Nikolaus Beck
- Published in print:
- 2008
- Published Online:
- September 2008
- ISBN:
- 9780199231423
- eISBN:
- 9780191710865
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199231423.003.0010
- Subject:
- Business and Management, Political Economy
This chapter shows that organizational ecology is much more sociological and less biological than many critics of organizational ecology think. It argues that organizational ecology and its theory of ...
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This chapter shows that organizational ecology is much more sociological and less biological than many critics of organizational ecology think. It argues that organizational ecology and its theory of competition rests heavily on the seminal work of Emile Durkheim on the division of labour, and on the thoughts of Amos Hawley on human ecology. It suggests that the expressions used by the agents of organizational ecology are ‘Darwinian’ but that the theoretical argumentation is ‘Durkheimian’. The chapter highlights the theoretical foundations of organizational ecology and emphasizes that competition — and not the biological aspects of evolution — forms the core of the organizational ecology theory. The most the most important sub-concepts of organizational ecology that deal with competition and market formation are also discussed: density dependence and resource partitioning. The first concept deals with the impact of the number of competitors on the survival and founding chances of organizations. The latter is concerned with the influence of market concentration on the vital rates of specialist and generalist organizations.Less
This chapter shows that organizational ecology is much more sociological and less biological than many critics of organizational ecology think. It argues that organizational ecology and its theory of competition rests heavily on the seminal work of Emile Durkheim on the division of labour, and on the thoughts of Amos Hawley on human ecology. It suggests that the expressions used by the agents of organizational ecology are ‘Darwinian’ but that the theoretical argumentation is ‘Durkheimian’. The chapter highlights the theoretical foundations of organizational ecology and emphasizes that competition — and not the biological aspects of evolution — forms the core of the organizational ecology theory. The most the most important sub-concepts of organizational ecology that deal with competition and market formation are also discussed: density dependence and resource partitioning. The first concept deals with the impact of the number of competitors on the survival and founding chances of organizations. The latter is concerned with the influence of market concentration on the vital rates of specialist and generalist organizations.
Franck Courchamp, Ludek Berec, and Joanna Gascoigne
- Published in print:
- 2008
- Published Online:
- May 2008
- ISBN:
- 9780198570301
- eISBN:
- 9780191717642
- Item type:
- book
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198570301.001.0001
- Subject:
- Biology, Biodiversity / Conservation Biology
Allee effects are broadly defined as a decline in individual fitness at low population size or density, that can result in critical population thresholds below which populations crash to extinction. ...
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Allee effects are broadly defined as a decline in individual fitness at low population size or density, that can result in critical population thresholds below which populations crash to extinction. As such, they are very relevant to many conservation programmes, where scientists and managers are often working with populations that have been reduced to low densities or small numbers. There are a variety of mechanisms that can create Allee effects, including mating systems, predation, environmental modification, and social interactions among others. The abrupt and unpredicted collapses of many exploited populations is just one illustration of the need to bring Allee effects to the forefront of conservation and management strategies. This book provides an overview of the topic, collating and integrating a widely dispersed literature from various fields: marine and terrestrial, plant and animal, theoretical and empirical, academic and applied. Less
Allee effects are broadly defined as a decline in individual fitness at low population size or density, that can result in critical population thresholds below which populations crash to extinction. As such, they are very relevant to many conservation programmes, where scientists and managers are often working with populations that have been reduced to low densities or small numbers. There are a variety of mechanisms that can create Allee effects, including mating systems, predation, environmental modification, and social interactions among others. The abrupt and unpredicted collapses of many exploited populations is just one illustration of the need to bring Allee effects to the forefront of conservation and management strategies. This book provides an overview of the topic, collating and integrating a widely dispersed literature from various fields: marine and terrestrial, plant and animal, theoretical and empirical, academic and applied.
Franck Courchamp, Luděk Berec, and Joanna Gascoigne
- Published in print:
- 2008
- Published Online:
- May 2008
- ISBN:
- 9780198570301
- eISBN:
- 9780191717642
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198570301.003.0002
- Subject:
- Biology, Biodiversity / Conservation Biology
This chapter describes the mechanisms by which an Allee effect can arise. For each mechanism, the chapter discusses how it works in theory, and then presents current evidence for, and examples of, ...
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This chapter describes the mechanisms by which an Allee effect can arise. For each mechanism, the chapter discusses how it works in theory, and then presents current evidence for, and examples of, the mechanisms in practice. It begins with reproductive mechanisms, including fertilization efficiency in broadcast spawners, pollen limitation, mate finding, sperm limitation, reproductive facilitation by conspecifics, and female choice. It then moves on to mechanisms related to survival: environmental conditioning and particularly predation, both via the dilution effect and via group ‘behaviour’, such as flocking, coloniality, and group vigilence. Finally, the chapter discusses Allee effects in social and cooperative species, where group size is important for both reproduction and survival.Less
This chapter describes the mechanisms by which an Allee effect can arise. For each mechanism, the chapter discusses how it works in theory, and then presents current evidence for, and examples of, the mechanisms in practice. It begins with reproductive mechanisms, including fertilization efficiency in broadcast spawners, pollen limitation, mate finding, sperm limitation, reproductive facilitation by conspecifics, and female choice. It then moves on to mechanisms related to survival: environmental conditioning and particularly predation, both via the dilution effect and via group ‘behaviour’, such as flocking, coloniality, and group vigilence. Finally, the chapter discusses Allee effects in social and cooperative species, where group size is important for both reproduction and survival.
Russell Lande, Steinar Engen, and Bernt-Erik SÆther
- Published in print:
- 2003
- Published Online:
- April 2010
- ISBN:
- 9780198525257
- eISBN:
- 9780191584930
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198525257.003.0003
- Subject:
- Biology, Ecology
The total density dependence in a life history is defined as the negative elasticity of population growth rate per generation with respect to population density. This chapter analyzes a ...
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The total density dependence in a life history is defined as the negative elasticity of population growth rate per generation with respect to population density. This chapter analyzes a stage-structured life history model with age at maturity α, and adult annual mortality and reproductive rates independent of age, with all density dependence exerted by the adult age class on all the vital rates. For small or moderate fluctuations in adult population size around an equilibrium or average size, a linear autoregressive equation is derived with time delays from 1 to α years. This demonstrates that a nonzero autoregression coefficient at a given time delay does not generally measure delayed density dependence, but also can be produced by intrinsic delays in the life history. The total density dependence in the life history can be estimated using the sum of the autoregression coefficients. Applying this theory to time series of terrestrial vertebrate populations reveals that, despite evidence for strong density dependence in some components of the life history, the expected dynamics of adult population size are undercompensated, γ less than 1. Thus, near equilibrium a proportional increase in adult population density is expected to produce a smaller proportional decrease in λ. Inspection of model autocorrelation functions and power spectra calculated by fitting population time series to the stage-structured life history shows that the expected dynamics are usually smoothly damped rather than cyclic or chaotic. Long autocorrelation and a red-shifted power spectrum are produced by a combination of weak density dependence and long generation times.Less
The total density dependence in a life history is defined as the negative elasticity of population growth rate per generation with respect to population density. This chapter analyzes a stage-structured life history model with age at maturity α, and adult annual mortality and reproductive rates independent of age, with all density dependence exerted by the adult age class on all the vital rates. For small or moderate fluctuations in adult population size around an equilibrium or average size, a linear autoregressive equation is derived with time delays from 1 to α years. This demonstrates that a nonzero autoregression coefficient at a given time delay does not generally measure delayed density dependence, but also can be produced by intrinsic delays in the life history. The total density dependence in the life history can be estimated using the sum of the autoregression coefficients. Applying this theory to time series of terrestrial vertebrate populations reveals that, despite evidence for strong density dependence in some components of the life history, the expected dynamics of adult population size are undercompensated, γ less than 1. Thus, near equilibrium a proportional increase in adult population density is expected to produce a smaller proportional decrease in λ. Inspection of model autocorrelation functions and power spectra calculated by fitting population time series to the stage-structured life history shows that the expected dynamics are usually smoothly damped rather than cyclic or chaotic. Long autocorrelation and a red-shifted power spectrum are produced by a combination of weak density dependence and long generation times.
David M. Wilkinson
- Published in print:
- 2006
- Published Online:
- September 2007
- ISBN:
- 9780198568469
- eISBN:
- 9780191717611
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198568469.003.0003
- Subject:
- Biology, Ecology
The problems faced by a hypothetical planet with only one species strongly suggest that any functioning ecological system must have organisms from at least two major ecological guilds: autotrophs and ...
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The problems faced by a hypothetical planet with only one species strongly suggest that any functioning ecological system must have organisms from at least two major ecological guilds: autotrophs and decomposers. While conventional predators do not seem to be crucial to planetary ecologies it is likely that parasites will quickly evolve, and through density dependent processes help to regulate population sizes. Density dependence may be crucial in preventing the runaway population growth of a species, leading to it monopolizing a planet's ecology. While density independent processes (be they a cold winter on a local scale, or the impact of a large meteorite at the planetary scale) can greatly affect abundance, they cannot provide regulation; this requires the ‘thermostat’ like behaviour of density dependence. As such, both multiple guilds and the presence of parasites are likely to have positive Gaian effects in most biospheres.Less
The problems faced by a hypothetical planet with only one species strongly suggest that any functioning ecological system must have organisms from at least two major ecological guilds: autotrophs and decomposers. While conventional predators do not seem to be crucial to planetary ecologies it is likely that parasites will quickly evolve, and through density dependent processes help to regulate population sizes. Density dependence may be crucial in preventing the runaway population growth of a species, leading to it monopolizing a planet's ecology. While density independent processes (be they a cold winter on a local scale, or the impact of a large meteorite at the planetary scale) can greatly affect abundance, they cannot provide regulation; this requires the ‘thermostat’ like behaviour of density dependence. As such, both multiple guilds and the presence of parasites are likely to have positive Gaian effects in most biospheres.
Frederic H. Wagner
- Published in print:
- 2006
- Published Online:
- September 2007
- ISBN:
- 9780195148213
- eISBN:
- 9780199790449
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780195148213.003.0002
- Subject:
- Biology, Ecology
Winter elk numbers on the northern range have been counted through most of its history, with ground counts up to 1956 (except 1935) and aerial counts up to the present. Several sightability bias ...
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Winter elk numbers on the northern range have been counted through most of its history, with ground counts up to 1956 (except 1935) and aerial counts up to the present. Several sightability bias tests have indicated that the censuses count approximately 70-75% of the herd. Regression of annual, instantaneous rates of change (r) between censuses of years t and t+1 on censuses of years t produces an inverse correlation with r reaching zero (equilibrium) at 16,800 (22,000-25,000 corrected for the sightability bias), and indicating density dependence. Below 16,800, the herd increased or held its numbers when hunting kills outside the park and park removals fell below 15-20%, but declined when removals exceeded this magnitude. While evidence of equilibration supports one tenet of the population aspect of the natural-regulation hypothesis, the 6x increase from a census of 3,172 in 1968 to 18,913 in 1988 (‘eruption’) falsifies two of the population tenets of the hypothesis.Less
Winter elk numbers on the northern range have been counted through most of its history, with ground counts up to 1956 (except 1935) and aerial counts up to the present. Several sightability bias tests have indicated that the censuses count approximately 70-75% of the herd. Regression of annual, instantaneous rates of change (r) between censuses of years t and t+1 on censuses of years t produces an inverse correlation with r reaching zero (equilibrium) at 16,800 (22,000-25,000 corrected for the sightability bias), and indicating density dependence. Below 16,800, the herd increased or held its numbers when hunting kills outside the park and park removals fell below 15-20%, but declined when removals exceeded this magnitude. While evidence of equilibration supports one tenet of the population aspect of the natural-regulation hypothesis, the 6x increase from a census of 3,172 in 1968 to 18,913 in 1988 (‘eruption’) falsifies two of the population tenets of the hypothesis.
Lev Ginzburg and Mark Colyvan
- Published in print:
- 2003
- Published Online:
- September 2007
- ISBN:
- 9780195168167
- eISBN:
- 9780199790159
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780195168167.003.0006
- Subject:
- Biology, Ecology
The term “inertia” was first used in population ecology in relation to the property of overshooting equilibria due to any one of a variety of causes. This chapter tries to flesh out the details of a ...
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The term “inertia” was first used in population ecology in relation to the property of overshooting equilibria due to any one of a variety of causes. This chapter tries to flesh out the details of a general account of inertia in population growth that can accommodate a number of possible mechanisms. To motivate this discussion, the chapter considers a couple of difficulties for the maternal effect. Both difficulties concern the inadequacy of existing data and require a little technical detail.Less
The term “inertia” was first used in population ecology in relation to the property of overshooting equilibria due to any one of a variety of causes. This chapter tries to flesh out the details of a general account of inertia in population growth that can accommodate a number of possible mechanisms. To motivate this discussion, the chapter considers a couple of difficulties for the maternal effect. Both difficulties concern the inadequacy of existing data and require a little technical detail.
Mark A. McPeek
- Published in print:
- 2008
- Published Online:
- September 2008
- ISBN:
- 9780199230693
- eISBN:
- 9780191710889
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199230693.003.0005
- Subject:
- Biology, Ecology, Animal Biology
This chapter reviews the ecological processes that define and limit the distributions and abundances of many odonate species across ecological environments. Distributions of species among standing ...
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This chapter reviews the ecological processes that define and limit the distributions and abundances of many odonate species across ecological environments. Distributions of species among standing bodies of water seem to be limited mainly by the distributions of their predators in the larval stage (e.g., larger dragonflies and fish). Although species also show restricted distributions among flowing water habitats, much less is known about the ecological processes that constrain their distributions. Many different types of species interactions (e.g., resource abundances, competitors, predators, parasites) contribute to the limitation of local abundances. Directions for potential future research are suggested.Less
This chapter reviews the ecological processes that define and limit the distributions and abundances of many odonate species across ecological environments. Distributions of species among standing bodies of water seem to be limited mainly by the distributions of their predators in the larval stage (e.g., larger dragonflies and fish). Although species also show restricted distributions among flowing water habitats, much less is known about the ecological processes that constrain their distributions. Many different types of species interactions (e.g., resource abundances, competitors, predators, parasites) contribute to the limitation of local abundances. Directions for potential future research are suggested.
J. Nathaniel Holland
- Published in print:
- 2015
- Published Online:
- September 2015
- ISBN:
- 9780199675654
- eISBN:
- 9780191809422
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199675654.003.0008
- Subject:
- Biology, Ecology, Evolutionary Biology / Genetics
Historically, studies of the population ecology of mutualism have been largely divorced from the key principles (e.g., density dependence, functional responses, consumer–resource theory) that have ...
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Historically, studies of the population ecology of mutualism have been largely divorced from the key principles (e.g., density dependence, functional responses, consumer–resource theory) that have shaped our understanding of the dynamics of predation and competition. The population ecology of mutualism has been slow to mature, largely due to unrealistic Lotka–Volterra theory. This chapter summarizes shortcomings of such historical models that stifled theory for decades, reviews the new generation of consumer–resource theory for the population dynamics of mutualism, synthesizes empirical studies of the density dependence of mutualism, and proposes future research directions. Contemporary advances in theory are emphasized, including mechanisms for the density dependence of mutualism for which research at the interface of theory and empiricism will be critical to future progress. The chapter builds a foundation for future theoretical and empirical work to enhance our understanding of the short-term transient dynamics and long-term stability properties of mutualistic interactions.Less
Historically, studies of the population ecology of mutualism have been largely divorced from the key principles (e.g., density dependence, functional responses, consumer–resource theory) that have shaped our understanding of the dynamics of predation and competition. The population ecology of mutualism has been slow to mature, largely due to unrealistic Lotka–Volterra theory. This chapter summarizes shortcomings of such historical models that stifled theory for decades, reviews the new generation of consumer–resource theory for the population dynamics of mutualism, synthesizes empirical studies of the density dependence of mutualism, and proposes future research directions. Contemporary advances in theory are emphasized, including mechanisms for the density dependence of mutualism for which research at the interface of theory and empiricism will be critical to future progress. The chapter builds a foundation for future theoretical and empirical work to enhance our understanding of the short-term transient dynamics and long-term stability properties of mutualistic interactions.
Cang Hui and David M. Richardson
- Published in print:
- 2017
- Published Online:
- March 2017
- ISBN:
- 9780198745334
- eISBN:
- 9780191807046
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198745334.003.0005
- Subject:
- Biology, Ecology, Biomathematics / Statistics and Data Analysis / Complexity Studies
The non-equilibrium dynamics of biological invasions has revived the debate on the balance of nature and mechanisms for population regulation. Invasive species in novel environments, whether ...
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The non-equilibrium dynamics of biological invasions has revived the debate on the balance of nature and mechanisms for population regulation. Invasive species in novel environments, whether experiencing the quasi-equilibrium of halted expansion during the lag phase or undergoing fast expansion to fulfil the opportunity niche, face a multitude of stabilizing and destabilizing forces that affect their population dynamics—from positive (Allee effects) and negative density dependence to rapidly shifting niches during invasion; these have major effects on population variability and spatial dynamics. The temporal and spatial dynamics are also intertwined, which means that the spatial structures of species distributions are potentially indicative of the invasiveness and population trends of target species. Time-series analysis for depicting the temporal population dynamics can be extended to capture the spatial synchrony dynamics of multiple local populations. Spatial autoregressive models further advance species distribution models to unveil the drivers of non-equilibrium dynamics of invasive species.Less
The non-equilibrium dynamics of biological invasions has revived the debate on the balance of nature and mechanisms for population regulation. Invasive species in novel environments, whether experiencing the quasi-equilibrium of halted expansion during the lag phase or undergoing fast expansion to fulfil the opportunity niche, face a multitude of stabilizing and destabilizing forces that affect their population dynamics—from positive (Allee effects) and negative density dependence to rapidly shifting niches during invasion; these have major effects on population variability and spatial dynamics. The temporal and spatial dynamics are also intertwined, which means that the spatial structures of species distributions are potentially indicative of the invasiveness and population trends of target species. Time-series analysis for depicting the temporal population dynamics can be extended to capture the spatial synchrony dynamics of multiple local populations. Spatial autoregressive models further advance species distribution models to unveil the drivers of non-equilibrium dynamics of invasive species.
Frederic H. Wagner
- Published in print:
- 2006
- Published Online:
- September 2007
- ISBN:
- 9780195148213
- eISBN:
- 9780199790449
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780195148213.003.0009
- Subject:
- Biology, Ecology
Nutritional research on northern-range elk and park-wide bison shows catabolic decline and mortality increase through winters, and as functions of population size and winter severity, collectively ...
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Nutritional research on northern-range elk and park-wide bison shows catabolic decline and mortality increase through winters, and as functions of population size and winter severity, collectively indicating usurpation of the range resource and intraspecific competition. Bighorn sheep numbers declined from the 1920s until about the 1960s, increased during and immediately after the elk population low, and then declined again in the 1980s and 1990s when they occurred at low population viability. Contrary to one hypothesis, the bison population increased steadily from the 1960s, except for slight population reductions in the 1980s and 1990s, until it reached ~3,000 when animals began leaving the park. Mule deer declined from the early 1900s to 1958-1970, and increased substantially by the 1980s and 1990s when they began wintering outside the park. Pronghorns, numbering in the thousands in early park years, now exist at low population viability. With speculative estimates, elk numbers and biomass increased 3.2x between park establishment and the 1990s; the other four species together declined 67% in numbers and 40% in biomass.Less
Nutritional research on northern-range elk and park-wide bison shows catabolic decline and mortality increase through winters, and as functions of population size and winter severity, collectively indicating usurpation of the range resource and intraspecific competition. Bighorn sheep numbers declined from the 1920s until about the 1960s, increased during and immediately after the elk population low, and then declined again in the 1980s and 1990s when they occurred at low population viability. Contrary to one hypothesis, the bison population increased steadily from the 1960s, except for slight population reductions in the 1980s and 1990s, until it reached ~3,000 when animals began leaving the park. Mule deer declined from the early 1900s to 1958-1970, and increased substantially by the 1980s and 1990s when they began wintering outside the park. Pronghorns, numbering in the thousands in early park years, now exist at low population viability. With speculative estimates, elk numbers and biomass increased 3.2x between park establishment and the 1990s; the other four species together declined 67% in numbers and 40% in biomass.
Douglas W. Morris and Per Lundberg
- Published in print:
- 2011
- Published Online:
- December 2013
- ISBN:
- 9780198568797
- eISBN:
- 9780191774690
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198568797.003.0006
- Subject:
- Biology, Evolutionary Biology / Genetics
Although we must understand the mechanical nuts and bolts of inheritance, evolution occurs through changes in the population frequencies of traits, trait values, and genes in time and space, values ...
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Although we must understand the mechanical nuts and bolts of inheritance, evolution occurs through changes in the population frequencies of traits, trait values, and genes in time and space, values that depend at least as much on the dynamics of populations as on the mechanics of inheritance. This chapter demonstrates the crucial roles of ecology in evolutionary change. There are two major types of dynamics that are essential to model evolution. The chapter develops the principles of strategy dynamics to examine the processes responsible for the success and failure of some traits, and trait values, over others. Different traits and their values represent competing strategies to be tested by adaptive evolution. The success of each strategy depends on the spatial and temporal dynamics of populations, and their respective influences on those dynamics. The chapter merges strategy and population dynamics to evaluate the evolutionary stability of competing strategies.Less
Although we must understand the mechanical nuts and bolts of inheritance, evolution occurs through changes in the population frequencies of traits, trait values, and genes in time and space, values that depend at least as much on the dynamics of populations as on the mechanics of inheritance. This chapter demonstrates the crucial roles of ecology in evolutionary change. There are two major types of dynamics that are essential to model evolution. The chapter develops the principles of strategy dynamics to examine the processes responsible for the success and failure of some traits, and trait values, over others. Different traits and their values represent competing strategies to be tested by adaptive evolution. The success of each strategy depends on the spatial and temporal dynamics of populations, and their respective influences on those dynamics. The chapter merges strategy and population dynamics to evaluate the evolutionary stability of competing strategies.
Jaboury Ghazoul
- Published in print:
- 2016
- Published Online:
- August 2016
- ISBN:
- 9780199639656
- eISBN:
- 9780191827167
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199639656.003.0009
- Subject:
- Biology, Plant Sciences and Forestry, Biodiversity / Conservation Biology
Population dynamics of dipterocarps is determined not only by their reproduction, but also by the growth and survival of the juveniles. This itself often depends on rates of tree mortality and gap ...
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Population dynamics of dipterocarps is determined not only by their reproduction, but also by the growth and survival of the juveniles. This itself often depends on rates of tree mortality and gap formation events. The natural disturbance regime is an important agent in creating opportunities for growth and recruitment into the canopy. There are many forms of natural disturbances, including drought, fire, windthrow, and landslides. The importance of these disturbances varies across the dipterocarp range, and with respect to local topography and climate. The variety of disturbances create different sizes and frequencies of canopy gap formation, which provide reproductive and growth opportunities that favour some species groups over others, often based on relative growth rates and light responses. This chapter addresses the dynamics of canopy trees, and that of seedlings, with a focus on density-dependence effects at local scales. The role of the natural disturbance regime in providing opportunities for recruitment and in shaping dipterocarp forest structure is also evaluated.Less
Population dynamics of dipterocarps is determined not only by their reproduction, but also by the growth and survival of the juveniles. This itself often depends on rates of tree mortality and gap formation events. The natural disturbance regime is an important agent in creating opportunities for growth and recruitment into the canopy. There are many forms of natural disturbances, including drought, fire, windthrow, and landslides. The importance of these disturbances varies across the dipterocarp range, and with respect to local topography and climate. The variety of disturbances create different sizes and frequencies of canopy gap formation, which provide reproductive and growth opportunities that favour some species groups over others, often based on relative growth rates and light responses. This chapter addresses the dynamics of canopy trees, and that of seedlings, with a focus on density-dependence effects at local scales. The role of the natural disturbance regime in providing opportunities for recruitment and in shaping dipterocarp forest structure is also evaluated.
Richard T. Corlett
- Published in print:
- 2014
- Published Online:
- November 2014
- ISBN:
- 9780199681341
- eISBN:
- 9780191789175
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199681341.003.0004
- Subject:
- Biology, Ecology
This chapter deals with the ecology of Tropical East Asia from a plant perspective. The life cycle of forest trees is covered in detail, including pollination, seed dispersal, seed predation, and the ...
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This chapter deals with the ecology of Tropical East Asia from a plant perspective. The life cycle of forest trees is covered in detail, including pollination, seed dispersal, seed predation, and the seedling, sapling, and adult stages. Other life forms, including lianas, ground herbs, epiphytes, and hemi-epiphytes, are considered in less detail. Recent advances in plant community ecology are discussed, including the mechanisms responsible for the maintenance of species diversity in tropical forests (growth–survival trade-offs, negative density dependence, Janzen–Connell effects, neutral theory), and the influence of functional traits and phylogeny on community assembly. Forest succession is discussed in a regional context.Less
This chapter deals with the ecology of Tropical East Asia from a plant perspective. The life cycle of forest trees is covered in detail, including pollination, seed dispersal, seed predation, and the seedling, sapling, and adult stages. Other life forms, including lianas, ground herbs, epiphytes, and hemi-epiphytes, are considered in less detail. Recent advances in plant community ecology are discussed, including the mechanisms responsible for the maintenance of species diversity in tropical forests (growth–survival trade-offs, negative density dependence, Janzen–Connell effects, neutral theory), and the influence of functional traits and phylogeny on community assembly. Forest succession is discussed in a regional context.
David W. Macdonald, Chris Newman, and Christina D. Buesching
- Published in print:
- 2015
- Published Online:
- September 2015
- ISBN:
- 9780198745501
- eISBN:
- 9780191821776
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198745501.003.0004
- Subject:
- Biology, Biodiversity / Conservation Biology, Ecology
Despite their emblematic status, assumed knowledge on the socio-ecology of badgers, even that based on older research, proves increasingly incongruous; providing an inadequate basis to decide ...
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Despite their emblematic status, assumed knowledge on the socio-ecology of badgers, even that based on older research, proves increasingly incongruous; providing an inadequate basis to decide management policy. Starting from 1987 at the Wytham Woods research site, the 9500 + captures of 1548 individuals, for which detailed data has been gathered, have afforded unique insights into badger society. This chapter demonstrates that they do not in fact live in discrete groups, but rather trespass into supposed neighbouring group ranges and visit other group setts. Here they mate, with almost 50% of cubs fathered by extra-group males, although with scant evidence of any offspring advantages. Only limited social interactions can be observed, typically on a purely reciprocal basis, and communication mediated primarily by scent secretion and olfaction. Population dynamics also prove intriguing, interacting strongly with weather conditions, in both absolute terms and with an adverse effect of unpredictable weather variability. Dry summers exacerbate the effect of endo-parasitic infections, leading to cub mortality; and while mild winters favour survival overall, greater ranging activity is associated with more traffic fatalities. Ultimately, the chapter exposes how it is the dispersion of key resources, and in particular earthworms, which best explains badger socio-spatial geometries. This intersects with agricultural practice and land management, where the mosaic of worm-rich fields, peppered with wooded copses, that typify the British countryside have created conditions where this otherwise more solitary mustelid thrives, and is consequently forced into high-density living. The result is an awkward compromise, where their socio-ecology lags their actual ecological circumstances.Less
Despite their emblematic status, assumed knowledge on the socio-ecology of badgers, even that based on older research, proves increasingly incongruous; providing an inadequate basis to decide management policy. Starting from 1987 at the Wytham Woods research site, the 9500 + captures of 1548 individuals, for which detailed data has been gathered, have afforded unique insights into badger society. This chapter demonstrates that they do not in fact live in discrete groups, but rather trespass into supposed neighbouring group ranges and visit other group setts. Here they mate, with almost 50% of cubs fathered by extra-group males, although with scant evidence of any offspring advantages. Only limited social interactions can be observed, typically on a purely reciprocal basis, and communication mediated primarily by scent secretion and olfaction. Population dynamics also prove intriguing, interacting strongly with weather conditions, in both absolute terms and with an adverse effect of unpredictable weather variability. Dry summers exacerbate the effect of endo-parasitic infections, leading to cub mortality; and while mild winters favour survival overall, greater ranging activity is associated with more traffic fatalities. Ultimately, the chapter exposes how it is the dispersion of key resources, and in particular earthworms, which best explains badger socio-spatial geometries. This intersects with agricultural practice and land management, where the mosaic of worm-rich fields, peppered with wooded copses, that typify the British countryside have created conditions where this otherwise more solitary mustelid thrives, and is consequently forced into high-density living. The result is an awkward compromise, where their socio-ecology lags their actual ecological circumstances.
James A. Estes, M. Tim Tinker, and Terrie M. Williams
- Published in print:
- 2017
- Published Online:
- January 2018
- ISBN:
- 9780198759805
- eISBN:
- 9780191820519
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780198759805.003.0023
- Subject:
- Biology, Animal Biology, Biodiversity / Conservation Biology
Sea otters are the only fully marine-living mustelid and the smallest extant marine mammal. They have the highest mass-specific metabolic rate of any marine mammal, which coupled with the lack of ...
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Sea otters are the only fully marine-living mustelid and the smallest extant marine mammal. They have the highest mass-specific metabolic rate of any marine mammal, which coupled with the lack of blubber for insulator and energy storage, relegates them to operating as an extreme income strategist, and appears to have led to a life history tactic in which pregnancy rate is fixed while reproductive success varies with the mother’s body condition at the time of birth, which triggers a decision immediately post-partum to care for or abandon her pup. When resources are limiting, sea otters assume highly individualized diets, which are inherited matrilineally. Sea otters exert strong limiting influences on their macroinvertebrate prey, leading to far reaching indirect effects on the structure and function of coastal marine ecosystems. This chapter reviews and synthesizes the interplay between sea otter energetics and life histories, diet and foraging behaviour, and ecosystem influences.Less
Sea otters are the only fully marine-living mustelid and the smallest extant marine mammal. They have the highest mass-specific metabolic rate of any marine mammal, which coupled with the lack of blubber for insulator and energy storage, relegates them to operating as an extreme income strategist, and appears to have led to a life history tactic in which pregnancy rate is fixed while reproductive success varies with the mother’s body condition at the time of birth, which triggers a decision immediately post-partum to care for or abandon her pup. When resources are limiting, sea otters assume highly individualized diets, which are inherited matrilineally. Sea otters exert strong limiting influences on their macroinvertebrate prey, leading to far reaching indirect effects on the structure and function of coastal marine ecosystems. This chapter reviews and synthesizes the interplay between sea otter energetics and life histories, diet and foraging behaviour, and ecosystem influences.
