Peaks Of Population Density Research Articles

Population Density of Bemisia tabaci on Sweet Pepper (Capsicum annuum) Varieties in the Greenhouse

We conducted an experiment in a greenhouse at the research station belonging to the Department of Plant Protection / Ministry of Agriculture, in Abu Ghraib area during the spring and autumn season 2022-2023, to study the population density of the whitefly on two varieties of sweet pepper plant (Charisma and Sierra Nevada). The experiment was laid out in a randomized complete block design “RCBD” with three replicates for each variety. The results showed that in spring season the population density of B. tabaci eggs and nymphs reached the peak in the last week of May, which where 2.667 and 4.444 individual / leaf, respectively while the population density peak of the adults was in the first week of June, where it reached 3.33 individual / leaf for Charisma variety, while in Sierra Nevada variety the population density of eggs reached its peak at the first week of May 2.889 individual / leaf, while the nymphs reached its peak at the last week of May 4.44 individual / leaf, also the adults reached its peak the in the second week of June 2.667 individual / leaf. In autumn season the population density of the eggs, nymphs and adults on Charisma variety reached its peak in the third week of November, where it were 3.556, 2.778 and 3.444 individual / leaf respectively, while the population density of the eggs, nymphs and adults recorded on the Sierra Nevada variety reached its peak in the third week of November with 3.889, 3.778 and 3.778 individual / leaf respectively. These results clearly showed that B. tabaci had nearly the same preference to infest the two varieties of sweet pepper, Charisma and Sierra Nevada through the abundance of their stages on the plants.

Lack of detectable genetic isolation in the cyclic rodent Microtus arvalis despite large landscape fragmentation owing to transportation infrastructures

Although roads are widely seen as dispersal barriers, their genetic consequences for animals that experience large fluctuations in population density are poorly documented. We developed a spatially paired experimental design to assess the genetic impacts of roads on cyclic voles (Microtus arvalis) during a high-density phase in North-Western Spain. We compared genetic patterns from 15 paired plots bisected by three different barrier types, using linear mixed models and computing effect sizes to assess the importance of each type, and the influence of road features like width or the age of the infrastructure. Evidence of effects by roads on genetic diversity and differentiation were lacking. We speculate that the recurrent (each 3–5 generations) episodes of massive dispersal associated with population density peaks can homogenize populations and mitigate the possible genetic impact of landscape fragmentation by roads. This study highlights the importance of developing spatially replicated experimental designs that allow us to consider the large natural spatial variation in genetic parameters. More generally, these results contribute to our understanding of the not well explored effects of habitat fragmentation on dispersal in species showing “boom-bust” dynamics.

THE POPULATION OF WHITE-BELLIED PLANTHOPPERS AND THEIR NATURAL ENEMIES: THE NEW PEST OF CORN IN LAMPUNG

The Population of White-Bellied Planthoppers and their Natural Enemies: the New Pest of Corn in Lampung. The white-bellied planthoppers (Stenocranus pasificus), hereinafter referred to as WBP, as new exotic pests in Lampung have the poten-tial to reduce corn production and threaten national food sovereignty. Therefore, population of the pest needs to be managed to prevent the outbreaks. However, there is still limited information on the bio-ecology of WBP. Thus, this research was conducted to: 1) study the population growth pattern of WBP on various corn cultivars and 2) document the natural enemies of WBP. This research was carried out from May to December 2017with a survey method on several corn fields in South Lampung and planting trial on an experimental field of Faculty of Agriculture, Universitas Lampung planted with 3 corn cultivars, i.e. Madura, P-27 and NK which were arranged in randomized complete block design with three replications. The results of the research showed: 1) there were two peaks of population density observed during plant growth. The peak of adult stage of macroptera population density occurred at 17 and 53 days after planting (dap), the highest number of leaves with oviposition mass was observed at 24 and 65 dap, while the peak of population density of nymph stage and adult stage of brachiptera occurred at 31 and 75 dap; 2) Natural enemies of WBP included 9 orders, classified as specialist predators of mirid bugs (Cyrtorhynus) and rove beetles (Paederus), and generalist predators of spiders (Araneae) and lady beetles (Coccinellidae). The population of specialist predators was fluctuated depending on WBP population, while the population of generalist predators was varied.

EFFECT OF CERTAIN WEATHER FACTORS AND SOME NATURAL ENEMIES ON THE POPULATION DENSITY OF THE BOLLWORMS AND COTTON LEAFWORM AT KAFR EL-SHEIKH GOVERNORATE, EGYPT

Experiments were carried out at the Farm of Sakha Agricultural Research Station Kafr El-Sheikh Governorate, during two successive seasons, 2014 and 2015 to evaluate the effect of certain weather factors (temperature, relative humidity and wind speed), and some natural enemies (six insect predators were recorded, Coccinella undecimpunctata L., Scymnus interruptus Goez., Paederus alfierii Koch, Syrphus spp., Orius spp. and Chrysoperlla carnea (Steph.))on the population density of the bollworms larvae (pink bollworm, Pectinophora gossypiella (Saund.) and spiny bollworm, Earias insulana (Boisd.) and the egg-masses of the cotton leafworm, Spodoptera littoralis (Boisd.). The initial occurrence of the pink bollworm larvae on cotton bolls was recorded in the last week of July (26th) during the first season and week early (18th of July) during the second season and exhibited four peaks of population density in every season. Numbers of larvae were highly significant and negative correlated with changes of the temperature (-0.752** and -0.798**) of both seasons, respectively. While, the correlation between numbers of larvae and changes of the relative humidity was insignificantly and negatively (-0.103 and -0.140) in both seasons, respectively. But, the wind speed influenced on the larval occurrence were significant and negative (-0.472*) during the first season, and insignificant and positive (0.020) during the second season. So, the correlation were positive and significant (0.495* and 0.480*) between the density of larvae of pink bollworm and the insect predators during the two seasons, respectively. While, the initial occurrence of the spiny bollworm larvae on cotton bolls was recorded in the 9th and 15th of August during the two successive seasons, respectively, and exhibited three peaks of population density in every season, number of larvae of this insect was highly significant and negative correlated (-0.631** and -0.690**) with changes of the temperature during both seasons, respectively. While, the relationship between the relative humidity and number of the spiny bollworm larvae was negative and insignificant (-0.177) during the first season, but, it was positive and insignificant (0.083) during the second season, while, the wind speed influenced was significant and negative (-0.408*) during the first season, and it was insignificant and negative (-0.173) during the second season, on the larval occurrence of this insect. So, the correlation were positive and significant (0.542* and 0.585*) between density of the spiny bollworm and the insect predators during the two seasons, respectively. The cotton leaf worm egg-masses exhibited three peaks of population density in every season, the effect of temperature on the population density of the cotton leaf worm egg-masses was significant and positive (0.459*) during the first season, and insignificant and positive (0.212) during the second season, while, the effect of the relative humidity on egg-masses of this insect was insignificant and positive (0.347) during the first season, and negative (-0.134) during the second season. So, the effect of wind speed on egg-masses was insignificant and negative (-0.162) during the first season, and positive (0.263) during the second season. While, the correlation were highly significant and positive (0.631** and 0.620**) between the population density of cotton leaf worm egg-masses and the insect predators during the two successive seasons.

Long-term monitoring and population dynamics of ixodid ticks in Tomsk city (Western Siberia).

Monitoring of two tick species (Ixodes persulcatus Schulze 1930 and Ixodes pavlovskyi Pomerantsev) was performed in four city parks of Tomsk, Russia (Camp Garden, University Park, Southern Cemetery, and Polytechnic Stadium) and in a control wild biotope in city environs (Kolarovo) in 2002-2013. Ticks were collected by flagging repeatedly after each 10 ± 1 days, starting from the disappearance of the snow cover till the end of tick activity (April-August). Gradual penetration of both tick species into city parks was demonstrated. In the wild biotope, I. persulcatus dominated during the whole period of monitoring, forming about 95% of tick population, whereas in urban biotopes I. pavlovskyi became the dominant species. Two peaks of population density during each season of spring-summer activity were observed in both species. Possible explanations of the phenomena are discussed.

Inter-annual climate variability and zooplankton: applying teleconnection indices to two deep subalpine lakes in Italy

Investigating relation between meteo-climatic indices and between-year variation in Daphnia population density and phenology is crucial for e.g. predicting impact of climate change on lake ecosystem structure and functioning. We tested whether and how two teleconnection indices calculated for the winter period, namely the East Atlantic pattern (EADJF) and the Eastern Mediterranean Pattern (EMPDJF) were correlated with Daphnia population growth in two Italian subalpine lakes, Garda and Maggiore. We investigated between-lake temporal coherence in: i) water temperature within the water layer in which Daphnia is distributed; ii) timing of Daphnia initial and spring maximum population density peak and iii) the level of Daphnia spring maximum population density peak over an eleven-year period (1998-2008) of unchanged predation pressure by fish and invertebrates, and of common oligotrophy. Between-lake temporal coherence was high for an earlier start, an earlier, and lower, Daphnia population spring density peak after milder winters. Peak density level was coherently, positively correlated with soluble reactive phosphorus (SRP) concentration. We hypothesized that Daphnia peak densities were related to atmospheric modes of variability in winter and to the degree of late winter mixing promoting replenishment of algal nutrients into upper water layers and phytoplankton growth, enhancing food availability and Daphnia fecundity, promoting Daphnia peak.

Diet Quality Limits Summer Growth of Field Vole Populations

Marked variation occurs in both seasonal and multiannual population density peaks of northern European small mammal species, including voles. The availability of dietary proteins is a key factor limiting the population growth of herbivore species. The objective of this study is to investigate the degree to which protein availability influences the growth of increasing vole populations. We hypothesise that the summer growth of folivorous vole populations is positively associated with dietary protein availability. A field experiment was conducted over a summer reproductive period in 18 vegetated enclosures. Populations of field voles (Microtus agrestis) were randomised amongst three treatment groups: 1) food supplementation with ad libitum high protein (30% dry weight) pellets, 2) food supplementation with ad libitum low protein (1% dry weight; both supplemented foods had equivalent energy content) pellets, and 3) control (no food supplementation), n = 6 per treatment. Vole density, survival, demographic attributes and condition indicators were monitored with live-trapping and blood sampling. Highest final vole densities were attained in populations that received high protein supplementation and lowest in low protein populations. Control populations displayed intermediate densities. The survival rate of voles was similar in all treatment groups. The proportion of females, and of those that were pregnant or lactating, was highest in the high protein supplemented populations. This suggests that variation in reproductive, rather than survival rates of voles, accounted for density differences between the treatment groups. We found no clear association between population demography and individual physiological condition. Our results demonstrate that dietary protein availability limits vole population growth during the summer growing season. This suggests that the nutritional quality of forage may be an underestimated source of interannual variation in the density and growth rates of widely fluctuating populations of herbivorous small mammals.

Population dynamics of the rice root nematode Hirschmanniella oryzae on monsoon rice in Myanmar

Soil and root samples of the short crop cycle duration rice variety Yadanartoe were collected at 10-days intervals, starting at 20 days after transplanting until 20 days after harvest, from September 2008 until January 2009, to study the population dynamics of Hirschmanniella oryzae on (rainfed) monsoon rice. Plant growth stages, the ambient air and soil temperature, rainfall and relative humidity during the sampling period were noted. The soil type is clay and has a pH of 5.1. In the roots, three nematode population density peaks were observed during the sampling period: at the maximum tillering stage, at the milky grain stage, and between harvest and 10 days after harvest. The highest peak (483 H. oryzae/g roots) was observed at the milky grain stage. The lowest root population density (46 H. oryzae/g roots) was found at harvesting. Population densities in the soil followed more or less the same trend as in the roots. After harvesting, the soil population density increased. During our observation, we did not find any effects of environmental conditions on the population densities of H. oryzae. However, it was found that the population dynamics of H. oryzae were influenced by the plant growth stage.

A Mesocosm Study of the Changes in Marine Flagellate and Ciliate Communities in a Crude Oil Bioremediation Trial

Protozoan grazers play an important role in controlling the density of crude-oil degrading marine communities as has been evidenced in a number of microcosm experiments. However, small bioreactors contain a low initial titre of protozoa and the growth of hydrocarbon-depleting bacteria is accompanied by the fast depletion of mineral nutrients and oxygen, which makes microcosms rather unsuitable for simulating the sequence of events after the oil spill in natural seawater environment. In the present study, the population dynamics of marine protozoan community have been analysed in a 500 l mesocosm experiment involving bioaugmented oil booms that contained oil sorbents and slow-release fertilisers. A significant increase in numbers of marine flagellates and ciliates on biofilms of oil-degrading microbes was microscopically observed as early as 8 days after the start of the experiment, when protozoa exhibited a population density peak making up to 3,000 cells ml(-1). Further, the protozoan density varied throughout the experiment, but never dropped below 80 cells ml(-1). An 18S rRNA gene-based fingerprinting analysis revealed several changes within the eukaryotic community over the whole course of the experiment. Initial growth of flagellates and small ciliates was followed by a predominance of larger protozoa. According to microscopic observations and SSU rRNA molecular analyses, most predominant were the ciliates belonging to Euplotidae and Scuticociliatia. This is the first study to characterise the eukaryotic communities specifically in a large-scale oil bioremediation trial using both microscopy-based and several molecular techniques.

An examination of the population dynamics of syngnathid fishes within Tampa Bay, Florida, USA

Abstract Seagrass ecosystems worldwide have been declining, leading to a decrease in associated fish populations, especially those with low mobility such as syngnathids (pipefish and seahorses). This two-year pilot study investigated seasonal patterns in density, growth, site fidelity, and population dynamics of Tampa Bay (FL) syngnathid fishes at a site adjacent to two marinas under construction. Using a modified mark-recapture technique, fish were collected periodically from three closely located sites that varied in seagrass species (Thalassia spp., Syringodium spp., and mixed-grass sites) and their distance from open water, but had consistent physical/chemical environmental characteristics. Fish were marked, photographed for body size and gender measurements, and released the same day at the capture site. Of the 5695 individuals surveyed, 49 individuals were recaptured, indicating a large, flexible population. Population density peaks were observed in July of both years, with low densities in late winter and late summer. Spatially, syngnathid densities were highest closest to the mouth of the bay and lowest near the shoreline. Seven species of syngnathid fishes were observed, and species-specific patterns of seagrass use emerged during the study. However, only two species, Syngnathus scovelli and Hippocampus zosterae, were observed at high frequencies. For these two species, body size decreased across the study period, but while S. scovelli's population density decreased, H. zosterae's increased. Across six of the seven species, population size declined over the course of this preliminary study; however, seasonal shifts were impossible to distinguish from potential anthropogenic effects of construction.

Time Series Analysis Performed on Nephropathia Epidemica in Humans of Northern Sweden in Relation to Bank Vole Population Dynamic and the NAO Index

Time series analysis was performed on two data series of human nephropathia epidemica (NE) infections in northern Sweden between the years 1959-1975 and 1985-2006. The analysis confirms that the bank vole (Myodes glareolus), the main reservoir species, shows regular peaks in population density approximately every fourth year. The periodicity in NE cases of the more recent time period (1985-2006) is 2.8-3.3 years and the older period shows a periodicity ranging 3.4-4.2 years, but this is not significantly different from that expected by vole dynamics. A comparison of North Atlantic Oscillation (NAO) index between the two periods reveals higher mean winter NAO index in the period 1985-2006 than in 1959-1975. No difference was found in frequency of the NAO index between the older period (2.8-3.4 years) compared with the recent period (2.4-2.8 years). Cross-correlation revealed a delayed effect by NAO index on vole abundance but a multivariate model showed that NAO index did not explain the variation in NE cases. Vole index was the only factor that contributed significantly to the variation in numbers of NE cases and that no climate effect could be detected. The climate signal from NAO index does not appear to significantly affect the human NE cases and this suggests that the transmission of disease to man is not particularly sensitive to variations in weather factors. The results favour the hypothesis that higher NAO index will not increase the likelihood of virus transmission from voles to man in northern Sweden under present climatic conditions.

Does the Number of Diapausing Eggs Laid on Bark Affect the Population Dynamics of the Spider Mite Panonychus mori?

We studied the relationship between number of diapausing eggs produced by the spider mite Panonychus mori and the subsequent population trend for a period of 3 years. Panonychus mori showed a single population density peak on its host plant moonseed, Cocculus trilobus. The position and height of this peak were correlated with the density of diapausing eggs around the moonseed leaf buds produced the winter before. In 1994 the density of diapausing eggs measured in February was 4.3/bud, which was 6-14 times higher than the density of diapausing eggs for the same period in 1995 (0.3/bud) and 1996 (0.7/bud). The subsequent population density peak in 1994 occurred in mid June and was about 2.5 times higher than the peaks in 1995 and 1996, which both occurred early September. Thus, the present study showed a positive correlation between the density of diapausing eggs on the host plant and the start and the extend of the population increase the next growing season. Predators associated with the spider mite population were phytoseiid mites, especially Amblyseius eharai was well synchronized with the spider mite density in 1994. Field observations revealed that P. mori produced diapausing eggs in response to short photoperiod in early October each year, which corresponded with the timing predicted by the critical photoperiod around 13 h at 18 degrees C, as assessed in laboratory trials. Diapause ended by early April when egg hatchability attained about 50% and eggs took 9 days to hatch at 25 degrees C and a 16L:8D photoperiod. Hatching in early April was twice faster than in late February.

和歌山県のカキ園およびカンキツ園の雑草におけるミカンキイロアザミウマとネギアザミウマの発生消長

The western flower thrips, Flankliniella occidentalis (Pergande), and onion thrips, Thrips tabaci (Lindeman), cause serious damage to fruits of the ‘Tonewase’ persimmon when the fruit color turns yellow in early September. I investigated the seasonal abundance of the two thrips species on the various weed hosts in persimmon and mandarin orange orchards. Both F. occidentalis and T. tabaci overwintered on the biennial weeds such as chickweed, Lamium amplexicaule, and henbit, Stellaria neglecta. F. occidentalis showed two peaks in population density on weeds of orchards: one in May–June with the growth of biennial weeds and the other in July–August with the growth of annual weeds. Thus, the F. occidentalis population was shown to increase in association with the growth of wild plants. T. tabaci, on the other hand, had only one population peak in May, following the population continued to decrease toward the winter.

Factors affecting the occurrence of western flower thrips, Flankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) in persimmon orchards

Wakayama Prefecture is one of the main production areas of persimmon in Japan. However, western flower thrips, Flankliniella occidentalis (Pergande) has been causing serious damage to persimmon fruit, especially variety Tonewase, when the fruit color turned yellow in early September since 1997. F. occidentalis overwintered on the perennial weed such as chickweed, Stellaria neglecta, and had two peaks of population density on undergrowth of persimmon orchards: one in June when perennial weeds were growing and the other in July-August when summer weeds were growing. Thus F. occidentalis maintained its population through various undergrowth. Since the weeding time was different between persimmon and mandarin orange orchards, the adult F. occidentalis dispersed from an orchard where they existed at a higher density to the adjacent orchards. Therefore, the population density of F. occidentalis was higher in a persimmon-mandarin orange cultivation area than in a persimmon mono-cultivation area. The thrips density on undergrowth of foxtail ears, Setalia viridis, was higher in the persimmon orchard than in the grassland nearby. This is provably because pesticides applied to persimmon trees suppressed the occurrence of natural enemies such as the minute bug, Orius sauteri, on weeds by drafting, causing a resurgence of F. occidentalis in persimmon orchards.

Population Dynamics and Within-Plant Distribution of the Mite <I>Calacarus flagelliseta</I> (Acari: Eriophyidae) on Papaya in Hawaii

An important element in developing a management strategy for a new pest is the study of its seasonal dynamics and within-plant distribution. Here, we studied the mite Calacarus flagelliseta Fletchmann, De Moraes & Barbosa on papaya, Papaya carica L. (Caricaceae), in Hawaii to quantify 1) patterns of seasonal abundance, 2) its distribution across different vertical strata of the papaya canopy, and 3) shifts in its use of the upper versus the lower surfaces of papaya leaves. Nondestructive sampling conducted in two papaya plantings revealed that 1) populations of C. flagelliseta peak during the summer; 2) mites are most abundant in the middle and lower strata of the plant canopy, and least abundant on the youngest leaves found in the upper canopy; and 3) mites are found more predominantly on the upper leaf surfaces when overall population density peaks, suggesting that individuals move from the lower to the upper leaf surfaces when food resources on the lower leaf surface have been exploited by conspecifics. These results have significant implications for the development of sampling plans for C. flagelliseta in papaya.

Type 1 diabetes in Swedish bank voles (Clethrionomys glareolus): signs of disease in both colonized and wild cyclic populations at peak density.

Colonized bank voles (Clethrionomys glareolus) originating from Sweden developed type 1 diabetes. Animals became polydipsic, glucosuric, and hyperglycemic and gradually developed a lethal ketoacidosis. Pancreas in animals with end-stage disease showed total destruction of islet cells. Interestingly, also a high proportion of wild bank voles in cyclic populations that were trapped at (or close to) the cyclic population density peak frequently showed high blood glucose levels and pathological glucose tolerance test. Extensive islet destruction was not seen in wild bank voles at the time of capture, but did develop in some of the animals over a time period of two months. Diabetes in both colonized and wild bank voles was associated with Ljungan virus (LV). LV could be isolated from the pancreas of diabetic bank voles and antigen detected at the site of tissue damage by immunohistochemistry. In addition, picornavirus-like particles were visualized in the islets of diabetic voles using thin-section transmission electron microscopy.

Penilia avirostris (Crustacea, Ctenopoda) in a tropical bay: variations in density and aspects of reproduction

Populations of Penilia avirostris were studied in Guanabara Bay, southeastern Brazil, to assess temporal variations in the densities of parthenogenetic and gamogenetic individuals, length, and brood size. The abundance of P. avirostris varied widely during a brief 3-d period. These variations probably resulted from the combined action of water temperature, predation pressure by chaetognaths, and advection. Gamogenetic animals are found only during the peaks of population density of P. avirostris . To explain this phenomenon, we developed the hypothesis of constant population sex ratio : according to this hypothesis, the appearance of gamogenetic animals is a function, not of adverse environmental conditions, but rather of the low but constant rate of occurrence of males in the population.

Effects of extra food on population fluctuation patterns of the muroid rodent Calomys venustus

Abstract Population dynamics in the South American muroid rodent Calomys venustus are described from a 14‐year continuous data series, using the auto‐regressive integrated moving average (arima) model. Population responses to experimental food addition were analysed in two experimental areas, over two periods, using intervention analysis. There was no consistent evidence that food quantity leads to peaks in population density. Significant increases were related to densities of transients and juvenile individuals.

Spatial structure of lemming populations (Dicrostonyx groenlandicus) fluctuating in density.

The pattern and scale of the genetic structure of populations provides valuable information for the understanding of the spatial ecology of populations, including the spatial aspects of density fluctuations. In the present paper, the genetic structure of periodically fluctuating lemmings (Dicrostonyx groenlandicus) in the Canadian Arctic was analysed using mitochondrial DNA (mtDNA) control region sequences and four nuclear microsatellite loci. Low genetic variability was found in mtDNA, while microsatellite loci were highly variable in all localities, including localities on isolated small islands. For both genetic markers the genetic differentiation was clear among geographical regions but weaker among localities within regions. Such a pattern implies gene flow within regions. Based on theoretical calculations and population census data from a snap-trapping survey, we argue that the observed genetic variability on small islands and the low level of differentiation among these islands cannot be explained without invoking long distance dispersal of lemmings over the sea ice. Such dispersal is unlikely to occur only during population density peaks.

Seasonal dynamics of the population density of meiobenthos in Amurskii Bay, Sea of Japan

Seasonal dynamics of population densities and the qualitative composition of meiobenthos were studied in a strait between Popova and Reineke islands in Amurskii Bay (Sea of Japan). Two peaks of population density were revealed: a spring-summer peak and an autumn peak. No correlation was found between the depth, qualitative characteristics of the ground, and population density of meiobenthos.