Effect of resource competition on the long-term allocation of grooming by female baboons: evaluating Seyfarth's model

2003 ◽  
Vol 66 (5) ◽  
pp. 931-938 ◽  
Author(s):  
S.P. Henzi ◽  
L. Barrett ◽  
D. Gaynor ◽  
J. Greeff ◽  
T. Weingrill ◽  
...  
Keyword(s):  
Resource Competition ◽  
Seyfarth’S Model

scholarly journals Asymmetric competition causes multimodal size distributions in spatially structured populations

2016 ◽  
Vol 283 (1823) ◽  
pp. 20152404 ◽  
Author(s):  
Jorge Velázquez ◽  
Robert B. Allen ◽  
David A. Coomes ◽  
Markus P. Eichhorn
Keyword(s):  
Resource Competition ◽  
Structured Populations ◽  
Necessary Condition ◽  
Small Scale ◽  
Asymmetric Competition ◽  
Size Distributions ◽  
Long Term Study ◽  
Multimodal Distributions ◽  
Using Data

Plant sizes within populations often exhibit multimodal distributions, even when all individuals are the same age and have experienced identical conditions. To establish the causes of this, we created an individual-based model simulating the growth of trees in a spatially explicit framework, which was parametrized using data from a long-term study of forest stands in New Zealand. First, we demonstrate that asymmetric resource competition is a necessary condition for the formation of multimodal size distributions within cohorts. By contrast, the legacy of small-scale clustering during recruitment is transient and quickly overwhelmed by density-dependent mortality. Complex multi-layered size distributions are generated when established individuals are restricted in the spatial domain within which they can capture resources. The number of modes reveals the effective number of direct competitors, while the separation and spread of modes are influenced by distances among established individuals. Asymmetric competition within local neighbourhoods can therefore generate a range of complex size distributions within even-aged cohorts.

scholarly journals Growth, death, and resource competition in sessile organisms

2021 ◽  
Vol 118 (15) ◽  
pp. e2020424118
Author(s):  
Edward D. Lee ◽  
Christopher P. Kempes ◽  
Geoffrey B. West
Keyword(s):  
Evolutionary Dynamics ◽  
Resource Competition ◽  
Temporal Dynamics ◽  
Population Level ◽  
Individual Growth ◽  
Local Competition ◽  
Large Colony ◽  
Rates Of Growth ◽  
Sessile Organisms

Population-level scaling in ecological systems arises from individual growth and death with competitive constraints. We build on a minimal dynamical model of metabolic growth where the tension between individual growth and mortality determines population size distribution. We then separately include resource competition based on shared capture area. By varying rates of growth, death, and competitive attrition, we connect regular and random spatial patterns across sessile organisms from forests to ants, termites, and fairy circles. Then, we consider transient temporal dynamics in the context of asymmetric competition, such as canopy shading or large colony dominance, whose effects primarily weaken the smaller of two competitors. When such competition couples slow timescales of growth to fast competitive death, it generates population shocks and demographic oscillations similar to those observed in forest data. Our minimal quantitative theory unifies spatiotemporal patterns across sessile organisms through local competition mediated by the laws of metabolic growth, which in turn, are the result of long-term evolutionary dynamics.

scholarly journals Stochastic Modeling of Density-Dependent Diploid Populations and the Extinction Vortex

2014 ◽  
Vol 46 (2) ◽  
pp. 446-477 ◽  
Author(s):  
Camille Coron
Keyword(s):  
Resource Competition ◽  
Adaptive Dynamics ◽  
Three Dimensional ◽  
Death Process ◽  
Fixation Rate ◽  
One Dimensional ◽  
Rare Mutations ◽  
Recurrence Relationship ◽  
Extinction Vortex

We model and study the genetic evolution and conservation of a population of diploid hermaphroditic organisms, evolving continuously in time and subject to resource competition. In the absence of mutations, the population follows a three-type, nonlinear birth-and-death process, in which birth rates are designed to integrate Mendelian reproduction. We are interested in the long-term genetic behavior of the population (adaptive dynamics), and in particular we compute the fixation probability of a slightly nonneutral allele in the absence of mutations, which involves finding the unique subpolynomial solution of a nonlinear three-dimensional recurrence relationship. This equation is simplified to a one-dimensional relationship which is proved to admit exactly one bounded solution. Adding rare mutations and rescaling time, we study the successive mutation fixations in the population, which are given by the jumps of a limiting Markov process on the genotypes space. At this time scale, we prove that the fixation rate of deleterious mutations increases with the number of already fixed mutations, which creates a vicious circle called the extinction vortex.

scholarly journals Niche partitioning among dead wood-dependent beetles

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jakub Horák
Keyword(s):  
Dead Wood ◽  
Resource Competition ◽  
Niche Partitioning ◽  
Species Abundance ◽  
Landscape Scale ◽  
Habitat Requirements ◽  
Wood Material ◽  
Neutral Drift ◽  
Species Abundances

AbstractNiche partitioning among species with virtually the same requirements is a fundamental concept in ecology. Nevertheless, some authors suggest that niches have little involvement in structuring communities. This study was done in the Pardubice Region (Czech Republic) on saproxylic beetles with morphologically similar larvae and very specific requirements, which are related to their obligatory dependence on dead wood material: Cucujus cinnaberinus, Pyrochroa coccinea, and Schizotus pectinicornis. This work was performed on 232 dead wood pieces at the landscape scale over six years. Based on the factors studied, the relationships among these species indicated that their co-occurrence based on species presence and absence was low, which indicated niche partitioning. However, based on analyses of habitat requirements and species composition using observed species abundances, there was no strong evidence for niche partitioning at either studied habitat levels, the tree and the microhabitat. The most likely reasons for the lack of strong niche partitioning were that dead wood is a rich resource and co-occurrence of saproxylic community was not driven by resource competition. This might be consistent with the theory that biodiversity could be controlled by the neutral drift of species abundance. Nevertheless, niche partitioning could be ongoing, meaning that the expanding C. cinnaberinus may have an advantage over the pyrochroids and could dominate in the long term.

scholarly journals Population Viability and Resource Competition on North Brother Island: Conservation Implications for Tuatara (Sphenodon Punctatus) and Duvaucel's Gecko (Hoplodactylus Duvaucelii)

2021 ◽  
Author(s):  
◽  
Joanna Wilson
Keyword(s):  
Sex Ratio ◽  
Population Size ◽  
Body Condition ◽  
Resource Competition ◽  
Adult Population ◽  
Population Viability ◽  
Adult Survival ◽  
Intraspecific Interactions ◽  
Sphenodon Punctatus

<p>Population viability for small, isolated populations is determined by many factors, particularly demographic stochasticity. Coexistence of communities is promoted through resource partitioning, particularly if species share similar niche requirements. Demographic characteristics, long-term trends and patterns of partitioning were investigated for two reptile species: tuatara (Sphenodon punctatus) and Duvaucel's gecko (Hoplodactylus duvaucelii), using mark recapture techniques on North Brother Island, New Zealand. Capture time and location were recorded as well as snout-vent length, mass and sex of individuals. Adult population size, sex ratio, survival and recapture probability for both species were estimated. Intervention will be needed to prevent population collapse for tuatara, as the population is male-biased (3.24 males: 1 female), with sub-adults exhibiting a stronger bias (4.1 males: 1 female). The total population size is estimated at 390-437 adults, with high adult survival (95%). The Duvaucel's gecko population is stable enough to be harvested for translocation, as the population was estimated at 583-677 adults, with an even sex ratio. Adult survival was high (92%) and longevity is at least 43-50 years. Patterns in partitioning suggest tuatara are excluding Duvaucel's gecko as tuatara occupy vegetated areas and few animals were caught at the same time in the same place as a member of the other species (~10%). Long-term site fidelity appears to occur in both species as the majority of animals were captured previously within 10m (tuatara) or 15m (Duvaucel's gecko) of their 2008 location, and travelled less than 2m per year on average. Tuatara show an overall decline in body condition since 1957, which is more rapid in females, and may be related to intraspecific interactions and density-dependent effects. Gecko body condition is not declining, suggesting no negative effects at the population level are occurring as a result of competitive exclusion. This study indicates that characteristics that have implications for population viability have the capacity to differ, even for species with similar niche requirements occupying the same habitat, and supports the considerable value of long-term monitoring.</p>

Listening to Nature and Letting Data Be “Trump”

2016 ◽  
Author(s):  
David Tilman
Keyword(s):  
Field Experiments ◽  
Resource Competition ◽  
Associate Professor ◽  
Freshwater Algae ◽  
Rigorous Results ◽  
Cedar Creek ◽  
Grassland Ecosystems ◽  
Theoretical Predictions ◽  
Long Term Ecological Research

My long-term research, which has focused on major ecological mysteries and questions, has provided many unexpected insights into the processes, mechanisms, and feedbacks that determine the structure and functioning of the grassland ecosystems. Many of these insights have emerged from exploring these questions with a combination of well-replicated field experiments, long-term observations, and predictions of theory. A major source of research creativity has been my instinct to pay the deepest attention to any rigorous results that fall outside the realm of current paradigms, concepts, or theoretical predictions, including the predictions of my own theories. I refer to this as “listening to nature” and letting data be “trump.” It is when current ideas fail and “things fall apart” that new hypotheses are generated that are so crucial for the advancement of science. My teaching builds on this approach: trying to have each lecture explore a mystery or paradox, including those with which I am currently grappling, and challenging my students to propose solutions. Perhaps because they are not saturated with the current paradigms of ecology, students and members of the public frequently respond to ecological mysteries with great creativity. I believe that the amazing privilege of having public support for my research obliges me to communicate my findings of relevance to society through public talks, testimony to legislative committees, interviews with the media, and discussion with business leaders. In 1981, when we were writing the initial Cedar Creek Long-Term Ecological Research (LTER) proposal, I was a 32-year-old, 6-year-post-PhD associate professor at the University of Minnesota. I had spent most of my career doing mathematical theory and laboratory studies of resource competition between freshwater algae. I had started doing nutrient-addition field experiments in the Cedar Creek grasslands only 3 years earlier and had just finished writing a book on resource competition (Tilman 1982). Hutchinson’s (1961) “paradox of the plankton”—the search for the forces and processes that allowed so many competing species to coexist with each other, whether algae in lakes, herbaceous species in grasslands, or trees in tropical forests—was intriguing.

scholarly journals Population Viability and Resource Competition on North Brother Island: Conservation Implications for Tuatara (Sphenodon Punctatus) and Duvaucel's Gecko (Hoplodactylus Duvaucelii)

2021 ◽  
Author(s):  
◽  
Joanna Wilson
Keyword(s):  
Sex Ratio ◽  
Population Size ◽  
Body Condition ◽  
Resource Competition ◽  
Adult Population ◽  
Population Viability ◽  
Adult Survival ◽  
Intraspecific Interactions ◽  
Sphenodon Punctatus

<p>Population viability for small, isolated populations is determined by many factors, particularly demographic stochasticity. Coexistence of communities is promoted through resource partitioning, particularly if species share similar niche requirements. Demographic characteristics, long-term trends and patterns of partitioning were investigated for two reptile species: tuatara (Sphenodon punctatus) and Duvaucel's gecko (Hoplodactylus duvaucelii), using mark recapture techniques on North Brother Island, New Zealand. Capture time and location were recorded as well as snout-vent length, mass and sex of individuals. Adult population size, sex ratio, survival and recapture probability for both species were estimated. Intervention will be needed to prevent population collapse for tuatara, as the population is male-biased (3.24 males: 1 female), with sub-adults exhibiting a stronger bias (4.1 males: 1 female). The total population size is estimated at 390-437 adults, with high adult survival (95%). The Duvaucel's gecko population is stable enough to be harvested for translocation, as the population was estimated at 583-677 adults, with an even sex ratio. Adult survival was high (92%) and longevity is at least 43-50 years. Patterns in partitioning suggest tuatara are excluding Duvaucel's gecko as tuatara occupy vegetated areas and few animals were caught at the same time in the same place as a member of the other species (~10%). Long-term site fidelity appears to occur in both species as the majority of animals were captured previously within 10m (tuatara) or 15m (Duvaucel's gecko) of their 2008 location, and travelled less than 2m per year on average. Tuatara show an overall decline in body condition since 1957, which is more rapid in females, and may be related to intraspecific interactions and density-dependent effects. Gecko body condition is not declining, suggesting no negative effects at the population level are occurring as a result of competitive exclusion. This study indicates that characteristics that have implications for population viability have the capacity to differ, even for species with similar niche requirements occupying the same habitat, and supports the considerable value of long-term monitoring.</p>

Evaluation of a mechanistic approach to mixedwood modelling

2008 ◽  
Vol 84 (2) ◽  
pp. 181-193 ◽  
Author(s):  
B. Seely ◽  
C. Hawkins ◽  
J A Blanco ◽  
C. Welham ◽  
J P Kimmins
Keyword(s):  
Species Interactions ◽  
Resource Competition ◽  
Forest Type ◽  
Forest Growth ◽  
Nutrient Competition ◽  
Forest Types ◽  
Support Tool ◽  
Management Interventions ◽  
Forest Growth Model

Mixed conifer–broadleaf forests (mixedwoods), covering more than a third of the productive forest landbase in BC, are highly valuable both as sources of fibre and as areas rich in biodiversity. In recognition of the multiple benefits of this forest type, management paradigms have transitioned from a focus on promoting conifer plantations in mixedwood areas to the management of intimate mixtures. The exceptionally dynamic growth properties and species interactions in mixedwood forests present a challenge for projecting the growth and development of different types of mixedwoods and their response to different silviculture systems. Here we evaluate the ability of a mechanistic forest growth model (FORECAST) to project patterns of stand growth and dynamics in two mixedwood forest types subjected to different silvicultural treatments. Model output is compared against field measurements from long-term silviculture trials in the Sub Boreal Spruce (SBS)—18 years, and Interior Cedar Hemlock (ICH)—10 years, biogeoclimatic zones in British Columbia, Canada. FORECAST was able to reproduce patterns of growth response in both mixedwood forest types with reasonable accuracy. An analysis of the simulated relative impact of light and nutrient competition on growth dynamics and treatment response is provided. Results suggest that competition for both light and nutrients are important factors in the dynamics of these mixedwood forest types and that long-term response data and modelling are required to adequately assess the rotation-length effects of treatments on stand development. The analysis described herein provides a level of confidence for the use of the model as a decision-support tool in these ecosystem types, but more validation work should be conducted across a range of different mixedwood forest types and management interventions as long-term datasets become available. Key words: FORECAST, mixedwood management, model testing, process-based model, resource competition

scholarly journals Predicting the outcome of competition when fitness inequality is variable

2015 ◽  
Vol 2 (8) ◽  
pp. 150274 ◽  
Author(s):  
Michael T. Pedruski ◽  
Gregor F. Fussmann ◽  
Andrew Gonzalez
Keyword(s):  
Numerical Simulations ◽  
Resource Competition ◽  
Neutral Theory ◽  
Competitive Dynamics ◽  
Initial Population ◽  
Niche Theory ◽  
Demographic Stochasticity ◽  
Initial Population Size ◽  
Unexpected Outcomes

Traditional niche theory predicts that when species compete for one limiting resource in simple ecological settings the more fit competitor should exclude the less fit competitor. Since the advent of neutral theory ecologists have increasingly become interested both in how the magnitude of fitness inequality between competitors and stochasticity may affect this prediction. We used numerical simulations to investigate the outcome of two-species resource competition along gradients of fitness inequality (inequality in R *) and initial population size in the presence of demographic stochasticity. We found that the deterministic prediction of more fit competitors excluding less fit competitors was often unobserved when fitness inequalities were low or stochasticity was strong, and unexpected outcomes such as dominance by the less fit competitor, long-term co-persistence of both competitors or the extinction of both competitors could be common. By examining the interaction between fitness inequality and stochasticity our results mark the range of parameter space in which the predictions of niche theory break down most severely, and suggest that questions about whether competitive dynamics are driven by neutral or niche processes may be locally contingent.

scholarly journals Time-dependent fitness effects can drive bet-hedging populations extinct

2016 ◽  
Author(s):  
Eric Libby ◽  
William Ratcliff
Keyword(s):  
Resource Competition ◽  
Bet Hedging ◽  
Short Term ◽  
Time Intervals ◽  
Hedging Strategies ◽  
Diversification Strategies ◽  
Environmental Fluctuations ◽  
Long Time ◽  
Temporally Correlated

AbstractTo survive unpredictable environmental change, many organisms adopt bet-hedging strategies that trade short-term population growth for long-term fitness benefits. Because the benefits of bet-hedging may manifest over long time intervals, bet-hedging strategies may be out-competed by strategies maximizing short-term fitness. Here, we investigate the interplay between two drivers of selection, environmental fluctuations and competition for limited resources, on different bet-hedging strategies. We consider an environment with frequent disasters that switch between which phenotypes they affect in a temporally-correlated fashion. We determine how organisms that stochastically switch between phenotypes at different rates fare in both competition and survival. When disasters are correlated in time, the best strategy for competition is among the worst for survival. Since the time scales over which the two agents of selection act are significantly different, environmental fluctuations and resource competition act in opposition and lead populations to evolve diversification strategies that ultimately drive them extinct.

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