The demography of terrestrial orchids: life history, population dynamics and conservation

2019 ◽  
Vol 192 (2) ◽  
pp. 315-332 ◽  
Author(s):  
Richard P Shefferson ◽  
Hans Jacquemyn ◽  
Tiiu Kull ◽  
Michael J Hutchings
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Abiotic Factors ◽  
Adult Life ◽  
Life Cycles ◽  
Individual Plant ◽  
Vital Rates ◽  
Net Reproductive Rate ◽  
Terrestrial Orchids ◽  
The Impact

Abstract Terrestrial orchid life-cycles are complex and dependent on pollinators and mycorrhizal associates. Worldwide, orchid populations are declining because of urbanization, atmospheric nitrogen deposition and climate change. To advance understanding of the factors determining orchid population viability, we review knowledge about orchid demography, life histories and population dynamics. Orchids can produce thousands of seeds, although few survive to reach maturity, with mortality rates declining from juvenile to adult life states. Flowering and fruiting rates vary widely between years, and many populations, especially of deceptive species, are pollen- and seed-limited. Many species have long lifespans and periods of vegetative dormancy and exhibit costs associated with reproduction, sprouting, vegetative dormancy, growth and size. Population growth rates range from 0.50–2.92 (mean: 0.983 ± 0.026). Although vital rates can fluctuate widely between years and be strongly correlated, these correlations have little impact on population dynamics. Variation in spatial density of fungi and microsite quality, limited dispersal and competition generate density dependence in vital rates. Future research should elucidate the roles of biotic and abiotic factors on population dynamics to underpin effective management for conservation. Understanding the impact of idiosyncratic individual plant behaviour on population dynamics will also improve demographic parameter estimation, including population growth rate and net reproductive rate.

scholarly journals Drivers of large-scale spatial demographic variation in a perennial plant

2020 ◽  
Author(s):  
Gesa Römer ◽  
Ditte M. Christiansen ◽  
Hendrik de Buhr ◽  
Kristoffer Hylander ◽  
Owen R. Jones ◽  
...  
Keyword(s):  
Growth Rate ◽  
Population Dynamics ◽  
Environmental Factors ◽  
Population Growth ◽  
Spatial Variation ◽  
Population Growth Rate ◽  
Forest Understory ◽  
Environmental Drivers ◽  
Vital Rates ◽  
The Impact

AbstractTo understand how the environment drives spatial variation in population dynamics, we need to assess the effects of a large number of potential drivers on the vital rates (survival, growth and reproduction), and explore these relationships over large geographical areas and long environmental gradients. In this study, we examined the effects of a broad variety of abiotic and biotic environmental factors, including intraspecific density, on the demography of the forest understory herb Actaea spicata between 2017 and 2019 at 40 sites across Sweden, including the northern range margin of its distribution. We assessed the effect of potential environmental drivers on vital rates using generalized linear mixed models (GLMMs), and then quantified the impact of each important driver on population growth rate (λ) using integral projection models (IPMs). Population dynamics of A. spicata were mostly driven by environmental factors affecting survival and growth, such as air humidity, soil depth and forest tree species composition, and thus those drivers jointly determined the realized niche of the species. Soil pH had a strong effect on the flowering probability, while the effect on population growth rate was relatively small. In addition to identifying specific drivers for A. spicata’s population dynamics, our study illustrates the impact that spatial variation in environmental conditions can have on λ. Assessing the effects of a broad range of potential drivers, as done in this study, is important not only to quantify the relative importance of different drivers for population dynamics but also to understand species distributions and abundance patterns.

scholarly journals Parasitism of Aedes albopictus by Ascogregarina taiwanensis lowers its competitive ability against Aedes triseriatus

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Emma Stump ◽  
Lauren M. Childs ◽  
Melody Walker
Keyword(s):  
Population Dynamics ◽  
Competitive Advantage ◽  
Aedes Albopictus ◽  
Abiotic Factors ◽  
Mosquito Species ◽  
Disease Spread ◽  
Aedes Triseriatus ◽  
La Crosse Virus ◽  
The Impact ◽  
Ascogregarina Taiwanensis

Abstract Background Mosquitoes are vectors for diseases such as dengue, malaria and La Crosse virus that significantly impact the human population. When multiple mosquito species are present, the competition between species may alter population dynamics as well as disease spread. Two mosquito species, Aedes albopictus and Aedes triseriatus, both inhabit areas where La Crosse virus is found. Infection of Aedes albopictus by the parasite Ascogregarina taiwanensis and Aedes triseriatus by the parasite Ascogregarina barretti can decrease a mosquito’s fitness, respectively. In particular, the decrease in fitness of Aedes albopictus occurs through the impact of Ascogregarina taiwanensis on female fecundity, larval development rate, and larval mortality and may impact its initial competitive advantage over Aedes triseriatus during invasion. Methods We examine the effects of parasitism of gregarine parasites on Aedes albopictus and triseriatus population dynamics and competition with a focus on when Aedes albopictus is new to an area. We build a compartmental model including competition between Aedes albopictus and triseriatus while under parasitism of the gregarine parasites. Using parameters based on the literature, we simulate the dynamics and analyze the equilibrium population proportion of the two species. We consider the presence of both parasites and potential dilution effects. Results We show that increased levels of parasitism in Aedes albopictus will decrease the initial competitive advantage of the species over Aedes triseriatus and increase the survivorship of Aedes triseriatus. We find Aedes albopictus is better able to invade when there is more extreme parasitism of Aedes triseriatus. Furthermore, although the transient dynamics differ, dilution of the parasite density through uptake by both species does not alter the equilibrium population sizes of either species. Conclusions Mosquito population dynamics are affected by many factors, such as abiotic factors (e.g. temperature and humidity) and competition between mosquito species. This is especially true when multiple mosquito species are vying to live in the same area. Knowledge of how population dynamics are affected by gregarine parasites among competing species can inform future mosquito control efforts and help prevent the spread of vector-borne disease.

scholarly journals Linking individual phenotype to density-dependent population growth: the influence of body size on the population dynamics of malaria vectors

2011 ◽  
Vol 278 (1721) ◽  
pp. 3142-3151 ◽  
Author(s):  
Tanya L. Russell ◽  
Dickson W. Lwetoijera ◽  
Bart G. J. Knols ◽  
Willem Takken ◽  
Gerry F. Killeen ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Body Size ◽  
Population Growth ◽  
Vector Control ◽  
Anopheles Gambiae ◽  
Phenotypic Expression ◽  
Phenotypic Traits ◽  
Density Dependent ◽  
Individual Fitness ◽  
The Impact

Understanding the endogenous factors that drive the population dynamics of malaria mosquitoes will facilitate more accurate predictions about vector control effectiveness and our ability to destabilize the growth of either low- or high-density insect populations. We assessed whether variation in phenotypic traits predict the dynamics of Anopheles gambiae sensu lato mosquitoes, the most important vectors of human malaria. Anopheles gambiae dynamics were monitored over a six-month period of seasonal growth and decline. The population exhibited density-dependent feedback, with the carrying capacity being modified by rainfall (97% w AIC c support). The individual phenotypic expression of the maternal ( p = 0.0001) and current ( p = 0.040) body size positively influenced population growth. Our field-based evidence uniquely demonstrates that individual fitness can have population-level impacts and, furthermore, can mitigate the impact of exogenous drivers (e.g. rainfall) in species whose reproduction depends upon it. Once frontline interventions have suppressed mosquito densities, attempts to eliminate malaria with supplementary vector control tools may be attenuated by increased population growth and individual fitness.

Variation in life-cycle between three rare and endangered floodplain violets in two regions: implications for population viability and conservation

Biologia ◽  
2009 ◽  
Vol 64 (1) ◽  
Author(s):  
Rolf Eckstein ◽  
Jiří Danihelka ◽  
Annette Otte
Keyword(s):  
Species Conservation ◽  
Reproductive Rate ◽  
Population Viability ◽  
Life Cycles ◽  
Habitat Destruction ◽  
Vital Rates ◽  
Net Reproductive Rate ◽  
Demographic Traits ◽  
Unequivocal Identification ◽  
Rare And Endangered

AbstractWe studied the demography of Viola elatior, V. pumila, and V. stagnina, three rare and endangered Central European floodplain species, to (i) analyse variation in life-cycles among congeners and between regions (Dyje-Morava floodplains, Czech Republic; Upper Rhine, Germany), (ii) to define sensitive stages in the life-cycles, and (iii) to identify possible threats for population viability and species conservation.Matrix models were based on the fate of marked individuals from a total of 27 populations over two years. We analysed population growth rate (λ), stage distribution, net reproductive rate (R 0), generation time, age at first reproduction, and elasticity and calculated a life table response experiment (LTRE).Most populations were declining and λ did not differ between species or regions during the observed interval. Despite higher probabilities for survival and flowering in the Dyje populations, R 0 was higher in the Rhine populations. Also other demographic traits showed consistent differences between regions and/or species. Complex life-cycles and large variation in λ precluded unequivocal identification of sensitive stages or vital rates for conservation. Variation between regions may be a consequence of differences in habitat quality.Our results suggest that deterministic processes such as reduced management, succession, habitat destruction, and lack of disturbance through reduced or eliminated flooding present the strongest threat for the viability and persistence of populations of the three floodplain violets as compared with stochastic processes. However, the persistent seed bank of the species may buffer populations against environmental variation and represents a reservoir for recovery after resumption of suitable land-use management.

scholarly journals Biotic and Abiotic Factors Affecting the Population Dynamics of Ceratium hirundinella, Peridinium cinctum, and Peridiniopsis elpatiewskyi

Diversity ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 137
Author(s):  
Behrouz Zarei Darki ◽  
Alexandr F. Krakhmalnyi
Keyword(s):  
Population Dynamics ◽  
Abiotic Factors ◽  
Sulfate Ion ◽  
Temperature Conductivity ◽  
Factors Affecting ◽  
Ceratium Hirundinella ◽  
Peridinium Cinctum ◽  
Abiotic And Biotic Factors ◽  
The Impact

The present research was conducted to assess the impact of abiotic and biotic factors on the growth of freshwater dinoflagellates such as Ceratium hirundinella, Peridinium cinctum, and Peridiniopsis elpatiewskyi, which reduce the quality of drinking water in the Zayandeh Rud Reservoir. To this end, 152 algal and zoological samples were collected from the reservoir located in the Central part of Iran in January, April, July, and October 2011. Abiotic factors such as pH, temperature, conductivity, transparency, dissolved oxygen, and nutrient concentration of the water were measured in all study stations. The results showed that the population dynamics of dinoflagellates in the Zayandeh Rud Reservoir was different depending on season, station, and depth. The findings proved that C. hirundinella was one of the dominant autumn planktons in the highest biovolume in the Zayandeh Rud Reservoir. While P. elpatiewskyi was present in the reservoir throughout a year with biovolume peak in summer. Accompanying bloom of P. elpatiewskyi and C. hirundinella, P. cinctum also grew in well-heated summer and autumn waters. It was further found that Ceratium density was positively correlated with sulfate ion concentrations, while the growth of P. cinctum and P. elpatiewskyi were associated, first and foremost, with NO2− and Mn.

scholarly journals Parasitism of Aedes albopictus by Ascogregarina taiwanensis lowers its competitive ability against Aedes triseriatus.

2020 ◽  
Author(s):  
Emma Stump ◽  
Lauren M Childs ◽  
Melody Walker
Keyword(s):  
Population Dynamics ◽  
Competitive Advantage ◽  
Aedes Albopictus ◽  
Abiotic Factors ◽  
Mosquito Species ◽  
Disease Spread ◽  
Aedes Triseriatus ◽  
La Crosse Virus ◽  
The Impact ◽  
Ascogregarina Taiwanensis

Abstract Background: Mosquitoes are vectors for diseases that significantly impact the human population such as dengue, malaria and La Crosse virus. When multiple mosquito species are present, the competition between species may alter population dynamics as well as disease spread. Two mosquito species, Aedes albopictus and Aedes triseriatus, both inhabit areas where La Crosse virus is found. Infection of Aedes albopictus by the parasite Ascogregarina taiwanensis and Aedes triseriatus by the parasite Ascogregarina barretti can decrease a mosquito’s fitness, respectively. In particular, the decrease in fitness of Aedes albopictus occurs through the impact of Ascogregarina taiwanensis on female fecundity, larval development rate, and larval mortality and may impact its initial competitive advantage over Aedes triseriatus during invasion.Methods: We examine the effects of parasitism of gregarine parasites on Aedes albopictus and triseriatus population dynamics and competition with a focus on when Aedes albopictus is new to an area. We build a compartmental model including competition between Aedes albopictus and triseriatus while under parasitism of the gregarine parasites. Using parameters based on literature, we simulate the dynamics and analyze the equilibrium population proportion of the two species. We consider the presence of both parasites and potential dilution effects.Results: We show that increased levels of parasitism in Aedes albopictus will decrease the initial competitive advantage of the species over Aedes triseriatus and increase the survivorship of Aedes triseriatus. We find Aedes albopictus is better able to invade when there is more extreme parasitism of Aedes triseriatus. Furthermore, although the transient dynamics differ, dilution of the parasite density through uptake by both species does not alter the equilibrium population sizes of either species.Conclusions: Mosquito population dynamics are affected by many factors, such as abiotic factors (e.g. temperature and humidity) and competition between mosquito species. This is especially true when multiple mosquito species are vying to live in the same area. Knowledge of how population dynamics are affected by gregarine parasites among competing species can inform future mosquito control efforts and help prevent the spread of vector-borne disease.

Seasonal Population Dynamics of Potato Psyllid (Hemiptera: Triozidae) in the Columbia River Basin

2020 ◽  
Vol 49 (4) ◽  
pp. 974-982
Author(s):  
Abigail L Cohen ◽  
Carrie H Wohleb ◽  
Silvia I Rondon ◽  
Kylie D Swisher Grimm ◽  
Isabel Cueva ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Abiotic Factors ◽  
Insect Pest ◽  
Pest Species ◽  
Potato Psyllid ◽  
Bactericera Cockerelli ◽  
Weather Patterns ◽  
Degree Day ◽  
Seasonal Weather

Abstract Understanding factors that affect the population dynamics of insect pest species is key for developing integrated pest management strategies in agroecosystems. Most insect pest populations are strongly regulated by abiotic factors such as temperature and precipitation, and assessing relationships between abiotic conditions and pest dynamics can aid decision-making. However, many pests are also managed with insecticides, which can confound relationships between abiotic factors and pest dynamics. Here we used data from a regional monitoring network in the Pacific Northwest United States to explore effects of abiotic factors on populations of an intensively managed potato pest, the potato psyllid (Bactericera cockerelli Šulc), which can vector Candidatus Liberibacter psyllaurus, a bacterial pathogen of potatoes. We assessed effects of temperature on psyllid populations, and show psyllid population growth followed predictable patterns within each year, but there was considerable variation across years in psyllid abundance. Examination of seasonal weather patterns suggested that in 2017, when psyllid populations were less abundant by several orders of magnitude than other years, a particularly long and cold period of winter weather may have harmed overwintering populations and limited population growth. The rate of degree-day accumulation over time, as well as total degree-day accumulation also affected trap catch abundance, likely by mediating the number of psyllid generations per season. Our findings indicate that growers can reliably infer the potential magnitude of risk from potato psyllids using monitoring data, date of first detection, seasonal weather patterns, and population size early in the growing season.

scholarly journals Early snowmelt projected to cause population decline in a subalpine plant

2019 ◽  
Vol 116 (26) ◽  
pp. 12901-12906 ◽  
Author(s):  
Diane R. Campbell
Keyword(s):  
Climate Change ◽  
Population Growth ◽  
Seed Production ◽  
Demographic Data ◽  
Population Decline ◽  
Floral Display ◽  
Vital Rates ◽  
Flower Number ◽  
Early Snowmelt ◽  
The Impact

How climate change influences the dynamics of plant populations is not well understood, as few plant studies have measured responses of vital rates to climatic variables and modeled the impact on population growth. The present study used 25 y of demographic data to analyze how survival, growth, and fecundity respond to date of spring snowmelt for a subalpine plant. Fecundity was estimated by seed production (over 15 y) and also divided into flower number, fruit set, seeds per fruit, and escape from seed predation. Despite no apparent effects on flower number, plants produced more seeds in years with later snowmelt. Survival and probability of flowering were reduced by early snowmelt in the previous year. Based on demographic models, earlier snowmelt with warming is expected to lead to negative population growth, driven especially by changes in seedling establishment and seed production. These results provide a rare example of how climate change is expected to influence the dynamics of a plant population. They furthermore illustrate the potential for strong population impacts even in the absence of more commonly reported visual signs, such as earlier blooming or reduced floral display in early melting years.

scholarly journals What are the demographic consequences of a seed bank stage for columnar cacti?

2020 ◽  
Author(s):  
Gabriel Arroyo-Cosultchi ◽  
María C. Mandujano ◽  
Roberto Salguero-Gómez ◽  
Armando J. Martínez ◽  
Jordan Golubov
Keyword(s):  
Population Dynamics ◽  
Plant Species ◽  
Seed Bank ◽  
Seedling Recruitment ◽  
Early Stage ◽  
Life Cycles ◽  
Vital Rates ◽  
Matrix Population Models ◽  
Columnar Cacti ◽  
Seed Bank Dynamics

AbstractThe dynamics of plants populations are often limited by the early stages in their life cycles. The question if the columnar cacti have or not a seed bank in predictable environments. Yet, information regarding seed bank dynamics and how these may influence the full life cycle of plant species is remarkably scarce or ignore. This lack of knowledge is mostly due to the challenges in quantifying seed vital rates. Studies of arid land plant species have historically been focused on the drivers of sporadic recruitment. However, little attention has been given to the demographic consequences of early developmental stages, including seed banks. Here, we evaluate the effects of seed bank survival and seedling recruitment vital rates on the population dynamics and viability of 12 columnar cacti species, recent evidence suggests that cacti seeds may remain viable for the short-term. We assess how changes in the vital rates of these processes, and the inclusion of a seed bank affect population growth rate (λ). We found that a seed bank in the examined matrix population models significantly increased λ as well as the vital rate elasticities of λ to growth and fecundity, whereas that of overall survival decreased. Our numerical simulations showed that seed survival had a larger effect on λ than seedling recruitment and establishment. We suggest that seed bank may explain the structure and population dynamics. Thus, we argue reconsider that this early stage in demographic models will generate more informed decisions on the conservation and management of columnar cacti.

scholarly journals Size-by-environment interactions: a neglected dimension of species’ responses to environmental variation

2018 ◽  
Author(s):  
Andrew T. Tredennick ◽  
Brittany J. Teller ◽  
Peter B. Adler ◽  
Giles Hooker ◽  
Stephen P. Ellner
Keyword(s):  
Population Dynamics ◽  
Functional Form ◽  
Survival Rates ◽  
Vital Rate ◽  
Vital Rates ◽  
Size Dependent ◽  
Fluctuating Environments ◽  
The Impact ◽  
The Relationship

AbstractIn both plant and animal systems, size can determine whether an individual survives and grows under different environmental conditions. However, it is less clear whether and when size-dependent responses to the environment affect population dynamics. Size-by-environment interactions create pathways for environmental fluctuations to influence population dynamics by allowing for negative covariation between sizes within vital rates (e.g., small and large individuals have negatively covarying survival rates) and/or size-dependent variability in a vital rate (e.g., survival of large individuals varies less than small individuals through time). Whether these phenomena affect population dynamics depends on how they are mediated by elasticities (they must affect the sizes and vital rates that matter) and their projected impacts will depend on model functional form (the impact of reduced variance depends on the relationship between the environment and vital rate). We demonstrate these ideas with an analysis of fifteen species from five semiarid plant communities. We find that size-by-environment interactions are common but do not impact long-term population dynamics. Size-by-environment interactions may yet be important for other species. Our approach can be applied to species in other ecosystems to determine if and how size-by-environment interactions allow them to cope with, or exploit, fluctuating environments.

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