In ecology, the competitive exclusion principle, sometimes referred to as Gause's law, is a proposition that two species which compete for the same limited resource cannot coexist at constant population values. When one species has even the slightest advantage over another, the one with the advantage will dominate in the long term. This leads either to the extinction of the weaker competitor or to an evolutionary or behavioral shift toward a different ecological niche. The principle has been paraphrased in the maxim "complete competitors cannot coexist".
The intermediate disturbance hypothesis (IDH) suggests that local species diversity is maximized when ecological disturbance is neither too rare nor too frequent. At low levels of disturbance, more competitive organisms will push subordinate species to extinction and dominate the ecosystem. At high levels of disturbance, due to frequent forest fires or human impacts like deforestation, all species are at risk of going extinct. According to IDH theory, at intermediate levels of disturbance, diversity is thus maximized because species that thrive at both early and late successional stages can coexist. IDH is a nonequilibrium model used to describe the relationship between disturbance and species diversity. IDH is based on the following premises: First, ecological disturbances have major effects on species richness within the area of disturbance. Second, interspecific competition results in one species driving a competitor to extinction and becoming dominant in the ecosystem. Third, moderate ecological scale disturbances prevent interspecific competition.
Species richness, or biodiversity, increases from the poles to the tropics for a wide variety of terrestrial and marine organisms, often referred to as the latitudinal diversity gradient. The latitudinal diversity gradient is one of the most widely recognized patterns in ecology. It has been observed to varying degrees in Earth's past. A parallel trend has been found with elevation, though this is less well-studied.
Source–sink dynamics is a theoretical model used by ecologists to describe how variation in habitat quality may affect the population growth or decline of organisms.
Ecological forecasting uses knowledge of physics, ecology and physiology to predict how ecological populations, communities, or ecosystems will change in the future in response to environmental factors such as climate change. The goal of the approach is to provide natural resource managers with information to anticipate and respond to short and long-term climate conditions.
In ecology, a priority effect refers to the impact that a particular species can have on community development as a result of its prior arrival at a site. There are two basic types of priority effects: inhibitory and facilitative. An inhibitory priority effect occurs when a species that arrives first at a site negatively affects a species that arrives later by reducing the availability of space or resources. In contrast, a facilitative priority effect occurs when a species that arrives first at a site alters abiotic or biotic conditions in ways that positively affect a species that arrives later. Inhibitory priority effects have been documented more frequently than facilitative priority effects. Studies indicate that both abiotic and biotic factors can affect the strength of priority effects.. Priority effects are a central and pervasive element of ecological community development that have significant implications for natural systems and ecological restoration efforts.
The term phylogenetic niche conservatism has seen increasing use in recent years in the scientific literature, though the exact definition has been a matter of some contention. Fundamentally, phylogenetic niche conservatism refers to the tendency of species to retain their ancestral traits. When defined as such, phylogenetic niche conservatism is therefore nearly synonymous with phylogenetic signal. The point of contention is whether or not "conservatism" refers simply to the tendency of species to resemble their ancestors, or implies that "closely related species are more similar than expected based on phylogenetic relationships". If the latter interpretation is employed, then phylogenetic niche conservatism can be seen as an extreme case of phylogenetic signal, and implies that the processes which prevent divergence are in operation in the lineage under consideration. Despite efforts by Jonathan Losos to end this habit, however, the former interpretation appears to frequently motivate scientific research. In this case, phylogenetic niche conservatism might best be considered a form of phylogenetic signal reserved for traits with broad-scale ecological ramifications. Thus, phylogenetic niche conservatism is usually invoked with regards to closely related species occurring in similar environments.
Catherine H. Graham is an American team leader and senior scientist working on the Biodiversity & Conservation Biology, and the Spatial Evolutionary Ecology research units at the Swiss Federal Institute for Forest, Snow and Landscape Research WSL. From 2003 to 2017 she was an Assistant, Associate, or Full Professor of Ecology and Evolution at the Stony Brook University, and since her appointment at the WSL in 2017 she has maintained adjunct status there. She received both her M.S. degree (1995) and her Ph.D. (2000) from the University of Missouri at St. Louis, and did post-doctoral training at the Jet Propulsion Laboratory and the University of California, Berkeley. She studies biogeography, conservation biology, and ecology. Catherine H. Graham is most noted for her analysis of statistical models to describe species' distributions. This work with Jane Elith is useful in determining changes in biodiversity resulting from human activities. Her paper on niche conservatism with John J. Wiens is also highly cited. They focused on how species' retention of ancestral traits may limit geographic range expansion. In many of her papers, she has sought to unite ecology and evolutionary biology to derive a better understanding of the processes driving species diversity patterns. In particular, she and Paul Fine laid out a framework for interpreting community assembly processes from a phylogenetic approach to quantifying beta diversity.
Leslie Jane Rissler is an American biologist best known for her work on amphibian and reptile biogeography, evolutionary ecology, systematics, and conservation, and for her strong advocacy of improving the public’s understanding and appreciation of evolution. She is currently Program Officer in the Evolutionary Processes Cluster of the Division of Environmental Biology and Directorate of Biological Sciences at the National Science Foundation.
Nancy Huntly is an American ecologist based at Utah State University, where she is a Professor in the Department of Biology and director of the USU Ecology Center. Her research has been on biodiversity, herbivory, and long-term human ecology. She started her position at USU in 2011, after serving as a Program Officer in the Division of Environmental Biology at the National Science Foundation. Prior to that she was a faculty member in the Department of Biological Sciences at Idaho State University (Pocatello).
Allison K. Shaw is an American ecologist and professor at the University of Minnesota. She studies the factors that drive the movements of organisms.
Susan Patricia Harrison is a professor of ecology at the University of California, Davis who works on the dynamics of natural populations and ecological diversity. She is a fellow of the Ecological Society of America and the California Academy of Sciences. She has previously served as vice president of the American Society of Naturalists. She was elected to the National Academy of Sciences in 2018.
Mercedes Pascual is an Uruguayan theoretical ecologist, and a Professor in the Department of Ecology and Evolution at the University of Chicago, where she leads the Laboratory for Modeling and Theory in Ecology and Epidemiology (MATE). She was previously the Rosemary Grant Collegiate Professor at the University of Michigan and a Howard Hughes Medical Institute Investigator.
Jeannine Cavender-Bares is Professor of Organismic and Evolutionary Biology at Harvard University and Director of the Harvard University Herbaria. She is also adjunct professor in the Department of Ecology, Evolution & Behavior at the University of Minnesota, where she served on the faculty for over two decades. Her research integrates evolutionary biology, ecology, and physiology by studying the functional traits of plants, with a particular focus on oaks.
Stephanie M. Carlson is the A.S. Leopold Chair in Wildlife Biology at the University of California Berkeley. Her research considers fish ecology, freshwater ecology, and evolutionary ecology.
James A. Drake is an American ecologist.
Nancy Collins Johnson is an American earth scientist who is the Regents’ Professor and Director of the School of Earth Sciences & Environmental Sustainability at Northern Arizona University. Her work considers soil microbial ecology and the study of mycorrhizal fungi. She was elected a Fellow of the American Association for the Advancement of Science in 2020.
Tadashi Fukami is an associate Professor of Biology and community ecologist at Stanford University. He is currently the head of Fukami Lab which is a community ecology research group that focuses on "historical contingency in the assembly of ecological communities." Fukami is an elected Fellow of the Ecological Society of America.
Jessica Gurevitch is a plant ecologist known for meta-analysis in the fields of ecology and evolution.
Jennifer Dunne is an American ecologist whose research focuses on the network structure of food webs. One of 14 scientists who led critical advances in food web research over the last century, according to the journal Food Webs, Dunne uses ecological network research to compare the varying ways humans interact with other species through space and time, providing a quantitative perspective on sustainability of socio-ecological systems.
