scholarly journals Jensen’s Inequality and the Impact of Short-Term Environmental Variability on Long-Term Population Growth Rates

PLoS ONE ◽  
2015 ◽  
Vol 10 (9) ◽  
pp. e0136072 ◽  
Author(s):  
Evan J. Pickett ◽  
David L. Thomson ◽  
Teng A. Li ◽  
Shuang Xing
Keyword(s):  
Population Growth ◽  
Growth Rates ◽  
Environmental Variability ◽  
Jensen’S Inequality ◽  
Jensen's Inequality ◽  
Short Term ◽  
Population Growth Rates ◽  
The Impact

An Evaluation of RNA–DNA Ratio as a Measure of Long-Term Growth in Fish Populations

1973 ◽  
Vol 30 (2) ◽  
pp. 195-199 ◽  
Author(s):  
Terry A. Haines
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Growth Rates ◽  
Population Growth Rate ◽  
Environmental Changes ◽  
Age Distribution ◽  
Smallmouth Bass ◽  
Fish Populations ◽  
Population Growth Rates

The value of RNA–DNA ratio as a measure of long-term growth of fish populations under semi-natural conditions and when subjected to environmental manipulations was determined. Populations of carp and smallmouth bass of known age distribution were established in artificial ponds maintained at two fertility levels. After 15 months, population growth rates (as percent increase in weight) and RNA–DNA ratios of muscle tissue from selected fish were measured. Each species exhibited a range of population growth rates. The relation between population growth rate and individual fish RNA–DNA ratio for each species was significant. When reproduction occurred, the relation was not significant unless young-of-the-year fish were excluded from population growth rate calculations. Age of fish was also found to have an important effect on RNA–DNA ratio, with the ratio being higher in younger fish.RNA–DNA ratio can be a reliable indicator of long-term population growth in fish when population age structure is known and recruitment is controlled. The method has potential for use in detecting response to environmental changes before growth rate changes become severe.

Using population dynamics modelling to evaluate potential success of restoration: a case study of a Hawaiian vine in a changing climate

2014 ◽  
Vol 42 (1) ◽  
pp. 20-30 ◽  
Author(s):  
TAMARA M. WONG ◽  
TAMARA TICKTIN
Keyword(s):  
Population Growth ◽  
Growth Rates ◽  
Key Management ◽  
Demographic Data ◽  
Population Decline ◽  
Management Strategies ◽  
Survival Rates ◽  
Population Modelling ◽  
Population Growth Rates

SUMMARYDemographic comparisons between wild and restored populations of at-risk plant species can reveal key management strategies for effective conservation, but few such studies exist. This paper evaluates the potential restoration success ofAlyxia stellata, a Hawaiian vine. Stage-structured matrix projection models that compared long-term and transient dynamics of wild versus restoredA. stellatapopulations, and restored populations under different levels of canopy cover, were built from demographic data collected over a four year period. Stochastic models of wild populations projected stable or slightly declining long-term growth rates depending on frequency of dry years. Projected long-term population growth rates of restored populations were significantly higher in closed than open canopy conditions, but indicated population decline under both conditions. Life table response experiments illustrated that lower survival rates, especially of small adults and juveniles, contributed to diminished population growth rates in restored populations. Transient analyses for restored populations projected short-term decline occurring even faster than predicted by asymptotic dynamics. Restored populations will not be viable over the long term under conditions commonly found in restoration projects and interventions will likely be necessary. This study illustrates how the combination of long-term population modelling and transient analyses can be effective in providing relevant information for plant demographers and restoration practitioners to promote self-sustaining native populations, including under future climates.

scholarly journals Founder effects drive the genetic structure of passively dispersed aquatic invertebrates

2018 ◽  
Author(s):  
Javier Montero-Pau ◽  
Africa Gomez ◽  
Manuel Serra
Keyword(s):  
Life Cycle ◽  
Genetic Structure ◽  
Population Growth ◽  
Local Adaptation ◽  
Growth Rates ◽  
High Population ◽  
Founder Effects ◽  
Population Growth Rates ◽  
High Population Growth ◽  
The Impact

Populations of passively dispersed organisms in continental aquatic habitats typically show high levels of neutral genetic differentiation, despite their high dispersal capabilities. Several evolutionary factors, including founder events and local adaptation, and life cycle features such as high population growth rates and the presence of propagule banks, have been proposed to be responsible for this paradox. Here, we have modeled the colonization process in these organisms to assess the impact of migration rate, growth rate, population size, local adaptation and life-cycle features on their population genetic structure. Our simulation results show that the strongest effect on population structure is caused by persistent founder effects, resulting from the interaction of a few population founders, high population growth rates, large population sizes and the presence of diapausing egg banks. In contrast, the role of local adaptation, genetic hitchhiking and migration is limited to small populations in these organisms. Our results indicate that local adaptation could have different impact on genetic structure in different groups of zooplankters.

scholarly journals Effect of mutualist partner identity on plant demography

2014 ◽  
Author(s):  
Emilio M Bruna ◽  
Thiago J Izzo ◽  
Brian D Inouye ◽  
Heraldo L Vasconcelos
Keyword(s):  
Population Growth ◽  
Growth Rates ◽  
Census Data ◽  
Interspecific Variation ◽  
Multiple Partner ◽  
Population Growth Rates ◽  
Crematogaster Laevis ◽  
Asymptotic Growth Rate ◽  
Demographic Effects

Mutualisms play a central role in the origin and maintenance of biodiversity. Because many mutualisms have strong demographic effects, interspecific variation in partner quality could have important consequences for population dynamics. Nevertheless, few studies have quantified how a mutualist partner influences population growth rates, and still fewer have compared the demographic impacts of multiple partner species. We used integral projection models parameterized with three years of census data to compare the demographic effects of two ant species – Crematogaster laevis and Pheidole minutula – on populations of the Amazonian ant-plant Maieta guianensis. Estimated population growth rates were positive (i.e., λ>1) for all ant-plant combinations. However, populations with only Pheidole minutula had the highest asymptotic growth rate (λ=1.23), followed by those colonized by Crematogaster laevis (λ=1.16), and in which the partner ant alternated between C. laevis and P. minutula at least once during our study (λ=1.15). Our results indicate that the short-term superiority of a mutualist partner – in this system P. minutula is a better defender of plants against herbivores than C. laevis – can have long-term demographic consequences. Furthermore, the demographic effects of switching among alternative partners appear to be context-dependent, with no benefits to plants hosting C. laevis but a major cost of switching to plants hosting P. minutula. Our results underscore the importance of expanding the study of mutualisms beyond the study of pair-wise interactions to consider the demographic costs and benefits of interacting with different, and multiple, potential partners.

Road mortality reduces survival and population growth rates of tammar wallabies on Garden Island, Western Australia

2010 ◽  
Vol 37 (7) ◽  
pp. 588 ◽  
Author(s):  
Brian Chambers ◽  
Roberta Bencini
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Western Australia ◽  
Growth Rates ◽  
Survival Rates ◽  
Habitat Modification ◽  
Road Mortality ◽  
Population Growth Rates ◽  
The Impact ◽  
Naval Base

Context Although road mortality has the potential to affect the fate of populations, it is often confounded with other forms of environmental change. Therefore determining its impact separately from other factors is difficult because it requires an understanding of how road mortalities affect age- and sex-specific survival rates. Aims We determined the impact of high numbers of road-kills and habitat modification on the growth and survival of the population of tammar wallabies (Macropus eugenii) on Garden Island, off the coast of Western Australia. The increased supply of food from large areas of fertilised and irrigated lawns on a naval base was expected to increase the population growth rate (λ) and the road-kills were expected to offset the population response. Methods We conducted a mark-and-recapture study over three years to estimate rates of survival, reproduction and population growth rates in areas of the island that were either heavily affected by the presence of a naval base that included a network of roads and buildings, close enough to the naval base that animals could be affected by the disturbance there, and completely unaffected and lacking major roads or buildings. All road-kills were collected to estimate the impact of road mortality on the survival and growth rates of the population. Key results The growth rate, λ, for the population on the naval base was 1.02 ± 0.083 (s.e.) per year, which was much higher than in an area of adjacent bushland at 0.92 ± 0.065 per year and in undisturbed bushland at 0.93 ± 0.100 per year. When the impact of road mortality was removed, λ increased to 1.15 ± 0.101 per year on the naval base and 0.96 ± 0.076 per year in the bushland adjacent to the naval base. On the naval base road mortality reduced survival rates of one-year-old and adult animals by 0.14 ± 0.087 and 0.12 ± 0.012 per year (mean ± s.e.). Conclusions Road mortality counteracted the increase in the size of the tammar population caused by the habitat modification on the naval base. The impact of road mortality on the adjacent bushland population may result in its long-term decline, as the population may not be able to recover from the reduction in survival rates. Implications Road mortality has the potential to threaten susceptible populations but its impact should be quantified so that mitigation measures can be implemented where they will achieve the greatest benefits.

scholarly journals Pattern of variation in avian population growth rates

2002 ◽  
Vol 357 (1425) ◽  
pp. 1185-1195 ◽  
Author(s):  
Bernt–Erik Sæther ◽  
Steinar Engen
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Growth Rates ◽  
Specific Growth ◽  
Population Projections ◽  
Stochastic Effects ◽  
Density Regulation ◽  
Population Growth Rates ◽  
Specific Growth Rates

A central question in population ecology is to understand why population growth rates differ over time. Here, we describe how the long–term growth of populations is not only influenced by parameters affecting the expected dynamics, for example form of density dependence and specific population growth rate, but is also affected by environmental and demographic stochasticity. Using long–term studies of fluctuations of bird populations, we show an interaction between the stochastic and the deterministic components of the population dynamics: high specific growth rates at small densities r 1 are typically positively correlated with the environmental variance σ e 2 . Furthermore, θ, a single parameter describing the form of the density regulation in the theta–logistic density–regulation model, is negatively correlated with r 1 . These patterns are in turn correlated with interspecific differences in life–history characteristics. Higher specific growth rates, larger stochastic effects on the population dynamics and stronger density regulation at small densities are found in species with large clutch sizes or high adult mortality rates than in long–lived species. Unfortunately, large uncertainties in parameter estimates, as well as strong stochastic effects on the population dynamics, will often make even short–term population projections unreliable. We illustrate that the concept of population prediction interval can be useful in evaluating the consequences of these uncertainties in the population projections for the choice of management actions.

scholarly journals Founder effects drive the genetic structure of passively dispersed aquatic invertebrates

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e6094 ◽  
Author(s):  
Javier Montero-Pau ◽  
Africa Gómez ◽  
Manuel Serra
Keyword(s):  
Life Cycle ◽  
Genetic Structure ◽  
Population Growth ◽  
Local Adaptation ◽  
Growth Rates ◽  
High Population ◽  
Founder Effects ◽  
Population Growth Rates ◽  
High Population Growth ◽  
The Impact

Populations of passively dispersed organisms in continental aquatic habitats typically show high levels of neutral genetic differentiation despite their high dispersal capabilities. Several evolutionary factors, including founder events, local adaptation, and life cycle features such as high population growth rates and the presence of propagule banks, have been proposed to be responsible for this paradox. Here, we have modeled the colonization process to assess the impact of migration rate, population growth rate, population size, local adaptation and life-cycle features on the population genetic structure in these organisms. Our simulations show that the strongest effect on population structure are persistent founder effects, resulting from the interaction of a few population founders, high population growth rates, large population sizes and the presence of diapausing egg banks. In contrast, the role of local adaptation, genetic hitchhiking and migration is limited to small populations in these organisms. Our results indicate that local adaptation could have different impact on genetic structure in different groups of zooplankters.

scholarly journals Founder effects drive the genetic structure of passively dispersed aquatic invertebrates

2018 ◽  
Author(s):  
Javier Montero-Pau ◽  
Africa Gomez ◽  
Manuel Serra
Keyword(s):  
Life Cycle ◽  
Genetic Structure ◽  
Population Growth ◽  
Local Adaptation ◽  
Growth Rates ◽  
High Population ◽  
Founder Effects ◽  
Population Growth Rates ◽  
High Population Growth ◽  
The Impact

Populations of passively dispersed organisms in continental aquatic habitats typically show high levels of neutral genetic differentiation, despite their high dispersal capabilities. Several evolutionary factors, including founder events and local adaptation, and life cycle features such as high population growth rates and the presence of propagule banks, have been proposed to be responsible for this paradox. Here, we have modeled the colonization process in these organisms to assess the impact of migration rate, growth rate, population size, local adaptation and life-cycle features on their population genetic structure. Our simulation results show that the strongest effect on population structure is caused by persistent founder effects, resulting from the interaction of a few population founders, high population growth rates, large population sizes and the presence of diapausing egg banks. In contrast, the role of local adaptation, genetic hitchhiking and migration is limited to small populations in these organisms. Our results indicate that local adaptation could have different impact on genetic structure in different groups of zooplankters.

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