, i.e. exponential population growth, limitation of this growth by resource shortage and/or press of predators, the existence of individual variability in survival, etc.     

The ecology of seeds. * Fenner M, Thompson K. 2005. Cambridge: Cambridge University Press. {pound}26 (softback) {pound}55 (hardback) 260 pp.

This volume is a timely updateand considerable expansion of the small book Seed Ecology, publishedby the first author twenty years ago, and long out of print. Is it useful to separate a particular branch of study such as‘seed ecology’ from the wider field of plant ecology?Aren't seeds just a particular packaged form of the sporophyte,at a certain stage in its life cycle? While some may ask thosequestions, a major strength of this book is the care that theauthors take throughout to set their review in the context ofcurrent ecological     

Running on empty: recharge dynamics from animal movement data

Vital rates such as survival and recruitment have always been important in the study of population and community ecology. At the individual level, physiological processes such as energetics are critical in understanding biomechanics and movement ecology and also scale up to influence food webs and trophic cascades. Although vital rates and population‐level characteristics are tied with individual‐level animal movement, most statistical models for telemetry data are not equipped to provide inference about these relationships because they lack the explicit, mechanistic connection to physiological dynamics. We present a framework for modelling telemetry data that explicitly includes an aggregated physiological process associated with decision making and movement in heterogeneous environments. Our framework accommodates a wide range of movement and physiological process specifications. We illustrate a specific model formulation in continuous‐time to provide direct inference about gains and losses associated with physiological processes based on movement. Our approach can also be extended to accommodate auxiliary data when available. We demonstrate our model to infer mountain lion (Puma concolor; in Colorado, USA) and African buffalo (Syncerus caffer; in Kruger National Park, South Africa) recharge dynamics.     

On the Evolution of the Timing of Reproduction with Non-equilibrium Resident Dynamics

We study the evolution of an individual’s reproductive strategy in a mechanistic modeling framework. We assume that the total number of juveniles one adult individual can produce is a finite constant, and we study how this number should be distributed during the season, given the types of inter-individual interactions and mortality processes included in the model. The evolution of the timing of reproduction in this modeling framework has already been studied earlier in the case of equilibrium resident dynamics, but we generalize the situation to also fluctuating population dynamics. We find that, as in the equilibrium case, the presence or absence of inter-juvenile aggression affects the functional form of the evolutionarily stable reproductive strategy. If an ESS exists, it can have an absolutely continuous part only if inter-juvenile aggression is included in the model. If inter-juvenile aggression is not included in the model, an ESS can have no continuous parts, and only Dirac measures are possible.     

Understanding evolutionary and ecological dynamics using a continuum limit

Continuum limits in the form of stochastic differential equations are typically used in theoretical population genetics to account for genetic drift or more generally, inherent randomness of the model. In evolutionary game theory and theoretical ecology, however, this method is used less frequently to study demographic stochasticity. Here, we review the use of continuum limits in ecology and evolution. Starting with an individual‐based model, we derive a large population size limit, a (stochastic) differential equation which is called continuum limit. By example of the Wright–Fisher diffusion, we outline how to compute the stationary distribution, the fixation probability of a certain type, and the mean extinction time using the continuum limit. In the context of the logistic growth equation, we approximate the quasi‐stationary distribution in a finite population.     

Community ecology: is it time to move on? (An American Society of Naturalists presidential address)

Because of the contingency and complexity of its subject matter, community ecology has few general laws. Laws and models in community ecology are highly contingent, and their domain is usually very local. This fact does not mean that community ecology is a weak science; in fact, it is the locus of exciting advances, with growing mechanistic understanding of causes, patterns, and processes. Further, traditional community ecological research, often local, experimental, and reductionist, is crucial in understanding and responding to many environmental problems, including those posed by global changes. For both scientific and societal reasons, it is not time to abandon community ecology.     

Plant roots. Growth, activity and interaction with soils

It is (or should be) self-evident that life on Earth dependsmainly on life in earth, and in this respect soil–plantinteractions are of key importance. This book brings togetherareas that are still often compartmented into fields such aschemical and physical aspects of soil science (where plantsare still sometimes regarded as a ‘black box’ ofuncertain relevance), plant physiology (now sometimes re-badgedas plant functional biology), and soil microbial ecology. Agriculturalscientists have, of course, rarely been guilty of ignoring soilfactors in relation to plant growth and productivity. Plantecologists sometimes have, and to some of them it's the soilthat is the ‘black box’ when it comes to understandingplant population and community ecology. Models of the     

Networks in ecology

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Recently, ecology has shown a strong interest in network theory. The question, as with any other emerging field, is to what extent we are making real progress in understanding ecological and evolutionary processes or just telling the same stories with fancy new words. I first present a biased overview of the development of network theory, focusing on its search for common patterns across seemingly different systems. I then proceed by discussing some applications of network theory in ecology, namely, species interactions, spatial ecology, epidemiology, and evolution in social groups . Finally, I suggest important contributions of the network approach such as identifying the consequences of heterogeneity for population and community dynamics, potential pitfalls, and future directions.     

Interspecific allometry of population density in mammals and other animals: the independence of body mass and population energy-use

Global regressions of ecological population densities on body mass for mammals and for terrestrial animals as a whole show that local population energy-use is approximately independent of adult body mass—over a body mass range spanning more than 11 orders of magnitude. This independence is represented by the slope of the regressions approximating –0.75, the reciprocal of the way that individual metabolic requirements scale with body mass. The pattern still holds for mammalian primary consumers when the data are broken down by geographic area, by broad habitat-type and by individual community. Slopes for mammalian secondary consumers are also not statistically distinguishable from –0.75. For any given body mass temperate herbivores maintain on average population densities of 1.5 to 2.0 times those of tropical ones, though slopes do not differ. Terrestrial animals of all sizes exhibit approximately the same range of population energy-use values. These results agree with those reported for population energy-budgets. It is suggested that rough independence of body mass and the energy-use of local populations is a widespread rule of animal ecology and community structure.     

Island biogeography and the reproductive ecology of great tits Parus major

Island biogeography theory has contributed greatly to both theoretical and applied studies of conservation biology (e.g., design of nature reserves, minimum viable population sizes, extinction risk) and community composition. However, little theoretical and empirical work has addressed how island isolation and size affect reproductive ecology. We investigated the reproductive ecology of great tits (Parus major) on one offshore and one nearshore island, as well as on the Danish mainland. Tits breeding on the offshore island bred later, laid smaller clutches, and laid larger eggs than those on the nearshore island and mainland. In addition, the level of ectoparasite infestation in nests was highest on the offshore island, intermediate on the nearshore island, and lowest on the mainland. These insular effects may occur due to lower food abundance on islands, to density-dependent effects, or to effects related to low genetic diversity within island populations. Whatever the cause, the results emphasize that future studies of forest fragmentation/population isolation should consider not only gross measures of reproductive success, but also fine-scale measures such as clutch size, timing of breeding, and parasite prevalence. Received: 10 November 1997 / Accepted: 9 March 1998