scholarly journals Allee effects introduced by density dependent phenology.

2019 ◽  
Author(s):  
Timothy Pervenecki
Keyword(s):  
Allee Effects ◽  
Density Dependent

scholarly journals Modeling the effects of density dependent emigration, weak Allee effects, and matrix hostility on patch-level population persistence

2020 ◽  
Vol 17 (2) ◽  
pp. 1718-1742 ◽  
Author(s):  
James T. Cronin ◽  
◽  
Nalin Fonseka ◽  
Jerome Goddard II ◽  
Jackson Leonard ◽  
...  
Keyword(s):  
Population Persistence ◽  
Level Population ◽  
Allee Effects ◽  
Density Dependent ◽  
Effects Of Density

scholarly journals When higher carrying capacities lead to faster propagation

2018 ◽  
Author(s):  
Marjorie Haond ◽  
Thibaut Morel-Journel ◽  
Eric Lombaert ◽  
Elodie Vercken ◽  
Ludovic Mailleret ◽  
...  
Keyword(s):  
Carrying Capacity ◽  
Invasion Biology ◽  
Reaction Diffusion Equations ◽  
Positive Density ◽  
Allee Effects ◽  
Demographic Stochasticity ◽  
Positive Dependence ◽  
Density Dependent ◽  
Temporal Models ◽  
Density Dependent Dispersal

AbstractThis preprint has been reviewed and recommended by Peer Community In Ecology (https://dx.doi.org/10.24072/pci.ecology.100004). Finding general patterns in the expansion of natural populations is a major challenge in ecology and invasion biology. Classical spatio-temporal models predict that the carrying capacity (K) of the environment should have no influence on the speed (v) of an expanding population. We tested the generality of this statement with reaction-diffusion equations, stochastic individual-based models, and microcosms experiments with Trichogramma chilonis wasps. We investigated the dependence between K and v under different assumptions: null model (Fisher-KPP-like assumptions), strong Allee effects, and positive density-dependent dispersal. These approaches led to similar and complementary results. Strong Allee effects, positive density-dependent dispersal and demographic stochasticity in small populations lead to a positive dependence between K and v. A positive correlation between carrying capacity and propagation speed might be more frequent than previously expected, and be the rule when individuals at the edge of a population range are not able to fully drive the expansion.

scholarly journals Can't live with them, can't live without them? Balancing mating and competition in two-sex populations

2017 ◽  
Vol 284 (1865) ◽  
pp. 20171999 ◽  
Author(s):  
Aldo Compagnoni ◽  
Kenneth Steigman ◽  
Tom E. X. Miller
Keyword(s):  
Sex Ratio ◽  
Mating Success ◽  
Sex Ratios ◽  
Structured Populations ◽  
Allee Effects ◽  
Mate Finding ◽  
Frequency Dependent ◽  
Density Dependent ◽  
Positive Effects ◽  
Demographic Processes

Two-sex populations are usually studied through frequency-dependent models that describe how sex ratio affects mating, recruitment and population growth. However, in two-sex populations, mating and recruitment should also be affected by density and by its interactions with the sex ratio. Density may have positive effects on mating (Allee effects) but negative effects on other demographic processes. In this study, we quantified how positive and negative inter-sexual interactions balance in two-sex populations. Using a dioecious grass ( Poa arachnifera ), we established experimental field populations that varied in density and sex ratio. We then quantified mating success (seed fertilization) and non-mating demographic performance, and integrated these responses to project population-level recruitment. Female mating success was positively density-dependent, especially at female-biased sex ratios. Other demographic processes were negatively density-dependent and, in some cases, frequency-dependent. Integrating our experimental results showed that mate-finding Allee effects dominated other types of density-dependence, giving rise to recruitment that increased with increasing density and peaked at intermediate sex ratios, reflecting tension between seed initiation (greater with more females) and seed viability (greater with more males). Our results reveal, for the first time, the balance of positive and negative inter-sexual interactions in sex-structured populations. Models that account for both density- and sex ratio dependence, particularly in mating, may be necessary for understanding and predicting two-sex population dynamics.

Density‐dependent prey behaviours and mutable predator foraging modes induce Allee effects and over‐prediction of prey mortality rates

2020 ◽  
Vol 65 (10) ◽  
pp. 1752-1764
Author(s):  
Zachary A. Siders ◽  
Robert N. M. Ahrens ◽  
Micheal S. Allen ◽  
Carl J. Walters
Keyword(s):  
Mortality Rates ◽  
Allee Effects ◽  
Density Dependent ◽  
Foraging Modes ◽  
Predator Foraging

scholarly journals Pushed beyond the brink: Allee effects, environmental stochasticity, and extinction

2014 ◽  
Author(s):  
Gregory Roth ◽  
Sebastian Schreiber
Keyword(s):  
High Probability ◽  
Geometric Mean ◽  
Environmental Stochasticity ◽  
Initial Population ◽  
Positive Density ◽  
Allee Effects ◽  
Population Densities ◽  
Density Dependent ◽  
Environmental Fluctuations ◽  
Predation Rates

To understand the interplay between environmental stochasticity and Allee effects, we analyze persistence, asymptotic extinction, and conditional persistence for stochastic difference equations. Our analysis reveals that persistence requires that the geometric mean of fitness at low densities is greater than one. When this geometric mean is less than one, asymptotic extinction occurs with high probability for low initial population densities. Additionally, if the population only experiences positive density-dependent feedbacks, conditional persistence occurs provided the geometric mean of fitness at high population densities is greater than one. However, if the population experiences both positive and negative density-dependent feedbacks, conditional persistence only occurs if environmental fluctuations are sufficiently small. We illustrate counter-intuitively that environmental fluctuations can increase the probability of persistence when populations are initially at low densities, and can cause asymptotic extinction of populations experiencing intermediate predation rates despite conditional persistence occurring at higher predation rates.

scholarly journals Density‐dependent selection on mate search and evolution of Allee effects

2017 ◽  
Vol 87 (1) ◽  
pp. 24-35 ◽  
Author(s):  
Luděk Berec ◽  
Andrew M. Kramer ◽  
Veronika Bernhauerová ◽  
John M. Drake
Keyword(s):  
Allee Effects ◽  
Density Dependent ◽  
Mate Search ◽  
Density Dependent Selection

Urbanization impacts on production and recruitment of Fundulus heteroclitus in salt marsh creeks

2020 ◽  
Vol 645 ◽  
pp. 187-204
Author(s):  
PJ Rudershausen ◽  
JA Buckel
Keyword(s):  
Salt Marsh ◽  
Salt Marshes ◽  
Fundulus Heteroclitus ◽  
Multiple Factor Analysis ◽  
Southeastern Usa ◽  
Density Dependent ◽  
Dependent Relationship ◽  
Juvenile Abundance ◽  
The Relationship ◽  
Throw Trap

It is unclear how urbanization affects secondary biological production in estuaries in the southeastern USA. We estimated production of larval/juvenile Fundulus heteroclitus in salt marsh areas of North Carolina tidal creeks and tested for factors influencing production. F. heteroclitus were collected with a throw trap in salt marshes of 5 creeks subjected to a range of urbanization intensities. Multiple factor analysis (MFA) was used to reduce dimensionality of habitat and urbanization effects in the creeks and their watersheds. Production was then related to the first 2 dimensions of the MFA, month, and year. Lastly, we determined the relationship between creek-wide larval/juvenile production and abundance from spring and abundance of adults from autumn of the same year. Production in marsh (g m-2 d-1) varied between years and was negatively related to the MFA dimension that indexed salt marsh; higher rates of production were related to creeks with higher percentages of marsh. An asymptotic relationship was found between abundance of adults and creek-wide production of larvae/juveniles and an even stronger density-dependent relationship was found between abundance of adults and creek-wide larval/juvenile abundance. Results demonstrate (1) the ability of F. heteroclitus to maintain production within salt marsh in creeks with a lesser percentage of marsh as long as this habitat is not removed altogether and (2) a density-dependent link between age-0 production/abundance and subsequent adult recruitment. Given the relationship between production and marsh area, natural resource agencies should consider impacts of development on production when permitting construction in the southeastern USA.

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