Population Increase (population + increase)

Distribution by Scientific Domains
Distribution within Life Sciences


Selected Abstracts


Preference and performance of the hyperparasitoid Syrphophagus aphidivorus (Hymenoptera: Encyrtidae): fitness consequences of selecting hosts in live aphids or aphid mummies

ECOLOGICAL ENTOMOLOGY, Issue 6 2004
R. Buitenhuis
Abstract., 1.,Theoretical models predict that ovipositional decisions of parasitoid females should lead to the selection of the most profitable host for parasitoid development. Most parasitoid species have evolved specific adaptations to exploit a single host stage. However, females of the aphid hyperparasitoid Syrphophagous aphidivorus (Mayr) (Hymenoptera: Encyrtidae) display a unique and atypical oviposition behaviour by attacking either primary parasitoid larvae in live aphids, or parasitoid pupae in dead, mummified aphids. 2.,In the laboratory, the correlation between host suitability and host preference of S. aphidivorus on the host Aphidius nigripes Ashmead parasitising the aphid Macrosiphum euphorbiae (Thomas) was investigated. 3.,The relative suitability of the two host stages was determined by measuring hyperparasitoid fitness parameters (survival, development time, fecundity, sex ratio, and adult size of progeny), and calculating the intrinsic rate of population increase (rm). Host preference by S. aphidivorus females and the influence of aphid defence behaviour on host selection was also examined. 4.,Hyperparasitoid offspring performance was highest when developing from hosts in aphid mummies and females consistently preferred this host to hosts in parasitised aphids. Although aphid defensive behaviour may influence host selection, it was not a determining factor. Ecological and evolutionary processes that might have led to dual oviposition behaviour in S. aphidivorus are discussed. [source]


The significance of a facultative bacterium to natural populations of the pea aphid Acyrthosiphon pisum

ECOLOGICAL ENTOMOLOGY, Issue 2 2003
A. C. Darby
Abstract. 1., Laboratory studies have implicated various accessory bacteria of aphids as important determinants of aphid performance, especially on certain plant species and under certain thermal regimes. One of these accessory bacteria is PABS (also known as T-type), which is distributed widely but is not universal in natural populations of the pea aphid Acyrthosiphon pisum in the U.K. 2., To explore the impact of PABS on the performance of A. pisum , the nymphal development time and fecundity of aphids collected directly from natural populations and caged on the host plant Vicia faba in the field were quantified. Over 4 consecutive months June,September 1999, the performance of PABS-positive and PABS-negative aphids did not differ significantly. 3., Deterministic modelling of the performance data showed that the variation in simulated population increase of PABS-positive and PABS-negative aphids would overlap substantially. 4., Analysis of aphids colonising five host plants ( Lathyrus odoratus , Medicago sativa , Pisum sativum , Trifolium pratense , Vicia faba ) between April and September 2000 and 2001, identified no robust differences between the distribution of PABS-positive and PABS-negative aphids on different plants and with season or temperature. 5., It is concluded that PABS is not an important factor shaping the performance or plant range of A. pisum under the field conditions tested. Reasons for the discrepancies between this study and laboratory-based studies are considered. [source]


Disease burden of chronic lymphocytic leukaemia within the European Union

EUROPEAN JOURNAL OF HAEMATOLOGY, Issue 4 2008
Louise Watson
Abstract Objective:, Whilst Chronic lymphocytic leukaemia (CLL) is considered a rare disease, to our knowledge, the current prevalence of CLL within the European Union (EU) member states is not published. Understanding the number of individuals with CLL is vital to assess disease burden within the wider population. Methods:, Using 2002 data from the International Agency for Research on Cancer, we estimated the number of individuals with CLL (ICD-10 C91.1) from those reported for all leukaemias (C91,95) and extrapolated the figures by the population increase within the EU between 2002 and 2006, the last year with fully updated community population estimates. One- and 5-yr partial prevalence estimates are reported (i.e. the number of individuals still living 1,5 yr post-diagnosis). We then applied proportional estimates from the literature to assess those requiring immediate treatment, those under observation and their likely progression rates. Results:, We found that within the 27 EU states plus Iceland, Norway and Lichtenstein, 1- and 5-yr CLL partial prevalence estimates totalled approximately 13 952 and 46 633 individuals respectively in 2006. By applying Binet staging to the 1-yr estimate, 40% of patients will be stage B/C and require immediate treatment. Thus, 5581 individuals may be treated within the first year of diagnosis. Of the 60% (8371) under observation, by 5 yr up to 33% (2763) may have more advanced disease with increased risk of mortality. Conclusion:, Whilst CLL is a rare disease, the number of individuals burdened by the disease within the EU is considerable and thousands of patients require treatment and physician care, which has cost implications for member states. [source]


Pressure plate studies to determine how moisture affects access of bacterial-feeding nematodes to food in soil

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2002
G.W. Yeates
Summary Nematode activity in the soil depends on the presence of free water. We conducted pressure plate experiments to understand better how soil matric potential and structural degradation affect the population growth of three bacterial-feeding nematodes (Cephalobus, Pristionchus, Rhabditis). We took undisturbed cores from six soils (sand, silt loam and silty clay loam with four management regimes), and removed all fauna from them. Ten or 30 nematodes were added, and pressures corresponding to soil matric potentials of ,10, ,33, ,50, ,100 or ,1500 kPa were applied for 35 days. The nematodes were then counted. Significant reproduction of all bacterial-feeding nematodes occurred when the diameters of water-filled pores were approximately 1 ,m. This confirms observations using repacked soils and field manipulations. Only for Pristionchus did declining populations match the reduction in total soil porosity related to intensification of land use on the silty clay loam. We had not expected Cephalobus to have the fastest increase in population of the three nematodes in intact soil cores, and our evidence questions the relative importance given to the three nematode families in soil processes. The differing rates of population increase of the three nematodes in the various soils reflect both habitable pore space and trophic interactions. This suggests that the very diversity of nematode assemblages is crucial in the resilience of biological soil processes. That water-filled pores as small as 1 ,m provide suitable spaces for sizeable populations of bacterial-feeding nematodes accords with the observed migration of infective juveniles of trichostrongylid nematodes and mermithids in water films on herbage. Our results imply that assessment of the role of nematodes in soil processes may be a key to the understanding of biological interactions in water films, and the selection pressures on nematode morphology. [source]


PLASTICITY IN QUEEN NUMBER AND SOCIAL STRUCTURE IN THE INVASIVE ARGENTINE ANT (LINEPITHEMA HUMILE)

EVOLUTION, Issue 10 2002
Krista K. Ingram
Abstract., In many polygynous social insect societies, ecological factors such as habitat saturation promote high queen numbers by increasing the cost of solitary breeding. If polygyny is associated with constrained environments, queen number in colonies of invasive social insects should increase as saturation of their new habitat increases. Here I describe the variation in queen number, nestmate relatedness, and nest size along a gradient of time since colonization in an invading population of Argentine ants (Linepithema humile) in Haleakala, Hawaii. Nest densities in this population increase with distance from the leading edge of the invasion, reaching a stable density plateau approximately 80 m from the edge (> 2 years after colonization). Although the number of queens per nest in Haleakala is generally lower than previously reported for Argentine ants, there is significant variation in queen number across this population. Both the observed and effective queen numbers increase across the density gradient, and nests in the center of the population contain queen numbers three to nine times higher than those on the edge of the invasion. The number of workers per nest is correlated with queen number, and nests in the center are six times larger than nests at the edge. Microsatellite analysis of relatedness among nestmates reveals that all nests in the Haleakala population are characterized by low relatedness and have evidence of multiple reproducing queens. Relatedness values are significantly lower in nests in the center of the population, indicating that the number of reproducing queens is greater in areas of high nest density. The variation in queen number and nestmate relatedness in this study is consistent with expectations based on changes in ecological constraints during the invasion of a new habitat, suggesting that the social structure of Argentine ant populations is strongly influenced by ecological factors. Flexibility in social structure may facilitate persistence in variable environments and may also confer significant advantages to a species when introduced into new areas. [source]


Interactions between land use, habitat use, and population increase in greater snow geese: what are the consequences for natural wetlands?

GLOBAL CHANGE BIOLOGY, Issue 6 2005
Gilles Gauthier
Abstract The North American greater snow goose population has increased dramatically during the last 40 years. We evaluated whether refuge creation, changes in land use on the wintering and staging grounds, and climate warming have contributed to this expansion by affecting the distribution, habitat use, body condition, and migration phenology of birds. We also reviewed the effects of the increasing population on marshes on the wintering grounds, along the migratory routes and on the tundra in summer. Refuges established before 1970 may have contributed to the initial demographic increase. The most important change, however, was the switch from a diet entirely based on marsh plants in spring and winter (rhizomes of Scirpus/Spartina) to one dominated by crops (corn/young grass shoots) during the 1970s and 1980s. Geese now winter further north along the US Atlantic coast, leading to reduced hunting mortality. Their migratory routes now include portions of southwestern Québec where corn production has increased exponentially. Since the mid-1960s, average temperatures have increased by 1,2.4°C throughout the geographic range of geese, which may have contributed to the northward shift in wintering range and an earlier migration in spring. Access to spilled corn in spring improved fat reserves upon departure for the Arctic and may have contributed to a high fecundity. The population increase has led to intense grazing of natural wetlands used by geese although these habitats are still largely undamaged. The foraging in fields allowed the population to exceed limits imposed by natural marshes in winter and spring, but also prevented permanent damage because of their overgrazing. [source]


Breeding performance, age effects and territory occupancy in a Bonelli's Eagle Hieraaetus fasciatus population

IBIS, Issue 2 2008
JOSÉ A. MARTÍNEZ
Bonelli's Eagle Hieraaetus fasciatus is one of the most endangered birds of prey in Europe. Despite mounting interest and research, several questions regarding the conservation implications of territory occupancy and site-dependent population regulation remain insufficiently explored for this species. Here, we report on a 12-year study of the territorial structure of a Bonelli's Eagle population in southeastern Spain. No signals of population decline were found in the breeding population, as mean annual productivity was stable and the presence of mixed-age pairs in the population decreased with the years. However, the average proportion of subadults occupying territories was larger than that observed in other Spanish populations. Contrary to the predictions of a despotic distribution model, we found no significant relationship between occupancy rates and breeding parameters. Our results showed significant variations in productivity attributable to differences in the quality of individuals (i.e. mixed versus adult pairs), but no variability among territories per se (i.e. caused by habitat heterogeneity). Moreover, coexistence with intraguild species did not have any significant effect on productivity, although the proximity of Eagle Owls Bubo bubo affected the occupation rate of territories. Finally, our population does not appear to experience site-dependent population regulation, as a positive relation between mean annual productivity and density was found. The threat posed by changes in land use in the study area leads us to suggest that strict protection of current territories is necessary to ensure population persistence, and we suggest that a significant population increase is only likely if new or deserted territories become available. [source]


Predicting the population consequences of human disturbance for Ringed Plovers Charadrius hiaticula: a game theory approach

IBIS, Issue 2007
DURWYN LILEY
Human disturbance and its potential impacts upon bird populations are currently topical and contentious issues for conservationists. Although many studies have revealed a behavioural impact, or even direct effect on breeding success or survival, these cannot usually be extended to predict the impact on population size. Here we present a population model that allows predictions of the effect that changes in human numbers, visiting a 9-km-long section of the coastline, may have upon the size of a Ringed Plover Charadrius hiaticula population. Human disturbance affects Ringed Plovers in our study area through birds avoiding areas of high disturbance and, in addition, through the accidental trampling of a small number of nests by people walking on the beach. Using the level of human disturbance and habitat variables (which define territory quality) it is possible to predict which areas of beach are occupied and therefore the sites available to the population. Breeding success, for a given area of beach, can be predicted from habitat data. Incorporating known, density-independent, adult mortality allows the equilibrium population size to be predicted. This provides a model that predicts population size. This model is then used to predict the population that the site would support with different, hypothetical, levels of disturbance. If nest loss from human activity was prevented, for example by fencing nests, we predict the Plover population size would increase by 8%. A complete absence of human disturbance would cause a population increase of 85%. If the numbers of people were to double, we predict the population would decrease by 23%. [source]


Non-independence of demographic parameters: positive density-dependent fecundity in eagles

JOURNAL OF APPLIED ECOLOGY, Issue 5 2008
Miguel Ferrer
Summary 1Using information on the Doñana population of Spanish imperial eagles Aquila adalberti from 1959 to 2004, we present strong empirical support to theoretical models on the regulation of population trajectories by the relationships between breeder mortality and floater availability. 2During the study period, the eagle population showed three distinct phases: (i) a population increase with negative density-dependent fecundity; (ii) a period of stability without any relationship between density and fecundity; and (iii) a population decrease with a positive relationship between density and fecundity. 3A dramatic increase in annual adult mortality due to an increase in poisoning in hunting areas surrounding the Doñana National Park was recorded. The use of poison against generalist predators accounted for more than 54% of the total number of breeding eagles found dead since 1990, increasing annual adult mortality from 6·07 to 12·01%. 4This high mortality reduced the population annually by 6% during the 1992,2004 period. Also, the population changed from a negative to a positive relationship between density and fecundity (Allee effect). These trends made the population approach extinction due to the double effect of increasing breeder mortality and low availability of floaters. 5A supplementary feeding programme established in 1990 did not increase fecundity because it was a consequence of high adult mortality rather than low food availability. The high mortality of adults increased the risk of breeding failure and also decreased the availability of floaters, decreasing the likelihood of mate substitution. 6Synthesis and applications. The main target in species conservation management plans is often a single demographic parameter (typically, fecundity in raptor populations). Our research demonstrates, however, that demographic parameters must not be considered as independent variables when formulating management programmes. The essential relationship between adult mortality and the availability of floaters must be better understood to avoid the risk of implementing inefficient management strategies. Although fecundity was low in this eagle population, it was a result of high adult mortality rates. Consequently, management must aim to correct the unusual mortality and recover the floater population. [source]


Constructing life-tables for the invasive maize pest Diabrotica virgifera virgifera (Col.; Chrysomelidae) in Europe

JOURNAL OF APPLIED ENTOMOLOGY, Issue 4 2006
S. Toepfer
Abstract:, The western corn rootworm (Diabrotica virgifera virgifera LeConte, Col.; Chrysomelidae) is an alien invasive species in Europe. It is a univoltine species with eggs that overwinter in the soil and larvae that hatch in spring. Three larval instars feed on maize roots, which can cause plant lodging and yield loss of economic importance. Adults emerge between mid-June and early August and can reduce yields through intensive silk feeding. In order to provide a thorough understanding of the population dynamics of this invasive pest species in the invaded European region, complete age specific life-tables were constructed in two maize fields in southern Hungary assessing the significance of natural mortality factors acting on D. v. virgifera populations. This information provides a rational basis for devising sustainable integrated pest management programmes, in particular, by enabling the identification of vulnerable pest age intervals for the timely application of various management tools. The life-table for D. v. virgifera in Europe resulted in a total mortality of about 99% from the egg stage in the autumn to the emergence of adult females in the following year (KTotal = 2.48), which is comparable with North America. The highest reduction of D. v. virgifera numbers resulted from the mortality in first instar larvae (94% marginal death rate) and from the unrealized fecundity (80%). However, only the variation in mortality between years can change the generational mortality and thus influence population growth. High variation in the marginal death rate between fields and years was found in the second and third instar larval stages, and in the overwintering egg stage. These mortality factors therefore have the potential to cause changes in the total generational mortality. Furthermore, the life-table suggested that a high fecundity could compensate for a high generational mortality and would lead to population increase. [source]


Effect of eggplant transformed with oryzacystatin gene on Myzus persicae and Macrosiphum euphorbiae

JOURNAL OF APPLIED ENTOMOLOGY, Issue 2 2006
A. P. O. Ribeiro
Abstract:, The effect of a genetically modified eggplant line expressing oryzacystatin on Myzus persicae (Sulzer) and Macrosiphum euphorbiae (Thomas) was examined. The transgenic eggplant reduced the net reproductive rate (R0), the instantaneous rate of population increase (r), and the finite rate of population increase (,) of both aphids species compared with a control eggplant line. The mean generation time (T) of the aphids was unaffected by the transgenic plants. Age-specific mortality rates of M. persicae and M. euphorbiae were higher on transgenic plants. These results indicate that expression of oryzacystatin in eggplant has a negative impact on population growth and mortality rates of M. persicae and M. euphorbiae and could be a source of plant resistance for pest management of these aphids. [source]


ORIGINAL ARTICLE: Towards an understanding of the Holocene distribution of Fagus sylvatica L.

JOURNAL OF BIOGEOGRAPHY, Issue 1 2007
Thomas Giesecke
Abstract Aim, Understanding the driving forces and mechanisms of changes in past plant distribution and abundance will help assess the biological consequences of future climate change scenarios. The aim of this paper is to investigate whether modelled patterns of climate parameters 6000 years ago can account for the European distribution of Fagus sylvatica at that time. Consideration is also given to the role of non-climatic parameters as driving forces of the Holocene spread and population expansion of F. sylvatica. Location, Europe. Methods, European distributions were simulated using a physiologically-based bioclimatic model (STASH) driven by three different atmospheric general circulation model (AGCM) outputs for 6000 years ago. Results, The three simulations generally showed F. sylvatica to have potentially been as widespread 6000 years ago as it is today, which gives a profound mismatch with pollen-based reconstructions of the F. sylvatica distribution at that time. The results indicate that drier conditions during the growing season 6000 years ago could have caused a restriction of the range in the south. Poorer growth conditions with consequently reduced competitive ability were modelled for large parts of France. Main conclusions, Consideration of the entire European range of F. sylvatica showed that no single driving force could account for the observed distributional limits 6000 years ago, or the pattern of spread during the Holocene. Climatic factors, particularly drought during the growing season, are the likely major determinants of the potential range. Climatic factors are regionally moderated by competition, disturbance effects and the intrinsically slow rate of population increase of F. sylvatica. Dynamic vegetation modelling is needed to account for potentially important competitive interactions and their relationship with changing climate. We identify uncertainties in the climate and pollen data, as well as the bioclimatic model, which suggest that the current study does not identify whether or not climate determined the distribution of F. sylvatica 6000 years ago. Pollen data are better suited for comparison with relative abundance gradients rather than absolute distributional limits. These uncertainties from a study of the past, where we have information about plant distribution and abundance, argue for extreme caution in making forecasts for the future using equilibrium models. [source]


Rarity, specialization and extinction in primates

JOURNAL OF BIOGEOGRAPHY, Issue 4 2002
A. H. Harcourt
Aim To determine and explain biological traits that distinguish rare from common primate taxa. Location Africa, Americas, Asia, Madagascar. Methods We compare the biology of rare primate taxa with the biology of common taxa. Rarity is defined by (1) small size of geographic range; (2) small geographic range plus low local population density; and (3) small geographic range plus low local density plus narrow habitat specificity. After a linear comparison of size of geographic range with various biological traits, globally and by realm, extremes of rarity and commonness per realm are identified, and then combined for a global analysis. Tests are done both with genera treated as independent data points (n=62), and also with phylogenetic control by use of an independent contrasts test. Extinction risk in vertebrates, including primates, often correlates with high resource requirements, slow population recovery rate, and specialization. The three indices of rarity are therefore compared with these three general traits. Measures of resource use are body mass, local density, annual range size, and group size; of recovery rate, interbirth interval, and maximum intrinsic rate of natural population increase; and of degree of specialization, variety of diet, of habitats, maximum latitude, and morphological variety. All data come from the literature. Because several measures are compared, probabilities are Bonferroni corrected. Results If rarity in primates correlates with any biological attribute, it consistently correlates with only measures of specialization, and not with measures of high resource use, or slow population recovery rate. Without phylogenetic correction, the first two indices of rarity associate significantly with all four measures of specialization, and the third with maximum latitude. With phylogenetic correction, the first index still associates with all four, the second with two (maximum latitude, number of species per genus), and the third shows no significant associations. While the four measures of specialization are strongly interrelated, stepwise regressions on geographic range indicate that maximum latitude has the strongest effect, followed by dietary variety and number of species per genus and, finally, habitat variety. Main conclusions The most commonly demonstrated traits of susceptibility to extinction are those of high resource use, slow recovery rate, and specialization. Yet, while rarity (almost however, it is defined) is an inevitable precursor to extinction, specialization is the only trait found to correlate with rarity in this study. We cannot explain this apparent contradiction. [source]


Escape in space from enemies: a comparison between stands with and without enhanced densities of the spruce bark beetle

AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 2 2007
Leif Martin Schroeder
Abstract 1,Populations of the spruce bark beetle, Ips typographus (L.), are known to grow rapidly in storm-disturbed stands as a result of relaxation from intraspecific competition. In the present study, it was tested whether a second mechanism, escape in space from natural enemies, also contributes to the rapid population increase. 2,The experiment was conducted during the initiation phase of five local outbreaks of I. typographus triggered by a storm-disturbance in November 1995 in southern Sweden. 3,The impact of natural enemies on the ratio of increase (number of daughters per mother) of I. typographus was compared pairwise between disturbed stands with high numbers of storm-felled trees and undisturbed stands without wind-felled trees. 4,Enemy impact was assessed by comparing the ratio of increase in uncaged (exposed to enemies) and caged (protected from enemies) bolts colonized by I. typographus prior to being placed in the stands. The experiment was conducted in the second and third summers after the storm-felling. 5,Enemy impact was about twice as high in stands without wind-felled trees compared with in stands with wind-felled trees in the second summer whereas there was no significant difference between the stand types in the third summer. 6,The result demonstrates that spatial escape from enemies contributes to the rapid population growth of I. typographus after storm-disturbances. [source]


CAUSES OF MORTALITY IN CALIFORNIA SEA OTTERS DURING PERIODS OF POPULATION GROWTH AND DECLINE

MARINE MAMMAL SCIENCE, Issue 1 2003
JamesA.
Abstract Elevated mortality appears to be the main reason for both sluggish growth and periods of decline in the threatened California sea otter population. We assessed causes of mortality from salvage records of 3,105 beach-cast carcasses recovered from 1968 through 1999, contrasting two periods of growth with two periods of decline. Overall, an estimated 40%-60% of the deaths were not recovered and 70% of the recovered carcasses died from unknown causes. Nonetheless, several common patterns were evident in the salvage records during the periods of population decline. These included greater percentages of (1) prime age animals (3,10 yr), (2) carcasses killed by great white shark attacks, (3) carcasses recovered in spring and summer, and (4) carcasses for which the cause of death was unknown. Neither sex composition nor the proportion of carcasses dying of infectious disease varied consistently between periods of population increase and decline. The population decline from 1976 to 1984 was likely due to incidental mortality in a set-net fishery, and the decline from 1995 to 1999 may be related to a developing live-fish fishery. Long-term trends unrelated to periods of growth and decline included a decrease in per capita pup production and mass/length ratios of adult carcasses over the 31-yr study. The generally high proportion of deaths from infectious disease suggests that this factor has contributed to the chronically sluggish growth rate of the California sea otter population. [source]


Lifetime reproductive output of Calliphora vicina and Lucilia sericata in outdoor caged and field populations; flight vs. egg production?

MEDICAL AND VETERINARY ENTOMOLOGY, Issue 4 2006
LEWIS DAVIES
Abstract Females of the blowflies Calliphora vicina (Robineau-Desvoidy) and Lucilia sericata (Meigen) (Diptera: Calliphoridae) maintained in sheltered outdoor cages and supplied with excess food, oviposited later than would have been expected from the temperature-sum. The survival rates of the caged flies was high and the isolation of flies from predation, extreme temperatures and food shortages is likely to have contributed to this. Despite good survival rates, subsequent egg production over the greater part of the adult life span was reduced to ,24% for C. vicina and ,55% for L. sericata, of the potential expected from the published temperature-sums required for the maturation of successive egg batches. The data suggest that under field-cage conditions there is a considerable variation in egg development between individuals of the same age and that this variation should not be overlooked, since it may have significant implications in ecological and forensic investigations; however, the cause of this variability remains unclear. While lower than expected, the reproductive outputs recorded in the cages were nevertheless considerably greater than those that have been estimated for blowflies in the field and illustrate the potential for population increase in these species under favourable conditions. The possibility of a greater energy investment in flight activity relative to reproductive output in C. vicina compared to L. sericata is proposed. [source]


Paradoxical effects of sublethal exposure to the naturally derived insecticide spinosad in the dengue vector mosquito, Aedes aegypti

PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 3 2009
Gloria E Antonio
Abstract BACKGROUND: Recent studies have indicated that spinosad, a mixture of two tetracyclic macrolide compounds produced during the fermentation of a soil actinomycete, may be suitable for controlling a number of medically important mosquito species, including the dengue vector, Aedes aegypti L. The authors determined the effects of a 1 h exposure to a 50% lethal concentration (LC50) of spinosad in the larval stage on the wing length, longevity and reproductive capacity of the adult survivors. RESULTS: The LC50 of spinosad for a wild-caught population of Ae. aegypti from Chiapas, southern Mexico, was estimated to be 0.06 mg AI L,1 in late third instars. Paradoxically, the female survivors of exposure to this concentration were significantly larger (as determined by wing length) laid more eggs, but were slightly less fertile than control females. This was probably due to elimination of the smaller and more susceptible fraction of mosquito larvae from the experimental population following spinosad treatment. Male survivors, in contrast, were significantly smaller than controls. No significant differences were detected in the adult longevity of treated and control insects of either sex. CONCLUSIONS: The increase in reproductive capacity of spinosad-treated females did not compensate for mortality in the larval stage and would be unlikely to result in population increase in this mosquito under the conditions that were employed. Sustained-release formulations would likely assist in minimizing the occurrence of sublethal concentrations of this naturally derived product in mosquito breeding sites. Copyright © 2008 Society of Chemical Industry [source]


On Integrating Immigrants in Germany

POPULATION AND DEVELOPMENT REVIEW, Issue 3 2006
Article first published online: 8 SEP 200
Immigration to Germany in the decades following World War II made the Federal Republic the host of the largest number of immigrants in Europe. The size of the population with an immigration background is on the order of 15 million, nearly one-fifth of the total population. (Many of these are ethnic German returnees.) Although restrictive policies and a less dynamic economy in recent years slowed the annual number of immigrants and asylum seekers, the interrelated demographic influences of very low fertility, negative natural population increase, and population aging make continuing future immigration likely and, judged by influential domestic interests, desirable. Anxieties about inadequate integration of immigrants in German society are, however, apparently strongly felt by large segments of the native population. The "Grand Coalition" government that took office in November 2005 considers the formation of an effective policy of integration a high priority. On 14 July 2006 an "Integration Summit" was convened in the Chancellery with the active participation of representatives of immigrant groups. Chancellor Angela Merkel called the Summit "an almost historical event." Reproduced below in full is a non-official English translation of a government statement (entitled "Good coexistence,Clear rules") presented to the participants at the opening of the meeting. Intended as a "start of the development of a national integration plan," the statement highlights existing deficiencies of integration, especially problems with second- and third-generation immigrants: lack of mastery of the German language, weaknesses in education and training, high unemployment, lack of acceptance of the basic rules of coexistence, and violation of the law. The importance of these issues is underlined by a demographic fact noted in the statement: by 2010 it is expected that in Germany's large cities 50 percent of the population under age 40 will have an immigrant background. The statement recognizes the government's responsibility to help immigrants learn German and become better informed about the country's laws, culture, history, and political system. In turn, it demands reciprocal efforts from migrants living permanently and lawfully in Germany. The original German text of the statement is available at the Bundeskanzleramt home page: «http://www.bundesregierung.d» [source]


Bridewealth and Birth Control: Low Fertility in the Indonesian Archipelago, 1500,1900

POPULATION AND DEVELOPMENT REVIEW, Issue 2 2003
Peter Boomgaard
Before the onset of the present demographic transition, population growth in Indonesia had reached unprecedentedly high levels. This article demonstrates that such high levels were a recent phenomenon. Prior to 1900 rates of natural population increase were low to very low in most areas in Indonesia. This runs counter to expectations based on Hajnal's "Eastern marriage pattern," which could imply high growth levels in extended family areas, such as most Indonesian regions outside Java in the past. Usually, the low population growth rates in Southeast Asia are attributed to high mortality owing to high levels of violent conflict. It is argued that other factors contributing to such high levels of mortality should receive more attention. In this article it is also argued that low fertility rates, too, played a role in generating low rates of natural increase. The article discusses the influence of marriage patterns, household structure, methods of birth control, adoption, and slavery on fertility. [source]


Differential indirect effects of two plant viruses on an invasive and an indigenous whitefly vector: implications for competitive displacement

ANNALS OF APPLIED BIOLOGY, Issue 3 2009
J. Liu
Abstract The role of vector,begomovirus,plant interactions in the widespread invasion by some members of the whitefly species complex Bemisia tabaci is poorly understood. The invasive B biotype of B. tabaci entered China in the late 1990s and had become the predominant or only biotype of the whitefly in many regions of the country by 2005,2006. Meanwhile epidemics of begomoviruses have been observed in many crops including tomato for which Tomato yellow leaf curl China virus (TYLCCNV) and Tomato yellow leaf curl virus (TYLCV) have been identified as two major disease-causing agents. Here, we conducted laboratory experiments to compare the performance of the invasive B and indigenous ZHJ1 whitefly biotypes on uninfected, TYLCCNV-infected and TYLCV-infected plants of tomato cv. Hezuo903, a cultivar that has been widely cultivated in many regions of China. The infection of tomato plants by either of the viruses had no or only marginal effects on the development, survival and fecundity of the B biotype. In contrast, survival and fecundity of the ZHJ1 biotype were significantly reduced on virus-infected plants compared to those on uninfected plants. Populations of the B biotype on uninfected and TYLCCNV-infected plants increased at similar rates, whereas population increase of the ZHJ1 biotype on TYLCCNV-infected plants was affected adversely. These asymmetric responses to virus infection of tomato plants between the B and ZHJ1 biotypes are likely to offer advantages to the B biotype in its invasion and displacement of the indigenous biotype. [source]


Spatially explicit trophic modelling of a harvested benthic ecosystem in Tongoy Bay (central northern Chile)

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 6 2002
Marco Ortiz
Abstract 1.A dynamical and spatial simulation model of a harvested benthic ecosystem of central northern Chile (Tongoy Bay) was constructed using the ECOSPACE software package. 2.In this system the red alga (Chondrocanthus chamissoi), the scallop (Argopecten pupuratus), the gastropod (Xanthochorus cassidiformis) and the crab (Cancer polyodon) are harvested intensively. The impacts of harvesting these resources exclusively in the seagrass, sand-gravel, and in the sand habitats, as well as, in the seagrass and sand-gravel and in all habitats were assessed. The goal was to explore policies of sustainable exploitation of the benthic systems. 3.The most important findings were: (a) Fishing exclusively in either the seagrass or sand habitats produces a population increase in the sea star Luidia magallanica, in the seagrass Heterozostera tasmanica, and in the crab Paraxanthus barbiger. (b) Exclusive fishing in the sand-gravel habitat causes only small effects on the species and groups, which suggests that this habitat is the most resistant to harvest. (c) The simultaneous fishing on two or three habitats would produce the largest negative effect on the entire system. Therefore, a habitat rotation fishery is recommended. 4.Our study suggests that trophic-spatially explicit models offer great possibilities for the screening and planning of effective interventions or manipulations of natural systems. Copyright © 2002 John Wiley & Sons, Ltd. [source]


Evidence from traditional and new technologies for northward migrations of Australian plague locusts (Chortoicetes terminifera) (Walker) (Orthoptera: Acrididae) to western Queensland

AUSTRAL ECOLOGY, Issue 8 2005
E. D. DEVESON
Abstract The development of recent infestations of the Australian plague locust (Chortoicetes terminifera) (Walker) (Orthoptera: Acrididae) has been traced using traditional survey data combined with information from several modern technologies including simulation of windborne transport trajectories, direct observation with entomological radar and satellite imagery. The results indicate that migration from spring generations in the southern and eastern parts of the species range, including agricultural areas, to the summer rainfall areas in arid western Queensland (Qld) has contributed to the development of infestations on several occasions. Migration from swarm populations in New South Wales to western Qld in November and December 1999 contributed to a rapid population increase that, over a sequence of generations, led to the major infestation of agricultural areas in March and April 2000. There is evidence that northward migrations also occurred in 1995, 1997 and 2000. These contributed to the early summer populations in Qld, but did not result in large migrations to the south in autumn. These observations suggest that a pattern of exchange migration across much of the geographical range of the species between regions of winter and summer rainfall characterizes the spatial dynamics of this species. This pattern appears to be adaptive and suggests migration in C. terminifera is sustained by contemporary natural selection. [source]


The seasonal phenology of Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) in Queensland

AUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 3 2010
Sakuntala Muthuthantri
Abstract Bactrocera tryoni is a polyphagous fruit fly, originally endemic to tropical and subtropical coastal eastern Australia, but now also widely distributed in temperate eastern Australia. In temperate parts of its range, B. tryoni populations show distinct seasonal peaks driven by changing seasonal climates, especially changing temperature. In contrast to temperate areas, the seasonal phenology of B. tryoni in subtropical and tropical parts of its range is poorly documented and the role of climate unknown. Using a large, historical (1940s and 1950s) fruit fly trapping dataset, we present the seasonal phenology of B. tryoni at nine sites across Queensland for multiple (two to seven) years per site. We correlate monthly trap data for each site with monthly weather averages (temperature, rainfall and relative humidity) to investigate climatic influences. We also correlate observed population data with predicted population data generated by an existing B. tryoni population model. Supporting predictions from climate driven models, B. tryoni did show year-round breeding at most Queensland sites. However, contrary to predictions, there was a common pattern of a significant population decline in autumn and winter, followed by a rapid population increase in August and then one or more distinct peaks of abundance in spring and summer. Mean monthly fly abundance was significantly different across sites, but was not correlated with altitudinal, latitudinal or longitudinal gradients. There were very few significant correlations between monthly fly population size and weather variables (either for the corresponding month or for up to 3 months previously) for eight of the nine sites. For the southern site of Gatton fly population abundance was correlated with temperature. Results suggest that although climate factors may be influencing patterns of B. tryoni population abundance in southern subtropical Queensland, they are not explaining patterns of abundance in northern subtropical and tropical Queensland. In the discussion we focus on the role of other factors, particularly larval host plant availability, as likely drivers of B. tryoni abundance in tropical and subtropical parts of its range. [source]


Contrasting Population Dynamics of the Endemic New Caledonian Conifer Araucaria laubenfelsii in Maquis and Rain Forest

BIOTROPICA, Issue 4 2010
Lesley S. Rigg
ABSTRACT This study compares demographic parameters and population dynamics for high disturbance (maquis) and low disturbance (rain forest) environments of the montane conifer, Araucaria laubenfelsii, in New Caledonia. The establishment, growth, survival and reproduction of ca 2500 individuals were followed in permanent plots over 10 yr. Growth and survival rates for A. laubenfelsii show that it is a long-lived, slow growing tree, with evidence of suppression in the sapling size classes in mature rain forest. Growth rates for all size classes are generally faster in maquis than rain forest. Transition matrix analyses estimated positive rates of population increase (, values>1), with populations expanding in maquis, and stable in mature forest. Araucaria laubenfelsii is able to regenerate continuously in maquis and early successional rain forest, but recruitment is limited in older stands. Life table response experiment analyses showed that reproduction, and transitions from sapling to mature tree stage, contributed positively to , in maquis, but negatively in forest. Araucaria laubenfelsii on Mont Do can be considered a long-lived pioneer, with early maquis colonizers helping to drive succession from maquis to forest. While opportunities for recruitment decline with time as rain forest sites develop a closed canopy, occasional gap phase recruitment, combined with disturbance by cyclones, landslides and fire, provide opportunities to ensure species persistence. Understanding contrasting population dynamics of A. laubenfelsii in maquis and rain forest will better facilitate conservation management of this species, particularly given current high rates of land conversion and degradation in New Caledonia. Abstract in French is available at http://www.blackwell-synergy.com/loi/btp [source]


Is there a higher risk for herbivore outhreaks after cold mast years?

ECOGRAPHY, Issue 6 2000
An analysis of two plant/herbivore series from southern Norway
Historical data on two plant-herbivore interactions from southern Norway were used to test the hypothesis that the degree of herbivore outbreaks in post-mast years is negatively related to summer temperatures in the mast year, because plants are more depressed after a high seed production if temperatures and thus the photosynthetic activity is low. The plant species were the sessile oak Quercus petraea and the bilberry Vaceinium myrtillus. For the former species post-mast years were identified from reports given by the local forest authorities for the period 1930,48, and from acorn export curves for the period 1949,98, For the latter species, post-mast years were identified mainly from bilberry export curves for the period 1920,31, from game reports for the period 1932,78. and from diary notes for the period 1979,87. The herbivore species used were the green oak leaf roller moth Tortrix viridana and the capercaillie Tetrao urogallus. Eight moth outbreaks on oak forests were reported by the forest authorities in the period 1930,98, and they all started in a post-mast year of the sessile oak. There were however also eleven post-mast years without moth outbreaks. According to game reports, observations and autumn counts, all increases in the autumn population size of capercaillie during 1920 88 occurred in or after a year with high bilberry production. Among i8 post-mast years, there were seven with strong increase, seven with slight or moderate increase, and four with no increase. For both herbivore species, post-mast years with marked population increases had significantly lower summer temperatures in the preceding (mast) year than had post-mast years with no or slight increases. For moth populations there also was a negative effect of high temperatures in April, possibly because moth eggs tend to hatch too early relative lo budburst if spring temperatures are high. For the capercaillie, high amount of precipitation in June , July seemed to have some negative impact on the autumn population sizes, as also found in previous studies. [source]


Changes in equine hindgut bacterial populations during oligofructose-induced laminitis

ENVIRONMENTAL MICROBIOLOGY, Issue 5 2006
G. J. Milinovich
Summary In the horse, carbohydrate overload is thought to play an integral role in the onset of laminitis by drastically altering the profile of bacterial populations in the hindgut. The objectives of this study were to develop and validate microbial ecology methods to monitor changes in bacterial populations throughout the course of experimentally induced laminitis and to identify the predominant oligofructose-utilizing organisms. Laminitis was induced in five horses by administration of oligofructose. Faecal specimens were collected at 8 h intervals from 72 h before to 72 h after the administration of oligofructose. Hindgut microbiota able to utilize oligofructose were enumerated throughout the course of the experiment using habitat-simulating medium. Isolates were collected and representatives identified by 16S rRNA gene sequencing. The majority of these isolates collected belonged to the genus Streptococcus, 91% of which were identified as being most closely related to Streptococcus infantarius ssp. coli. Furthermore, S. infantarius ssp. coli was the predominant oligofructose-utilizing organism isolated before the onset of lameness. Fluorescence in situ hybridization probes developed to specifically target the isolated Streptococcus spp. demonstrated marked population increases between 8 and 16 h post oligofructose administration. This was followed by a rapid population decline which corresponded with a sharp decline in faecal pH and subsequently lameness at 24,32 h post oligofructose administration. This research suggests that streptococci within the Streptococcus bovis/equinus complex may be involved in the series of events which precede the onset of laminitis in the horse. [source]


Environmental ,loopholes' and fish population dynamics: comparative pattern recognition with focus on El Niño effects in the Pacific

FISHERIES OCEANOGRAPHY, Issue 4-5 2003
Andrew Bakun
Abstract A process of comparative pattern recognition is undertaken for the purpose of garnering insights into the mechanisms underlying some currently puzzling conundrums in fishery resource ecology. These include (a) out-of-phase oscillations between anchovies and sardines, (b) the remarkable fish productivity of the Peru,Humboldt marine ecosystem, (c) sardine population increases in the eastern Pacific during El Niños, (d) basin-wide synchronies in large-amplitude abundance variations, (e) characteristic spawning of large tuna species in poorly productive areas, (f) contrary trends in Pacific tropical tuna abundance during the 1970s and early 1980s. It is found that each of the items appears to become less enigmatic when the conceptual focus shifts from conventional trophodynamics to the idea that ,loopholes' in the fields of biological controls (i.e. of predators of early life stages), produced by poor ocean productivity or by disruptive environmental perturbations, may in fact lead to remarkable reproductive success. Implications include the following: (1) El Niño, rather than being an unmitigated disaster for Peruvian fisheries, may in the long run be a prime reason for the remarkable fishery productivity of the Peru,Humboldt large marine ecosystem. (2) Globally-teleconnected climatic trends or shifts might produce globally-coherent population expansions even when local environmental expressions may be quite different. (3) It may be unreasonable to expect any management methodologies to be able to keep the fish populations of highly climatically-perturbed systems such as the Peruvian LME always at stable high levels; an alternative approach, for example, might be to take optimal advantage of the transient opportunities afforded by the high fish productivity of such inherently erratic systems. [source]


Effects of drought on contrasting insect and plant species in the UK in the mid-1990s

GLOBAL ECOLOGY, Issue 1 2002
M. D. Morecroft
Abstract Aim We examined the effects of drought in the summer of 1995 and the subsequent year on contrasting species of plants, moths, butterflies and ground beetles. We tested whether population increases were associated with: (a) species of warm environments (b) species of dry environments (c) species with rapid reproduction (d) species with high rates of dispersal. Location The study was conducted at Environmental Change Network (ECN) sites throughout Great Britain and Northern Ireland. Methods Climate monitoring, recording of plant species in permanent plots, transect walking for butterflies, light trapping for moths and pitfall trapping for carabid beetles were used. Results There was an overall increase in the number of species recorded in permanent vegetation plots between 1994 and 1996, principally among the annual and biennial vascular plants, probably as a result of gap colonization in grasslands. Most butterfly and moth species increased between 1994 and 1995. Among the butterflies, a southern distribution and high mobility were associated with species tending to increase throughout the period 1994,96, whereas declining species tended to have a northern distribution. A similar number of carabid beetle species increased as decreased in the period 1994,96; decreasing species tended to be associated with lower temperatures and wetter soils. Conclusions Current climate change scenarios indicate that the incidence of droughts in the United Kingdom will increase. A series of dry, hot summers could lead to a rapid change in the population of some species although others, including many plants, may be more resilient. This may lead to complex changes in ecosystems and needs to be considered in planning conservation strategies. [source]


Implications of mitochondrial DNA polyphyly in two ecologically undifferentiated but morphologically distinct migratory birds, the masked and white-browed woodswallows Artamus spp. of inland Australia

JOURNAL OF AVIAN BIOLOGY, Issue 6 2006
Leo Joseph
The white-browed woodswallow Artamus superciliosus and masked woodswallow A. personatus (Passeriformes: Artamidae) are members of Australia's diverse arid- and semi-arid zone avifauna. Widely sympatric and among Australia's relatively few obligate long-distance temperate-tropical migrants, the two are well differentiated morphologically but not ecologically and vocally. They are pair breeders unlike other Artamus species, which are at least facultative cooperative breeders. For these reasons they are an excellent case in which to use molecular data in integrative study of their evolution from ecological and biogeographical perspectives. We used mitochondrial DNA (mtDNA) to test whether they are each other's closest relatives, whether they evolved migration independently, whether they have molecular signatures of population expansions like some other Australian arid zone birds, and to estimate the timing of any inferred population expansions. Their mtDNAs are monophyletic with respect to other species of Artamus but polyphyletic with respect to each other. The two species appear not to have evolved migration independently of each other but their morphological and mtDNA evolution have been strongly decoupled. Some level of hybridization and introgression cannot be dismissed outright as being involved in their mtDNA polyphyly but incomplete sorting of their most recent common ancestor's mtDNA is a simpler explanation consistent with their ecology. Bayesian phylogenetic inference and analyses of diversity within the two species (n=77) with conventional diversity statistics, statistical parsimony, and tests for population expansion vs stability (Tajima's D, Fu's Fs and Ramos-Onsin and Rozas's R2) all favour recent population increases. However, a non-starlike network suggests expansion(s) relatively early in the Pleistocene. Repeated population bottlenecks corresponding with multiple peaks of Pleistocene aridity could explain our findings, which add a new dimension to accruing data on the effects of Pleistocene aridity on the Australian biota. [source]


A policy tool for establishing a balance between wildlife habitat preservation and the use of natural resources by rural people in South Africa

AFRICAN JOURNAL OF ECOLOGY, Issue 1 2006
Oumar Bouare
Abstract In this paper, a model is set up to determine the size of the wildlife population compatible with the extraction of the maximum output by rural people from natural resources. It is found that when the size of human population increases, to obtain the maximum output of food, the size of wildlife population decreases if the human population is growing faster than or at the same rate as that of the wildlife population; whereas the size of the wildlife population increases if the human population is growing slower than that of the wildlife. Furthermore, in the event that the increase in the size of the wildlife population is unable to reach the level compatible with the extraction of the maximum output of food, the improvement of the wildlife habitat and supplementing rural people's income with the proceeds of tourism are proposed as policies to maintain a balance between the preservation of the wildlife habitat and the use of natural resources by rural people. Résumé Dans cette étude un modèle est établi afin de déterminer la taille de la population faunique compatible avec l'extraction de la quantité maximale des ressources naturelles par les peuples ruraux. Les résultats montrent que quand la taille de la population humaines accroît, afin d'obtenir la quantité maximale de nourriture, la taille de la population faunique décroît si la population humaine augmente plus vite que, ou à la même vitesse que, la population faunique. Tomdis que, la population faunique saccroît si la croissance de la population humaine est plus lente. De plus, si la croissance de la taille de la population faunique n'atteint pas le niveau compatible avec l'extraction de la quantité maximale de nourriture, l'amélioration de l'habitat faunique et le rajout de recettes du tourisme aux revenus des peuples ruraux sont conseillés comme politiques afin de maintenir un équilibre entre la préservation de l'habitat faunique et l'utilisation des ressources naturelles par les peuples ruraux. [source]