Fundamental Ecological Concepts Research Articles

W. S. Cooper As I Knew Him: Teacher, Mentor and Friend

W. S. Cooper As I Knew Him: Teacher, Mentor and Friend

Resolution of Respect: Paul Risser, 1939–2014

Resolution of Respect: Paul Risser, 1939–2014

The community ecology of microbial molecules.

The community ecology of microbial molecules.

Cambronne, A.2013. Deerland: America's Hunt for Ecological Balance and the Essence of Wildness. Lyons Press, Guileford, Conneticut, 272 pp. ISBN 978-0-7627-8027-3, price (paper), $18.95

A. Cambronne 2013. Deerland: America's Hunt for Ecological Balance and the Essence of Wildness. Lyons Press, Guileford, Conneticut, 272 pp. ISBN 978-0-7627-8027-3, price (paper), $18.95. The deer family consists of some 40 species spanning 5 continents. Cervids are incredibly diverse in body size, behavior, and habitat use, and scientific research on cervids has provided groundbreaking insight into fundamental concepts in ecology and evolution (e.g., Isle of Rum Red Deer Project). Cervids play a critical role in shaping regional ecosystems and are a major food source for a variety of predators. Some of their ecological impacts, however, are undesirable from our vantage point, and we , in fact, are among their top predators: Deerland is focused on these aspects, and takes the reader on a tour across North America exploring the ecological, economic, and social ramifications of humanity's relationship (or in Cambronne's view, obsession), with deer. More specifically, Deerland is about white-tailed deer, Odocoileus virginianus . The species numbers around 25 million (precise estimates are hard to come by) and is distributed across much of North America. White-tailed deer are the most popular …

Commensalism: A Fundamental Concept in Ecology?

Similar to “parasitism” and “mutualism”, the concept of commensualism defines a kind of biological association, i.e. the neutral interaction between two different species. This paper shows that “commensualism” was initially defined by the Belgian zoologist and parasitologist Pierre-Joseph van Beneden (1809–1894) as referring to biological associations between organic individuals from different species. According to van Beneden, one individual derives biological advantages from this kind of association, whereas the other one remains neutral, i.e. does not receive any biological loss or gain. Tracing the further history of the concept, the paper demonstrates that, while “commensalism” was initially created and used in zoology, it was taken up in other biological disciplines shortly afterward, such as botany and the emerging field of ecology. However, the experimental demonstration of the phenomenon of commensualism remained difficult. This, in turn, contributed to the nomadic existence of this concept in the life sciences of the twentieth century.

Neutral communities in fragmented landscapes

Habitat fragmentation displays a crucial role in conservation biology. Despite this, little is known about the detailed ecological consequences of habitat fragmentation due to the scarce number of controlled experimental surveys. The species–area relationship, a fundamental concept in ecology, requires the understanding of the fragmentation effects in a long term perspective, which turns this task even harder. Here we address the spatial patterns of species distribution in fragmented landscapes, assuming a neutral community model. We study the species area relationship and how its shape changes as the landscape becomes more fragmented. Recent investigations, based on extensive computer simulation, have contributed to establish some definite conclusions in the study of non‐fragmented landscapes: the existence of a three‐regime or two‐regime scenario for the species–area relationship, the emergence of a power‐law regime at intermediate scales and the augment of the species–area exponent z with the speciation rate. Despite the recent efforts, some other questions remain, such as the dependence of z in the whole range of the speciation rate. Questions like these are currently debated but generalizations cannot be drawn. This is the first paper, to our knowledge, that uses the coalescence method and neutral theory to examine biodiversity on more complex spatial structures. Our simulation results corroborate that the fragmentation plays a crucial role in shaping the species–area relationship, by determining the existence and extension of the power‐law regime associated with small and intermediate areas. On the other hand, when individuals are allowed to disperse over longer distances the species–area relationship now displays the classic triphasic pattern, and the intermediate regime, which is well described by a power‐law, is established even for highly fragmented landscapes.

The role of body mass in diet contiguity and food-web structure.

1. The idea that species occupy distinct niches is a fundamental concept in ecology. Classically, the niche was described as an n-dimensional hypervolume where each dimension represents a biotic or abiotic characteristic. More recently, it has been hypothesised that a single dimension may be sufficient to explain the system-level organization of trophic interactions observed between species in a community. 2. Here, we test the hypothesis that species body mass is that single dimension. Specifically, we determine how the intervality of food webs ordered by body size compares to that of randomly ordered food webs. We also extend this analysis beyond the community level to the effect of body mass in explaining the diets of individual species. 3. We conclude that body mass significantly explains the ordering of species and the contiguity of diets in empirical communities. 4. At the species-specific level, we find that the degree to which body mass is a significant explanatory variable depends strongly on the phylogenetic history, suggesting that other evolutionarily conserved traits partly account for species' roles in the food web. 5. Our investigation of the role of body mass in food webs thus helps us to better understand the important features of community food-web structure and the evolutionary forces that have led us to the communities we observe.

Imaginary populations

A few years ago, Camus & Lima (2002) wrote an essay to stimulate ecologists to think about how we define and use a fundamental concept in ecology: the population. They concluded, concurring with Berryman (2002), that a population is ‘a group of individuals of the same species that live together in an area of sufficient size to permit normal dispersal and/or migration behaviour and in which population changes are largely the results of birth and death processes’. They pointed out that ecologists often forget ‘to acknowledge that many study units are neither natural nor even units in terms of constituting a population system’, and hence claimed that we ‘require much more accuracy than in past decades in order to be more effective to characterize populations and predict their behaviour’. They stated that this is especially necessary ‘in disciplines such as conservation biology or resource pest management, to avoid reaching wrong conclusions or making inappropriate decisions’. As a population ecologist and conservation biologist I totally agree with these authors and, like them, I believe that greater precision and care is needed in the use and definition of ecological terms. The point I wish to stress here is that we ecologists tend to forget that when we use statistical tools to infer results from our sample to a population we work with what statisticians term ‘imaginary’, ‘hypothetical’ or ‘potential’ popula-tions. As Zar (1999) states, if our sample data consist of 40 measurements of growth rate in guinea pigs “the population about which conclusions might be drawn is the growth rates of all the guinea pigs that conceivably might have been administered the same food supplement under identical conditions”. Such a population does not really exist, and hence it is considered a hypothetical or imaginary population. Compare that definition with the population concept that would be in our minds when performing such measurements. We would probably assume that our study population consisted of pigs (not the growth rates of pigs!) and probably all the pigs at the farm we were sampling, rather than the all the growth rates of the pigs that might conceivably have been administered the same food. We overlook the fact that we are using the statistical tools to try to estimate ecological population para-meters (and test specific hypotheses on the values of these population parameters) but that the ecological population which is in our minds and the statistical (imaginary) population of our tests need not necessarily be the same (and most often are not). So, to avoid wrong inferences (with wide-ranging consequences if we are dealing with decision-making processes) we should do all we possibly can to ensure that our natural populations are as similar as possible to the imaginary populations of statisticians, or at least we should discuss our results within the framework in which our inference was developed. Statistics is not an ad hoc tool invented for us, but rather a tool that we have borrowed from statisticians for our purposes. We should always keep this in mind.

Profiling ecosystem vulnerability to invasion by zebra mussels with support vector machines

Decades since the initial establishment of zebra mussels (Dreissena polymorpha) in North America, understanding and controlling the invasion of aquatic ecosystems continues to be a problem in continent-wide conservation and landscape management. While the high economic and conservation burden of this species makes accurate predictions of future invasions a research priority, forecasting is confounded by limited data, tenuous model assumptions, and the stochasticity of the invasion process. Using a new method for niche identification, we profiled invasion vulnerability for 1,017 lakes in the Great Lakes region of the Unites States. We used a nonparametric geoadditive regression model to test for effects of two water quality variables on the present distribution of zebra mussels. We then used the support vector data description (SVDD), a support vector machine for one-class classification, to estimate the boundary of the ecological niche. By disentangling niche estimation from distributional assumptions, computational niche models could be used to test an array of fundamental concepts in ecology and evolution, while species invasions forecasting is representative of the wide range of potential applications for niche identification in conservation and management.

Patterns and Scales in Gastrointestinal Microbial Ecology

The body surfaces of humans and other animals are colonized at birth by microorganisms. The majority of microbial residents on the human body exist within gastrointestinal (GI) tract communities, where they contribute to many aspects of host biology and pathobiology. Recent technological advances have expanded our ability to perceive the membership and physiologic traits of microbial communities along the GI tract. To translate this information into a mechanistic and practical understanding of host-microbe and microbe-microbe relationships, it is necessary to recast our conceptualization of the GI tract and its resident microbial communities in ecological terms. This review depicts GI microbial ecology in the context of 2 fundamental ecological concepts: (1) the patterns of biodiversity within the GI tract and (2) the scales of time, space, and environment within which we perceive those patterns. We show how this conceptual framework can be used to integrate our existing knowledge and identify important open questions in GI microbial ecology.

A keystone predator controls bacterial diversity in the pitcher‐plant (Sarracenia purpurea) microecosystem

The community of organisms inhabiting the water-filled leaves of the carnivorous pitcher-plant Sarracenia purpurea includes arthropods, protozoa and bacteria, and serves as a model system for studies of food web dynamics. Despite the wealth of data collected by ecologists and zoologists on this food web, very little is known about the bacterial assemblage in this microecosystem. We used terminal restriction fragment length polymorphism (T-RFLP) analysis to quantify bacterial diversity within the pitchers as a function of pitcher size, pH of the pitcher fluid and the presence of the keystone predator in this food web, larvae of the pitcher-plant mosquito Wyeomyia smithii. Results were analysed at two spatial scales: within a single bog and across three isolated bogs. Pitchers were sterile before they opened and composition of the bacterial assemblage was more variable between different bogs than within bogs. Measures of bacterial richness and diversity were greater in the presence of W. smithii and increased with increasing pitcher size. Our results suggest that fundamental ecological concepts derived from macroscopic food webs can also be used to predict the bacterial assemblages in pitcher plants.

Parasites entangled in food webs

Food webs are a fundamental concept in ecology in which parasites have been virtually ignored. In a recent article, Lafferty et al. address this imbalance, finding that the inclusion of parasites in food webs could be of greater importance to ecosystem stability than was previously thought. Furthermore, the bottom of the food chain is perhaps no longer the most dangerous place to be.

Chemical and biological trends during lake evolution in recently deglaciated terrain.

As newly formed landscapes evolve, physical and biological changes occur that are collectively known as primary succession. Although succession is a fundamental concept in ecology, it is poorly understood in the context of aquatic environments. The prevailing view is that lakes become more enriched in nutrients as they age, leading to increased biological production. Here we report the opposite pattern of lake development, observed from the water chemistry of lakes that formed at various times within the past 10,000 years during glacial retreat at Glacier Bay, Alaska. The lakes have grown more dilute and acidic with time, accumulated dissolved organic carbon and undergone a transient rise in nitrogen concentration, all as a result of successional changes in surrounding vegetation and soils. Similar trends are evident from fossil diatom stratigraphy of lake sediment cores. These results demonstrate a tight hydrologic coupling between terrestrial and aquatic environments during the colonization of newly deglaciated landscapes, and provide a conceptual basis for mechanisms of primary succession in boreal lake ecosystems.

Dung-Inhabiting Fungi in the High School Biology Laboratory

It may seem to be an unlikely laboratory subject for a high school biology class, but the study of dung-inhabiting or coprophilous fungi can provide many rewarding activities that illustrate basic lab techniques and fundamental ecological concepts. The setup is inexpensive, easy to initiate and maintain, and provides many opportunities for refinement and development of new experiments. Dung samples incubated in a moist, covered container exposed to indirect light should support the growth of coprophilous fungi for at least several weeks. Numerous dung sources are possible, with common herbivorous mammals such as horses, cattle, sheep, rabbits and deer being the most accessible and productive. Dung collected from animals in the wild often provides the most diverse communities of fungi, but domesticated animals can also be used, especially if they are fed natural herbage. Dung can be collected ahead, particularly if travel brings the teacher or the student to a distant area with different animals. In this case, samples should be air-dried, put in air-tight containers, and kept in a cool place until water is added to activate spore germination. Small animals can be trapped, or pets can be fed natural herbage, so dung samples collected in captivity. Collection and incubation of the dung of carnivorous animals is not recommended, as these animals are likely to harbor the spores of fungi and various stages of invertebrate parasites potentially pathogenic to humans. The information on fungi associated with

How the Tail Wags the Dog: How Value Judgments Determine Ecological Science

Philosophers, policymakers, and scientists have long asserted that ecological science – and especially notions of homeostasis, balance, or stability – help to determine environmental values and to supply imperatives for environmental ethics and policy. We argue that this assertion is questionable. There are no well developed general ecological theories having predictive power, and fundamental ecological concepts, such as ‘community’ and ‘stability’, are used in inconsistent and ambiguous ways. As a consequence, the contribution of ecology to environmental ethics and values lies more in the realm of natural history and case studies than in the realm of general theory. Moreover, although general ecological theory is unable to contribute to environmental values in the way many philosophers and policymakers have hoped, environmental values can and do contribute to ecological hypotheses and methods. Using examples related to preservation versus development, hunting versus animal rights, and controversies over pest control, we show that, because ecology is conceptually and theoretically underdetermined, environmental values often influence the practice of ecological science.

How the Tail Wags the Dog: How Value Judgments Determine Ecological Science

Philosophers, policymakers, and scientists have long asserted that ecological science – and especially notions of homeostasis, balance, or stability – help to determine environmental values and to supply imperatives for environmental ethics and policy. We argue that this assertion is questionable. There are no well developed general ecological theories having predictive power, and fundamental ecological concepts, such as ‘community’ and ‘stability’, are used in inconsistent and ambiguous ways. As a consequence, the contribution of ecology to environmental ethics and values lies more in the realm of natural history and case studies than in the realm of general theory. Moreover, although general ecological theory is unable to contribute to environmental values in the way many philosophers and policymakers have hoped, environmental values can and do contribute to ecological hypotheses and methods. Using examples related to preservation versus development, hunting versus animal rights, and controversies over pest control, we show that, because ecology is conceptually and theoretically underdetermined, environmental values often influence the practice of ecological science.

Genetic Diversity of Bacteria along a Stream Continuum

Adaptation is a fundamental concept in ecology and evolution. Determining whether organisms are adapted requires genetic analysis of the organism. We characterized the genetic structure of isolates of two species of aquatic bacteria (Pseudomonas cepacia and P. pickettii) using starch gel electrophoresis to determine the relationship between genetic diversity and stream location. Genetic diversity in these species of bacteria did not change longitudinally. However, each location in the stream had genetically unique bacteria. Genetic distance among isolates was found to be related to geographical distance, i.e., isolates farther apart in the stream were more genetically dissimilar. The results suggest localized adaptation. Soil forms of P. cepacia collected from the same catchment were very different genetically from the aquatic forms of the same species. Analyzing patterns of allozymes may be of value in determining the source of bacteria in aquatic ecosystems.