Food Limitation of Larval Dragonflies: A Field Test of Spacing Behaviour

1986 ◽  
Vol 43 (9) ◽  
pp. 1720-1725 ◽  
Author(s):  
Robert L. Baker
Keyword(s):  
Population Density ◽  
Field Test ◽  
Food Limitation ◽  
Population Densities ◽  
Larval Population ◽  
Southern Ontario ◽  
Growth And Survival ◽  
Gut Fullness ◽  
Dependent Growth ◽  
Ischnura Verticalis

Density-dependent growth and survival of larval odonates may result from some larvae excluding others from profitable hunting sites. This hypothesis predicts that both degree and variation in food limitation should increase with population density; it also suggests that large larvae should show less food limitation than small larvae. I tested these predictions by analyzing food limitation, determined by mass of fecal pellets, and population density of larval Ischnura verticalis and Enallagma ebrium from a pond in southern Ontario. When data from all sampling days were combined, population densities of both species were negatively correlated with gut fullness but there was no correspondence between population density and gut fullness measured at different sites on any given day. Also, there was no correlation between population density and variation in food limitation and there was no evidence that small larvae suffered a greater degree of food limitation than larger larvae. A lack of discrete and persistent prey patches and/or low larval population densities may account for the lack of evidence that larvae are excluded from patches of prey.

scholarly journals Browsing Patterns of White-Tailed Deer Following Increased Timber Harvest and a Decline in Population Density

2010 ◽  
Vol 2010 ◽  
pp. 1-7 ◽  
Author(s):  
Shawn M. Crimmins ◽  
John W. Edwards ◽  
W. Mark Ford ◽  
Patrick D. Keyser ◽  
James M. Crum
Keyword(s):  
Population Density ◽  
Odocoileus Virginianus ◽  
Population Control ◽  
Timber Harvest ◽  
Population Densities ◽  
Growth And Survival ◽  
Deer Population ◽  
Mature Forest ◽  
Central Appalachians ◽  
A Site

We examined browsing patterns of white-tailed deer (Odocoileus virginianus) on a site in the central Appalachians that experienced a substantial (>50%) reduction in deer population density and an increase in the amount of timber harvest since 2001. We sampled woody browse in and immediately adjacent to 12 clearcuts ranging in age from 0–5 years postharvest in summer 2007. Clearcut-interior areas had higher woody browse abundance and browsing rates than clearcut-edge or mature forest areas. Woody browse abundance was slightly higher within individual clearcuts than in 2001 at higher population densities and lower timber harvest rates. Overall browsing rates declined from approximately 17% in 2001 to less than 5% during our study, suggesting that the combination of deer population control, and increasing the amount of timber harvest across the landscape can reduce herbivory to levels that may not impede growth and survival of forest vegetation.

scholarly journals The Effects of Population Density on the Incidence of Developmental Deformities in Chemosensory Organs of Tobacco Hornworm Larvae (Lepidoptera: Sphingidae)

2020 ◽  
Vol 20 (4) ◽  
Author(s):  
Frank Hanson ◽  
Elizabeth Stanwyck ◽  
Alexander Bohorquez
Keyword(s):  
Life History ◽  
Population Density ◽  
Manduca Sexta ◽  
Life History Traits ◽  
Larval Density ◽  
Population Densities ◽  
Larval Population ◽  
Rate Of Development ◽  
Rearing Conditions ◽  
Chemosensory Organs

Abstract Cultures of Manduca sexta Johanssen in our laboratory were found to have larvae with missing or deformed mouthparts or antennae. Hypothesizing that these developmental deformities were caused by crowded rearing conditions, we reared larvae in four different population densities and recorded the incidence (% of larvae affected) and types of chemoreceptor deformities. Results showed that the incidence of these deformities was directly proportional to larval population density. Deformities of the maxilla and palp were the most frequent, followed by those of the antenna, epipharynx and maxillary styloconica. Life history traits of larval mass, food consumption, and rate of development were inversely related to larval density for both normal and deformed larvae. We discuss possible causes and mechanisms of these deformities and of changes to life history traits.

Expression of autogeny in relation to larval population density of Sarcophaga bullata Parker (Diptera: Sarcophagidae)

1973 ◽  
Vol 51 (11) ◽  
pp. 1189-1193 ◽  
Author(s):  
J. A. Baxter ◽  
A. M. Mjeni ◽  
P. E. Morrison
Keyword(s):  
Population Density ◽  
The Other ◽  
Larval Rearing ◽  
Population Densities ◽  
Larval Population ◽  
Sarcophaga Bullata ◽  
Other Hand ◽  
Rearing Conditions

The expression of autogeny in S. bullata was influenced by the larval rearing conditions. Low larval population densities resulted in large flies that were autogenous. On the other hand, high larval population densities produced small flies that were anautogenous, In anautogenous females the size and stage to which the follicles developed varied with the size of the fly. When reared on a sucrose–water diet, the females from an intermediate larval population density possessed larvae, mature eggs, degenerate follicles, or undeveloped follicles.

MONITORING SPRUCE BUDWORM POPULATION DENSITY WITH SEX PHEROMONE TRAPS

1988 ◽  
Vol 120 (2) ◽  
pp. 175-183 ◽  
Author(s):  
C.J. Sanders
Keyword(s):  
Sex Pheromone ◽  
Population Density ◽  
Choristoneura Fumiferana ◽  
Spruce Budworm ◽  
Pheromone Traps ◽  
Cooperative Research ◽  
Population Densities ◽  
Larval Population ◽  
Northwestern Ontario ◽  
Sex Pheromone Traps

AbstractAnnual catches of male spruce budworm (Choristoneura fumiferana [Clem.]) in sex pheromone traps over a 21-year period in northwestern Ontario were well correlated with larval population densities in each subsequent year (r2 = 81%). On the basis of the criterion of 3 successive years of increasing catches or a threshold of 50 moths per trap, warning of extensive defoliation could have been given 6 years in advance. In 18 plots in northwestern Ontario and 35 plots distributed throughout the province, coefficients of determination (r2) between catch and population density in the same generation ranged from 40 to 74% in 1982 and 1983, but fell below 23% in 1984 when population densities in many plots were high. Coefficients of determination between catch and population densities in the following generation (eggs or larvae) ranged from 41 to 62%. On the basis of several years of cooperative research, sex pheromone traps are now in operational use in eastern North America for monitoring spruce budworm populations.

scholarly journals THRESHOLD SIZE FOR FLOWERING IN DIFFERENT HABITATS: EFFECTS OF SIZE-DEPENDENT GROWTH AND SURVIVAL

Ecology ◽  
1997 ◽  
Vol 78 (7) ◽  
pp. 2118-2132 ◽  
Author(s):  
Renate A. Wesselingh ◽  
Peter G. L. Klinkhamer ◽  
Tom J. de Jong ◽  
Laurence A. Boorman
Keyword(s):  
Growth And Survival ◽  
Threshold Size ◽  
Size Dependent ◽  
Dependent Growth

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.

Sign in / Sign up

Export Citation Format

Share Document