scholarly journals Population Cycles Produced by Delayed Density Dependence in an Annual Plant

2006 ◽  
Vol 168 (3) ◽  
pp. 318-322 ◽  
Author(s):  
J. L. Gonzalez‐Andujar ◽  
C. Fernandez‐Quintanilla ◽  
L. Navarrete
Keyword(s):  
Density Dependence ◽  
Population Cycles ◽  
Annual Plant ◽  
Delayed Density Dependence

scholarly journals Population Cycles Produced by Delayed Density Dependence in an Annual Plant

2006 ◽  
Vol 168 (3) ◽  
pp. 318
Author(s):  
Gonzalez-Andujar ◽  
Fernandez-Quintanilla ◽  
Navarrete
Keyword(s):  
Density Dependence ◽  
Population Cycles ◽  
Annual Plant ◽  
Delayed Density Dependence

Population cycles caused by overcompensating density-dependence in an annual plant

Oecologia ◽  
1986 ◽  
Vol 71 (1) ◽  
pp. 156-158 ◽  
Author(s):  
E. Symonides ◽  
J. Silvertown ◽  
V. Andreasen
Keyword(s):  
Density Dependence ◽  
Population Cycles ◽  
Annual Plant

Geographic variation in population cycles of Canadian muskrats (Ondatra zibethicus)

2000 ◽  
Vol 78 (6) ◽  
pp. 1009-1016 ◽  
Author(s):  
John Erb ◽  
Nils Chr. Stenseth ◽  
Mark S Boyce
Keyword(s):  
Density Dependence ◽  
Trophic Interactions ◽  
Dynamic Properties ◽  
Population Cycles ◽  
Period Length ◽  
Ondatra Zibethicus ◽  
Delayed Density Dependence ◽  
Relative Contribution ◽  
Arctic Regions ◽  
Harvest Data

We investigated the dynamic properties of population cycles in Canadian muskrats (Ondatra zibethicus). Ninety-one historic time series of muskrat-harvest data obtained from the Hudson's Bay Company Archives were analyzed. Most series were 25 years in length (1925–1949) and were distributed primarily throughout five ecozones. For each series, we estimated period length and coefficients for a second-order autoregressive model. Estimated period length varied between 3 and 13 years, with 3- to 5-year periods located in Subarctic-Arctic ecozones. We hypothesize that the 4-year cycles are largely a result of predation by red fox (Vulpes vulpes), which exhibit 4-year cycles in Arctic regions. The remaining ecozones generally averaged 8–9 years in period length. However, the relative contributions of direct and delayed density dependence varied along a latitudinal gradient. We hypothesize that both social and trophic interactions are necessary to produce the observed dynamics, but that shifts in the nature of mink predation were responsible for the changes in the relative contribution of direct and delayed density dependence. Essentially, there is a tension between population-intrinsic and trophic interactions that may bound the length of the cycle.

scholarly journals Influence of delayed density and ultraviolet radiation on caterpillar granulovirus infection and mortality

2021 ◽  
Author(s):  
Adam Pepi ◽  
Vincent Pan ◽  
Richard Karban
Keyword(s):  
Ultraviolet Radiation ◽  
Viral Infection ◽  
Density Dependence ◽  
Infection Rate ◽  
Population Cycles ◽  
Viral Disease ◽  
Environmental Persistence ◽  
Density Dependent ◽  
Delayed Density Dependence ◽  
Occlusion Bodies

AbstractInfectious disease is an important potential driver of population cycles, but this must occur through delayed density-dependent infection and resulting fitness effects. Delayed density-dependent infection by baculoviruses can be caused by environmental persistence of viral occlusion bodies, which can be influenced by environmental factors. In particular, ultraviolet radiation is potentially important in reducing the environmental persistence of viruses by inactivating viral occlusion bodies.Delayed density-dependent viral infection has rarely been observed empirically at the population level although theory predicts that it is necessary for these pathogens to drive population cycles. Similarly, field studies have not examined the potential effects of ultraviolet radiation on viral infection rates in natural animal populations. We tested if viral infection is delayed density-dependent with the potential to drive cyclic dynamics and if ultraviolet radiation influences viral infection.We censused 18 moth populations across nearly 9° of latitude over two years and quantified the effects of direct and delayed density and ultraviolet radiation on granulovirus infection rate, infection severity, and survival to adulthood. Caterpillars were collected from each population in the field and reared in the laboratory.We found that infection rate, infection severity, and survival to adulthood exhibited delayed density-dependence. Ultraviolet radiation in the previous summer decreased infection severity, and increased survival probability of the virus. Structural equation modelling found that the effect of lagged density on moth survival was mediated through infection rate and infection severity, and was 2.5 fold stronger than the effect of ultraviolet radiation on survival through infection severity.Our findings provide clear evidence that delayed density dependence can arise through viral infection rate and severity in insects, which supports the role of viral disease as a potential mechanism, among others, that may drive insect population cycles. Furthermore, our findings support predictions that ultraviolet radiation can modify viral disease dynamics in insect populations, most likely through attenuating viral persistence in the environment.

Population dynamics of muskrats and mink: investigating contemporary patterns in a classic predator-prey system

2021 ◽  
Author(s):  
Adam A Ahlers ◽  
Timothy P Lyons ◽  
Edward J Heske
Keyword(s):  
United States ◽  
Population Dynamics ◽  
Density Dependence ◽  
American Mink ◽  
Population Cycles ◽  
The United States ◽  
Parameter Estimates ◽  
Predator Prey ◽  
Cycle Lengths ◽  
Southern Half

A well-studied predator-prey relationship between American mink (Neovison vison (Schreber, 1777)) and muskrats (Ondatra zibethicus (Linnaeus, 1766)) in Canada has advanced our understanding of population cycles including the influence of density dependence and lagged responses of predators to prey abundances. However, it is unclear if patterns observed in Canada extend across the southern half of their native range. We used data from the United States to create a 41-year time series of mink and muskrat harvest reports (1970-2011) for 36 states. After controlling for pelt-price effects, we used 2nd order autoregressive and Lomb-Scargle spectral density models to identify the presence and periodicity of muskrat population cycles. Additionally, we tested for evidence of delayed or direct density dependence and for predator-driven population dynamics. Our results suggest muskrat populations may cycle in parts of the United States; however, results varied by modeling approaches with Lomb-Scargle analyses providing more precise parameter estimates. Observed cycle lengths were longer than expected with weak amplitudes and we urge caution when interpreting these results. We did not detect evidence of a predator-prey relationship driven by a lagged numerical response of American mink. American mink and muskrat fur returns were largely correlated across the region suggesting extraneous factors likely synchronize both populations.

Population decline in semi-migratory caribou (Rangifer tarandus): intrinsic or extrinsic drivers?

2013 ◽  
Vol 91 (11) ◽  
pp. 820-828 ◽  
Author(s):  
Guillaume Bastille-Rousseau ◽  
James A. Schaefer ◽  
Shane P. Mahoney ◽  
Dennis L. Murray
Keyword(s):  
Density Dependence ◽  
Rangifer Tarandus ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Population Decline ◽  
Negative Relationship ◽  
Population Limitation ◽  
Continental Scale ◽  
Delayed Density Dependence ◽  
Winter Severity

Many populations of caribou (Rangifer tarandus (L., 1758)) across North America, including Newfoundland, are in a state of decline. This phenomenon may reflect continental-scale changes in either the extrinsic or the intrinsic factors affecting caribou abundance. We hypothesized that caribou decline reflected marked resource limitation and predicted that fluctuations should correspond to time-delayed density dependence associated with a decline in range quality and decadal trends in winter severity. By conducting time-series analysis using 12 populations and evaluating correlations between caribou abundance and trends in (i) vegetation available at calving (normalized difference vegetation index, NDVI), (ii) winter weather severity (index of North Atlantic Oscillation, NAO), and (iii) caribou morphometrics, we observed strong evidence of density dependence in population dynamics (i.e., a negative relationship between caribou population size and caribou morphometrics). Caribou population trajectories were time-delayed relative to winter severity, but not relative to calving-ground greenness. These island-wide correlations could not be traced to dispersal between herds, which appears rare at least for adult females. Our results suggest that trends in winter severity may synchronize broad-scale changes in caribou abundance that are driven by time-delayed density dependence, although it remains possible that calving-ground deterioration also may contribute to population limitation in Newfoundland. Our findings provide the basis for additional research into density dependence and caribou population decline.

A MODEL FOR ANNUAL PLANT DYNAMICS WITH SEED BANK AND DENSITY-DEPENDENT EFFECTS

1995 ◽  
Vol 03 (02) ◽  
pp. 531-541 ◽  
Author(s):  
MOHAMED KHALADI ◽  
MARC JARRY ◽  
MARTINE HOSSAERT-MCKEY
Keyword(s):  
Density Dependence ◽  
Seed Bank ◽  
Germination Rate ◽  
Linear Matrix ◽  
Annual Plant ◽  
Potential Fecundity ◽  
Change Of Variables ◽  
Seed Mortality ◽  
Complicated Model ◽  
Conditions Of Stability

A model is proposed for the population dynamics of an annual plant with a seed bank (i.e. in which a proportion of seeds remain dormant for at least one year). In this model, demographic parameters (dormancy and germination rate) of the seeds of the year are different from those of the seeds of the seed bank. First, a simple linear matrix model is deduced from the life cycle graph and a more complicated model is built by introducing density dependence effect. The obtained system, nonlinear with delay, can be simplified by a change of variables. A non-trivial fixed point of this system is obtained and the conditions of stability are studied. Under certain conditions (choice of exponential law for functional response of density dependence and absence of seed mortality before germination) we show that conditions of stability depend only on 3 parameters, the dormancy rate of the seeds of the year, dormancy rate of the seeds of the seed bank and the maximum potential fecundity of adults. Study of the behaviour of this model in the parameter space shows that the domain of demographic stability can be reduced if the dormancy rate of seeds of the year is low, even if the dormancy rate of seeds of the seed bank is high.

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