scholarly journals Where Have All the Spiders Gone? Observations of a Dramatic Population Density Decline in the Once Very Abundant Garden Spider, Araneus diadematus (Araneae: Araneidae), in the Swiss Midland

Insects ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 248
Author(s):  
Martin Nyffeler ◽  
Dries Bonte
Keyword(s):  
Population Density ◽  
Trophic Cascade ◽  
Western Europe ◽  
Negative Impact ◽  
Normal Population ◽  
Late Summer ◽  
Population Fluctuations ◽  
Population Densities ◽  
Flying Insects ◽  
Araneus Diadematus

Aerial web-spinning spiders (including large orb-weavers), as a group, depend almost entirely on flying insects as a food source. The recent widespread loss of flying insects across large parts of western Europe, in terms of both diversity and biomass, can therefore be anticipated to have a drastic negative impact on the survival and abundance of this type of spider. To test the putative importance of such a hitherto neglected trophic cascade, a survey of population densities of the European garden spider Araneus diadematus—a large orb-weaving species—was conducted in the late summer of 2019 at twenty sites in the Swiss midland. The data from this survey were compared with published population densities for this species from the previous century. The study verified the above-mentioned hypothesis that this spider’s present-day overall mean population density has declined alarmingly to densities much lower than can be expected from normal population fluctuations (0.7% of the historical values). Review of other available records suggested that this pattern is widespread and not restricted to this region. In conclusion, the decline of this once so abundant spider in the Swiss midland is evidently revealing a bottom-up trophic cascade in response to the widespread loss of flying insect prey in recent decades.

scholarly journals Where have all the spiders gone? Observations of a dramatic population density decline in the once very abundant garden spider, Araneus diadematus (Araneae: Araneidae), in the Swiss midland

2020 ◽  
Author(s):  
Martin Nyffeler ◽  
Dries Bonte
Keyword(s):  
Population Density ◽  
Trophic Cascade ◽  
Western Europe ◽  
Negative Impact ◽  
Normal Population ◽  
Late Summer ◽  
Population Fluctuations ◽  
Population Densities ◽  
Flying Insects ◽  
Araneus Diadematus

AbstractAerial web-spinning spiders (including large orb-weavers) depend, as a group of insectivores, completely on flying insects as a food source. The recent widespread loss of flying insects across large parts of western Europe, both in terms of diversity and biomass, can therefore be anticipated to have a drastic negative impact on survival and abundance of this type of spiders. To test the putative importance of such a to date neglected trophic cascade, a survey of population densities of the European garden spider Araneus diadematus – a large orb-weaving spider – was conducted in late summer 2019 on twenty sites of the Swiss midland. The data from this survey were compared with published population densities for this species from the previous century. The study verifies above-mentioned hypothesis that this spider’s present-day overall mean population density has declined alarmly to densities much lower than can be expected from normal population fluctuations (0.7% of the historical densities). Review of other available records suggests this pattern is widespread and not restricted to this region. In conclusion, the here documented abundance decline of this once so abundant spider in the Swiss midland is evidently revealing a bottom-up trophic cascade in response to the widespread loss of flying insect prey in recent decades.

Effects of crop sequence and rainfall on population dynamics of Fusarium solani f.sp. phaseoli in soil

1992 ◽  
Vol 70 (10) ◽  
pp. 2005-2008 ◽  
Author(s):  
Robert Hall ◽  
Lana Gay Phillips
Keyword(s):  
Population Dynamics ◽  
Phaseolus Vulgaris ◽  
Population Density ◽  
Fusarium Solani ◽  
Population Densities ◽  
Total Rainfall ◽  
Colony Forming Units ◽  
Bean Crop ◽  
Previous Summer ◽  
Crop Sequence

Evidence is presented that population dynamics of Fusarium solani f.sp. phaseoli in soil depend on the effects of crop sequence and rainfall on parasitic activities of the pathogen. In a rotation trial started in 1978 and conducted over 14 years, population densities (colony-forming units/g) of the fungus in soil remained below 50 in treatments (fallow, repeated corn, repeated soybean) where the preferred host plant (common bean, Phaseolus vulgaris) was not grown. Where bean was grown every 3rd year or every year, population densities reached 475 and 660, respectively, by 1984. Thereafter, population densities of the fungus fluctuated widely from year to year in both rotation and repeated bean treatments. In the rotation treatment, peaks in population density of the pathogen coincided with the years of bean production. In repeated bean plots between 1985 and 1991, population density of the fungus in June was significantly correlated (r = 0.77, p = 0.04) with total rainfall received during the previous summer (June–August). It is postulated that higher rainfall during the growing season of the bean crop stimulated root growth and root infection, leading to the accumulation of higher levels of potential inoculum in infected tissue and the release of higher levels of inoculum into the soil by the following June. Key words: Fusarium solani f.sp. phaseoli, bean, Phaseolus vulgaris, rainfall, crop rotation.

Population Densities Allowed Around Dutch SEVESO Establishments

2000 ◽  
Author(s):  
G. M. H. Laheij ◽  
B. J. M. Ale ◽  
J. G. Post
Keyword(s):  
Population Density ◽  
The Netherlands ◽  
Individual Risk ◽  
Population Densities ◽  
Planning Policy ◽  
Relative Contribution ◽  
Societal Risk ◽  
Dangerous Substances ◽  
The Individual ◽  
Uniform Population

Abstract In the Netherlands, the individual risk and societal risk are used in efforts to reduce the number of people exposed to the effect of an accident at an establishment with dangerous substances. To facilitate the societal risk planning policy an investigation was carried out for the Dutch SEVESO establishments to investigate the possibility of determining a generic uniform population density for the zone between the individual risk contours of 10−5 and 10−6 per year. The indicative limit for the societal risk at this density was not to be exceeded. Also there was to be enough space left for a significantly higher population density outside the individual risk contour of 10−6 per year. The RORISC methodology and the actual data for the 124 Dutch SEVESO establishments were used to determine the generic uniform population density. Based on the data available it can be concluded that the maximum allowed uniform population density in the zone between the individual risk contours of 10−5 and 10−6 per year is lower than one person per hectare. At this density there is no space left for a higher population density outside the individual risk contour of 10−6 per year. For uniform population densities the relative contribution to the societal risk has been found significant up to the individual risk contour of 10−7 per year.

scholarly journals Effects of population density on cauliflower crop (Brassica oleracea L. var. botrytis)

1981 ◽  
Vol 38 (1) ◽  
pp. 1-10
Author(s):  
Keigo Minami ◽  
Ricardo Victoria Fº
Keyword(s):  
Population Density ◽  
Brassica Oleracea ◽  
Plant Population ◽  
Population Densities ◽  
Plant Population Density ◽  
Brassica Oleracea L ◽  
Quality Weight

An experiment was carried out to study the effects of the following population densities cauliflowers (plants per ha): 20,833 (0.60 m x 0.80 m), 25,641 (0.60 m x 0.65 m), ....37.037 (0.60 m x 0.45 m) , 55.555 (.0.60 m x 0.30 m), and 111,111 (0,60 m x 0,15 m) ; variety Snow ball. It was concluded that the effects of plant population density are greater on curd quality (weight and size) than on production per ha. The best plant population density to produce cauliflowers curd for Brazil market is from 20,000 to 25,000 plants/ha while for mini-curd is above 55,000 plants/ha.

Population dynamics and production of a brine shrimp, Parartemia zietziana Sayce (Crustacea : Anostraca), in two salt lakes in westren Victoria, Australia

1977 ◽  
Vol 28 (4) ◽  
pp. 417 ◽  
Author(s):  
R Marchant ◽  
WD Williams
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Temperature Stress ◽  
Brine Shrimp ◽  
Dry Weight ◽  
Salt Lakes ◽  
Confidence Limits ◽  
Length Frequency ◽  
Population Densities ◽  
The Mean

Quantitative samples of P. zietziana were taken monthly for two years from Pink Lake and Lake Cundare. Shrimps were usually contagiously distributed. To reduce error, samples were stratified resulting in confidence limits of 40-50% for the mean population density. Despite this variability, stable trends emerged, and variation was not so great as to mask significant differences. Length-frequency analyses distinguished cohorts; a regression was established between length and dry weight, enabling growth to be estimated from samples. By combining growth with population densities in Allen curves, production was computed. In Pink Lake and Lake Cundare mean pro- duction was 11.3 and 1.0 g dry weight m-2 year-1 respectively. Generally there were two or three generations per year, but time and extent of recruitment were not predictable. Each generation suffered continuous mortality, the death of young shrimps accounting for most of the production. This mortality remains unexplained; there are no significant predators and salinity and temperature stress would occur only during summer.

Macroinfauna of Northern New England marine sand. IV. Infaunal ecology of Amphiporeia virginiana Shoemaker, 1933 (Crustacea: Amphipoda)

1979 ◽  
Vol 57 (8) ◽  
pp. 1511-1519 ◽  
Author(s):  
Richard P. Hager ◽  
Robert A. Croker
Keyword(s):  
South Carolina ◽  
New England ◽  
Late Summer ◽  
Fine Sand ◽  
High Energy ◽  
Breeding Period ◽  
Population Fluctuations ◽  
Marine Sand ◽  
Annual Population ◽  
Early Fall

Amphiporeia virginiana occurs from Nova Scotia to South Carolina where it is a dominant inhabitant of high energy sand beaches. Maximum abundance occurs on the lower foreshore in fine sand particularly during summer months. Within-habitat segregation of sexes occurs, with females more abundant at higher beach levels; ovigerous females are confined to higher levels only. Annual population fluctuations of up to 14-fold on a geometric basis are related to life history events and sedimentary changes. Breeding occurs during most of the year with peak recruitment during June and late summer to early fall, yielding summer and overwintering generations. Precopulating animals are commonly seen swimming, with two males per female occasionally evident. Females produce a mean of 6–11 eggs during the year and have one brood per breeding period. The species is a detritivore and generally inhabits the upper 2.5 cm of sand. It is most tolerant of salinities in the range of 25–35‰; mortality increases rapidly in salinities less than 20‰, and in sediments containing less than 11% water by weight exposed to temperatures simulating hot summer days.

Grain Yield Gains and Associated Traits in Tropical X Temperate Maize Germplasm Under High and Low Plant Density

2021 ◽  
Author(s):  
Vince Ndou ◽  
Edmore Gasura ◽  
Pauline Chivenge ◽  
John Derera
Keyword(s):  
Population Density ◽  
Grain Yield ◽  
Plant Density ◽  
Plant Population ◽  
Population Densities ◽  
Genetic Gains ◽  
Maize Germplasm ◽  
High Plant Density ◽  
Number Of Leaves ◽  
Plant Population Density

Abstract Development of ideal breeding and crop management strategies that can improve maize grain yield under tropical environments is crucial. In the temperate regions, such yield improvements were achieved through use of genotypes that adapt high plant population density stress. However, tropical germplasm has poor tolerance to high plant population density stress, and thus it should be improved by temperate maize. The aim of this study was to estimate the genetic gains and identify traits associated with such gains in stable and high yielding temperate x tropical hybrids under low and high plant population densities. A total of 200 hybrids derived from a line x tester mating design of tropical x temperate germplasm were developed. These hybrids were evaluated for grain yield and allied traits under varied plant population densities. High yielding and stable hybrids, such as 15XH214, 15XH215 and 15XH121 were resistant to lodging and had higher number of leaves above the cob. The high genetic gains of 26% and desirable stress tolerance indices of these hybrids made them better performers over check hybrids under high plant population density. At high plant population density yield was correlated to stem lodging and number of leaves above the cob. Future gains in grain yield of these hybrids derived from temperate x tropical maize germplasm can be achieved by exploiting indirect selection for resistance to stem lodging and increased number of leaves above the cob under high plant density conditions.

Studies on the Ecology of the New Zealand Long-finned Eel, Anguilla dieffenbachii Gray

1952 ◽  
Vol 3 (1) ◽  
pp. 32 ◽  
Author(s):  
AMR Burnet
Keyword(s):  
New Zealand ◽  
Population Density ◽  
Mathematical Analysis ◽  
Feeding Habits ◽  
Stomach Contents ◽  
Limiting Factor ◽  
Population Densities ◽  
Baited Traps ◽  
Anguilla Dieffenbachii

Experimental trapping of eels, using carrion-baited traps, was carried out on a number of rivers of various types throughout New Zealand. Where possible, a mathematical analysis has been applied to the trapping results and an estimate of the efficiency obtained. Total trappable population densities of between 30 and 1,368 lb./ac. Were found. An attempt has been made to correlate type of river with the population density. The amount of cover present is apparently the limiting factor. The baited trap takes very few eels of less than 24 in. long and is thus not a very efficient means of keeping a stream free from eels. The feeding habits of the eel are generalized and readily adaptable to most faunas. In most rivers trout occurred only infrequently in the stomach contents.

scholarly journals Changes in Human Population Density and Protected Areas in Terrestrial Global Biodiversity Hotspots, 1995–2015

Land ◽  
2018 ◽  
Vol 7 (4) ◽  
pp. 136 ◽  
Author(s):  
Caitlin Cunningham ◽  
Karen Beazley
Keyword(s):  
Population Density ◽  
Protected Areas ◽  
Protected Area ◽  
Human Population ◽  
Area Coverage ◽  
Biodiversity Hotspots ◽  
Population Densities ◽  
Human Population Density ◽  
Global Average ◽  
Global Biodiversity

Biodiversity hotspots are rich in endemic species and threatened by anthropogenic influences and, thus, considered priorities for conservation. In this study, conservation achievements in 36 global biodiversity hotspots (25 identified in 1988, 10 added in 2011, and one in 2016) were evaluated in relation to changes in human population density and protected area coverage between 1995 and 2015. Population densities were compared against 1995 global averages, and percentages of protected area coverage were compared against area-based targets outlined in Aichi target 11 of the Convention on Biological Diversity (17% by 2020) and calls for half Earth (50%). The two factors (average population density and percent protected area coverage) for each hotspot were then plotted to evaluate relative levels of threat to biodiversity conservation. Average population densities in biodiversity hotspots increased by 36% over the 20-year period, and were double the global average. The protected area target of 17% is achieved in 19 of the 36 hotspots; the 17 hotspots where this target has not been met are economically disadvantaged areas as defined by Gross Domestic Product. In 2015, there are seven fewer hotspots (22 in 1995; 15 in 2015) in the highest threat category (i.e., population density exceeding global average, and protected area coverage less than 17%). In the lowest threat category (i.e., population density below the global average, and a protected area coverage of 17% or more), there are two additional hotspots in 2015 as compared to 1995, attributable to gains in protected area. Only two hotspots achieve a target of 50% protection. Although conservation progress has been made in most global biodiversity hotspots, additional efforts are needed to slow and/or reduce population density and achieve protected area targets. Such conservation efforts are likely to require more coordinated and collaborative initiatives, attention to biodiversity objectives beyond protected areas, and support from the global community.

The development of nursing care of the sick in Western Europe in the 18th and the first half of the 19th centuries

2019 ◽  
Vol 6 (1) ◽  
pp. 24-28
Author(s):  
Jerzy Supady
Keyword(s):  
19Th Century ◽  
French Revolution ◽  
Nursing Care ◽  
Western Europe ◽  
18Th Century ◽  
Negative Impact ◽  
Religious Congregations ◽  
The Right ◽  
Napoleon I ◽  
The 19Th Century

The Enlightenment ideology and the French Revolution had a very negative impact on the activities of religious congregations in respect of nursing care of the sick in hospitals in the 18th century. Emperor Napoleon I attempted to improve the existing situation by restoring the right for nursing care to nuns. In the first half of the 19th century, in Germany catholic religious orders had the obligation to provide nursing care and in the 30’s of the 19th century the Evangelical Church also joined charity work in hospitals by employing laywomen, i.e. deaconesses.

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