scholarly journals Six-Year Demographic Study of the Terrestrial Orchid, Crepidium acuminatum: Implications for Conservation

2021 ◽  
Vol 9 ◽  
Author(s):  
Binu Timsina ◽  
Pavel Kindlmann ◽  
Zuzana Münzbergová ◽  
Maan B. Rokaya
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Management Strategies ◽  
Natural Populations ◽  
Important Species ◽  
Growth And Survival ◽  
Population Growth Rates ◽  
Matrix Modeling ◽  
Species Population ◽  
Medicinal Orchid

Studies on population dynamics are helpful for understanding the factors determining population development and predicting the effects of disturbances, such as harvesting of plant species. In an investigation of the demography of a terrestrial medicinal orchid known as Crepidium acuminatum, the effects of harvesting on its population dynamics were recorded. Data on recruitment, growth and survival were collected in three populations of C. acuminatum over a 6-year period (2012–2017) in central Nepal. A matrix modeling method was used to determine the effect of different harvesting regimes on the population growth and survival of this species. Population growth rates (λ) of unharvested populations were relatively similar and stable in different years of the study. Harvesting significantly reduced λ. The results of this study indicate that the sustainable survival of a population that is subject to harvesting can only occur when it is either selective (only flowering individuals or only small amounts of vegetative individuals) or rotational (once every 3–5 or more years). This study demonstrates the necessity of using a sustainable method when harvesting natural populations. Our results are useful for developing efficient management strategies for this species. As each species has a different biology, similar studies are needed for other rare and/or economically important species in the Himalayan region and in other understudied parts of the world.

Life history and environmental influences on population dynamics in sockeye salmon

2014 ◽  
Vol 71 (8) ◽  
pp. 1198-1208 ◽  
Author(s):  
Douglas C. Braun ◽  
John D. Reynolds
Keyword(s):  
Population Dynamics ◽  
Life History ◽  
Population Growth ◽  
Growth Rates ◽  
Environmental Conditions ◽  
Sockeye Salmon ◽  
Life History Traits ◽  
Relative Importance ◽  
Population Growth Rates ◽  
Habitat Variables

Understanding linkages among life history traits, the environment, and population dynamics is a central goal in ecology. We compared 15 populations of sockeye salmon (Oncorhynchus nerka) to test general hypotheses for the relative importance of life history traits and environmental conditions in explaining variation in population dynamics. We used life history traits and habitat variables as covariates in mixed-effect Ricker models to evaluate the support for correlates of maximum population growth rates, density dependence, and variability in dynamics among populations. We found dramatic differences in the dynamics of populations that spawn in a small geographical area. These differences among populations were related to variation in habitats but not life history traits. Populations that spawned in deep water had higher and less variable population growth rates, and populations inhabiting streams with larger gravels experienced stronger negative density dependence. These results demonstrate, in these populations, the relative importance of environmental conditions and life histories in explaining population dynamics, which is rarely possible for multiple populations of the same species. Furthermore, they suggest that local habitat variables are important for the assessment of population status, especially when multiple populations with different dynamics are managed as aggregates.

scholarly journals Weather influences M. arvalis reproduction but not population dynamics in a 17-year time series

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Patrick Giraudoux ◽  
Petra Villette ◽  
Jean-Pierre Quéré ◽  
Jean-Pierre Damange ◽  
Pierre Delattre
Keyword(s):  
Time Series ◽  
Population Dynamics ◽  
Population Growth ◽  
Growth Rates ◽  
Demographic Data ◽  
Common Vole ◽  
Empirical Work ◽  
Weather Conditions ◽  
Female Reproduction ◽  
Population Growth Rates

Abstract Rodent outbreaks have plagued European agriculture for centuries, but continue to elude comprehensive explanation. Modelling and empirical work in some cyclic rodent systems suggests that changes in reproductive parameters are partly responsible for observed population dynamics. Using a 17-year time series of Microtus arvalis population abundance and demographic data, we explored the relationship between meteorological conditions (temperature and rainfall), female reproductive activity, and population growth rates in a non-cyclic population of this grassland vole species. We found strong but complex relationships between female reproduction and climate variables, with spring female reproduction depressed after cold winters. Population growth rates were, however, uncorrelated with either weather conditions (current and up to three months prior) or with female reproduction (number of foetuses per female and/or proportion of females reproductively active in the population). These results, coupled with age-structure data, suggest that mortality, via predation, disease, or a combination of the two, are responsible for the large multi-annual but non-cyclic population dynamics observed in this population of the common vole.

scholarly journals Evolutionary effects of density-dependent selection in plants

1993 ◽  
Vol 62 (1) ◽  
pp. 57-62 ◽  
Author(s):  
G. Namkoong ◽  
J. Bishir ◽  
J. H. Roberds
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Growth Rates ◽  
Energy Allocation ◽  
Gene Frequencies ◽  
Population Growth Rates ◽  
Stable Periodic ◽  
Density Dependent Selection ◽  
Allocation Strategies ◽  
Periodic Changes

SummaryThe evolution of traits that affect genotypic responses to density regulated resources can be strongly affected by population dynamics in ways that are unpredictable from individual viability or reproduction potentials. Genotypes that are most efficient in utilizing energy may not always displace less efficient ones, and the evolution of energy allocation strategies may not always favour reproductive fitness because of their effects on destabilizing population growth rates. Furthermore, genetic polymorphisms in single loci that affect such traits can be maintained in populations with stable, periodic changes in population size and gene frequencies in the absence of heterozygote superiority. In fact, in the models investigated in this paper, the polymorphism is maintained, even in the absence of equilibrium genotypic frequencies.

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 Population growth rates: issues and an application

2002 ◽  
Vol 357 (1425) ◽  
pp. 1307-1319 ◽  
Author(s):  
H. Charles J. Godfray ◽  
Mark Rees
Keyword(s):  
Growth Rate ◽  
Population Dynamics ◽  
Population Growth ◽  
Growth Rates ◽  
Population Growth Rate ◽  
Population Change ◽  
Evolutionarily Stable Strategy ◽  
Model Systems ◽  
Population Growth Rates

Current issues in population dynamics are discussed in the context of The Royal Society Discussion Meeting 'Population growth rate: determining factors and role in population regulation'. In particular, different views on the centrality of population growth rates to the study of population dynamics and the role of experiments and theory are explored. Major themes emerging include the role of modern statistical techniques in bringing together experimental and theoretical studies, the importance of long-term experimentation and the need for ecology to have model systems, and the value of population growth rate as a means of understanding and predicting population change. The last point is illustrated by the application of a recently introduced technique, integral projection modelling, to study the population growth rate of a monocarpic perennial plant, its elasticities to different life-history components and the evolution of an evolutionarily stable strategy size at flowering.

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 Potential for Acanthoscelides obtectus to Adapt to New Hosts Seen in Laboratory Selection Experiments

Insects ◽  
2019 ◽  
Vol 10 (6) ◽  
pp. 153
Author(s):  
Uroš Savković ◽  
Mirko Đorđević ◽  
Biljana Stojković
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Host Plant ◽  
Mung Bean ◽  
Good Practice ◽  
Pest Species ◽  
Acanthoscelides Obtectus ◽  
New Host ◽  
Important Species ◽  
Laboratory Selection

Effective pest management strategies for a targeted pest species must rely on accurate, reliable and reproducible estimates of population dynamics. Importance of such approaches is even more conspicuous when assessing pest’s potential to utilize other stored products. Using an experimental evolution approach, we have focused our attention on a common bean pest, the seed beetle (Acanthoscelides obtectus). We looked into the potential to invade and sustain population growth on two suboptimal host plants (chickpeas and mung beans). Such an approach simulates steps of the host-shift process in storages. By analyzing population dynamics during initial encountering with a new host plant, we detected a population drop for both novel hosts. However, transgenerational development in a novel environment resulted in a constant population growth in chickpeas, but not in mung bean populations. Reversal of chickpea selected populations to original host plant has led to a severe decrease in population parameters due to low viability of immatures, while the opposite trend was detected in mung bean populations. This paper highlights the importance of good practice in estimating population dynamics for economically important species. With special emphasis on storage pest species, we discuss how this approach can be useful for estimating invading potential of pest insects.

Mycetophagy in Filenchus misellus (Andrássy, 1958) Lownsbery & Lownsbery, 1985 (Nematoda: Tylenchidae), with notes on its morphology

Nematology ◽  
2002 ◽  
Vol 4 (7) ◽  
pp. 795-801 ◽  
Author(s):  
Ikuo Kadota ◽  
Takao Tsukiboshi ◽  
Hiroaki Okada
Keyword(s):  
Population Growth ◽  
Growth Rates ◽  
Agaricus Bisporus ◽  
Morphological Characteristics ◽  
Pythium Ultimum ◽  
Fungal Species ◽  
Life History Strategies ◽  
Population Growth Rates ◽  
Species Population ◽  
Northern Japan

AbstractPopulation growth rates on fungal colonies and morphological characteristics were investigated in a member of the genus Filenchus (Tylenchidae) collected from decomposing rice straw in Fukushima-city, northern Japan. The nematode was identified as F. misellus on the basis of the great similarity in morphological measurements to the known populations of the species. Population growth rates were measured 40 days after inoculating nematodes on to seven fungal species cultured in Petri dishes at 25oC. Growth rates were high on Chaetomium globosum and Coprinus cinereus, intermediate on Pleurotus ostreatus and Rhizoctonia solani and low on Agaricus bisporus, Fusarium oxysporum and Pythium ultimum. The ability of the nematode to feed on fungi in decomposing organic matter suggests the possibility for alternative life history strategies and greater ecological amplitude for members of Filenchus and other genera of Tylenchidae.

Demography of Machaerium cuspidatum, a shade-tolerant neotropical liana

2004 ◽  
Vol 20 (5) ◽  
pp. 505-516 ◽  
Author(s):  
Jacob Nabe-Nielsen
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Population Growth Rate ◽  
Woody Species ◽  
Canopy Openness ◽  
Lower Growth ◽  
Growth And Survival ◽  
Population Growth Rates ◽  
Long Time ◽  
Slow Growing

The population dynamics of the liana Machaerium cuspidatum (Fabaceae) were studied in an Amazonian forest in Ecuador using a stage-classified matrix model. Growth, mortality and number of new seedlings were recorded over two 1.5-y periods in eight 20 × 250-m transects. The population growth rate (λ) was 1.032, which was significantly higher than 1. The dynamics of the species were most influenced by survival of large plants, which is typical for slow-growing woody species. λ varied little among years or transects in spite of the high seedling production in one period. The importance of canopy openness and crown height for population growth was studied using bootstraps on λ for different subsets of the whole population. The results suggest that the population growth rate was lower in tall forest (height > 10 m) than in the population in general. The population growth rates in areas with shaded understorey and in low forest (≤ 20 m) were the same as for the whole population. A life table response experiment (LTRE) revealed that the lower λ in tall forest resulted from lower growth and survival of large plants in tall forest. These results indicate that the species is shade-tolerant but that it is sensitive to variations in forest dynamics. The dominance of the species and the increasing population size suggest that the forest has had a low disturbance rate for a long time.

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