scholarly journals Density dependence and spatial heterogeneity limit the population growth rate of invasive pines at the landscape scale

Ecography ◽  
2021 ◽  
Author(s):  
Rowan Sprague ◽  
Philip E. Hulme ◽  
Elena Moltchanova ◽  
William Godsoe
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Spatial Heterogeneity ◽  
Density Dependence ◽  
Population Growth Rate ◽  
Landscape Scale

scholarly journals Density dependence in the camelid Vicugna vicugna: the recovery of a protected population in Chile

Oryx ◽  
2002 ◽  
Vol 36 (2) ◽  
pp. 118-125 ◽  
Author(s):  
C. Bonacic ◽  
D. W. Macdonald ◽  
J. Galaz ◽  
R. M. Sibly
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Density Dependence ◽  
Primary Productivity ◽  
Carrying Capacity ◽  
Population Growth Rate ◽  
Census Data ◽  
South American ◽  
Density Dependent ◽  
Vicugna Vicugna

The vicuña Vicugna vicugna is a wild South American camelid. Following over-exploitation, which brought the species to the brink of extinction in Chile in the 1960s, the population was protected. Since 1975 the population has been censused annually, generating one of the most extensive long-term census databases for any South American mammal. In this paper we use these data, and measures of environmental parameters, to describe the population growth trend of the species and to estimate carrying capacity. Our results indicate that the vicuña has been protected successfully in northern Chile. The census data reveal that, following protection, the population displayed logistic growth between 1975 and 1992. Population growth rate declined linearly with population size, which indicates a degree of density dependence. Density independent factors, such as rainfall, may also have been important. The principal density dependent effect observed was that birth rate declined in those family groups with the most breeding females. The carrying capacity of the study area was estimated from the census data and from models based on precipitation and local primary productivity. Using the census data, an estimation of carrying capacity as the asymptote of the fitted logistic curve suggested that the vicuña population should reach approximately 26,000 vicuñas, whereas estimation when the population growth rate was equated to zero gave a carrying capacity of c. 22,000. Coe's method based on local precipitation predicted 31,000 vicuña, whereas Lavenroth's method based on local primary productivity predicted 26,000 vicuña. In reality, the census data showed that the population peaked at 22,463 vicuñas in 1990. The results are discussed in relation to the need for better census techniques and the implications of density dependent effects for the management of the vicuña in Chile.

scholarly journals An evolutionary maximum principle for density-dependent population dynamics in a fluctuating environment

2009 ◽  
Vol 364 (1523) ◽  
pp. 1511-1518 ◽  
Author(s):  
Russell Lande ◽  
Steinar Engen ◽  
Bernt-Erik Sæther
Keyword(s):  
Growth Rate ◽  
Population Dynamics ◽  
Population Growth ◽  
Density Dependence ◽  
Stationary Distribution ◽  
Population Growth Rate ◽  
Long Term Evolution ◽  
Intrinsic Rate Of Increase ◽  
Term Evolution

The evolution of population dynamics in a stochastic environment is analysed under a general form of density-dependence with genetic variation in r and K , the intrinsic rate of increase and carrying capacity in the average environment, and in σ e 2 , the environmental variance of population growth rate. The continuous-time model assumes a large population size and a stationary distribution of environments with no autocorrelation. For a given population density, N , and genotype frequency, p , the expected selection gradient is always towards an increased population growth rate, and the expected fitness of a genotype is its Malthusian fitness in the average environment minus the covariance of its growth rate with that of the population. Long-term evolution maximizes the expected value of the density-dependence function, averaged over the stationary distribution of N . In the θ -logistic model, where density dependence of population growth is a function of N θ , long-term evolution maximizes E[ N θ ]=[1− σ e 2 /(2 r )] K θ . While σ e 2 is always selected to decrease, r and K are always selected to increase, implying a genetic trade-off among them. By contrast, given the other parameters, θ has an intermediate optimum between 1.781 and 2 corresponding to the limits of high or low stochasticity.

scholarly journals Density Dependence and Adult Survival Drive Dynamics in Two High Elevation Amphibian Populations

Diversity ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 478
Author(s):  
Amanda M. Kissel ◽  
Simone Tenan ◽  
Erin Muths
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Density Dependence ◽  
Population Growth Rate ◽  
Geometric Mean ◽  
High Elevation ◽  
Amphibian Conservation ◽  
Adult Survival ◽  
Extrinsic Factors ◽  
Open Population

Amphibian conservation has progressed from the identification of declines to mitigation, but efforts are hampered by the lack of nuanced information about the effects of environmental characteristics and stressors on mechanistic processes of population regulation. Challenges include a paucity of long-term data and scant information about the relative roles of extrinsic (e.g., weather) and intrinsic (e.g., density dependence) factors. We used a Bayesian formulation of an open population capture-recapture model and >30 years of data to examine intrinsic and extrinsic factors regulating two adult boreal chorus frogs (Pseudacris maculata) populations. We modelled population growth rate and apparent survival directly, assessed their temporal variability, and derived estimates of recruitment. Populations were relatively stable (geometric mean population growth rate >1) and regulated by negative density dependence (i.e., higher population sizes reduced population growth rate). In the smaller population, density dependence also acted on adult survival. In the larger population, higher population growth was associated with warmer autumns. Survival estimates ranged from 0.30–0.87, per-capita recruitment was <1 in most years, and mean seniority probability was >0.50, suggesting adult survival is more important to population growth than recruitment. Our analysis indicates density dependence is a primary driver of population dynamics for P. maculata adults.

scholarly journals Density dependence or climatic variation? Factors influencing survival, recruitment, and population growth rate of Virginia opossums

2014 ◽  
Vol 95 (2) ◽  
pp. 421-430 ◽  
Author(s):  
Elizabeth M. Troyer ◽  
Susan E. Cameron Devitt ◽  
Melvin E. Sunquist ◽  
Varun R. Goswami ◽  
Madan K. Oli
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Density Dependence ◽  
Population Growth Rate ◽  
Climatic Variation ◽  
Factors Influencing

scholarly journals The influence of context-dependent maternal effects on population dynamics: an experimental test

2009 ◽  
Vol 364 (1520) ◽  
pp. 1049-1058 ◽  
Author(s):  
S.J Plaistow ◽  
T.G Benton
Keyword(s):  
Growth Rate ◽  
Population Dynamics ◽  
Population Growth ◽  
Density Dependence ◽  
Maternal Effects ◽  
Maternal Effect ◽  
Population Growth Rate ◽  
High Density ◽  
Parental Effects ◽  
Low Density

Parental effects arise when either the maternal or paternal phenotype influences the phenotypes of subsequent generations. Simple analytical models assume maternal effects are a mechanism creating delayed density dependence. Such models predict that maternal effects can very easily lead to population cycles. Despite this, unambiguous maternal-effect mediated cycles have not been demonstrated in any system. Additionally, much evidence has arisen to invalidate the underlying assumption that there is a simple positive correlation between maternal performance and offspring performance. A key issue in understanding how maternal effects may affect population dynamics is determining how the expression of parental effects changes in different environments. In this study, we tested the hypothesis that maternal effects influence population dynamics in a context-dependent way. Populations of the soil mite, Sancassania berlesei , were set up at high density (500 eggs) or low density (50 eggs), with eggs that were either laid by young mothers or old mothers (a previously documented maternal effect in this system). The influence of maternal age on both population and egg and body-size dynamics was only observed in the populations initiated under low density rather than high density. This difference was attributable to the context-dependence of maternal effects at the individual level. In low-density (high food) conditions, maternal effects have an impact on offspring reproductive performance, creating an impact on the population growth rate. In high density (low food), maternal effects impact more on juvenile survival (not adult size or reproduction), creating a smaller impact on the population growth rate. This context dependence of effects at the population level means that, in fluctuating populations, maternal effects cause intermittent delayed density dependence that does not lead to persistent cycles.

scholarly journals Biological scaling in green algae: the role of cell size and geometry

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Helena Bestová ◽  
Jules Segrestin ◽  
Klaus von Schwartzenberg ◽  
Pavel Škaloud ◽  
Thomas Lenormand ◽  
...  
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Population Growth Rate ◽  
Internal Diffusion ◽  
Scaling Exponent ◽  
Power Scaling ◽  
Nutrient Distribution ◽  
Metabolic Scaling ◽  
Key Factor ◽  
Size And Morphology

AbstractThe Metabolic Scaling Theory (MST), hypothesizes limitations of resource-transport networks in organisms and predicts their optimization into fractal-like structures. As a result, the relationship between population growth rate and body size should follow a cross-species universal quarter-power scaling. However, the universality of metabolic scaling has been challenged, particularly across transitions from bacteria to protists to multicellulars. The population growth rate of unicellulars should be constrained by external diffusion, ruling nutrient uptake, and internal diffusion, operating nutrient distribution. Both constraints intensify with increasing size possibly leading to shifting in the scaling exponent. We focused on unicellular algae Micrasterias. Large size and fractal-like morphology make this species a transitional group between unicellular and multicellular organisms in the evolution of allometry. We tested MST predictions using measurements of growth rate, size, and morphology-related traits. We showed that growth scaling of Micrasterias follows MST predictions, reflecting constraints by internal diffusion transport. Cell fractality and density decrease led to a proportional increase in surface area with body mass relaxing external constraints. Complex allometric optimization enables to maintain quarter-power scaling of population growth rate even with a large unicellular plan. Overall, our findings support fractality as a key factor in the evolution of biological scaling.

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