Water stress, root herbivory and above-ground multitrophic interactions in a crucifer-aphid system

Plants, insect herbivores and their natural enemies interact in multitrophic food webs that can be influenced by various stress factors. The aim of the present study was to understand the effects of two different below-ground stress factors (drought and root herbivory) on the performance of two above-ground herbivores, a generalist (Myzus persicae) and a specialist (Brevicoryne brassicae) aphid species and two of their natural enemies, a generalist (Aphidius colemani) and a specialist (Diaeretiella rapae) parasitoid species. Preliminary experiments with various Brussels sprout (Brassica oleracea) cultivars (cv) showed that aphid performance was influenced both by host plant on which the parent aphid had been reared and by the host plant on which it was feeding when reproducing. The Brussels sprout cv. Oliver was selected as a consistently good aphid host for subsequent experiments. Root herbivory and drought stress were shown to significantly affect the outcome of plant-mediated interactions between insect herbivores and their parasitoids. High drought stress had a negative impact on the aphid species and their parasitoids and also reduced performance of a root herbivore, the cabbage root fly, Delia radicum. Root herbivory alone or in combination with drought significantly altered foliar herbivore performance. High drought stress combined with high D. radicum density had a negative impact on foliar herbivore performance and parasitoid preference and performance. Plant volatiles and parasitoid preference were shown to decrease with drought stress and root herbivory. Plant foliar glucosinolate, nitrogen and carbon concentrations were significantly affected by drought stress. Relative water content and plant biomass were significantly affected by both stresses. The present study on a Brassica-aphid system underlines the importance of root herbivory and drought stress in mediating interactions between plant, foliar herbivores and their parasitoids. The implications of these findings for multitrophic interactions under potential climate change are discussed with particular reference to pest management

Studies to elucidate the relative role of single and multiple-event types of radiation damage in Vicia Faba (L)

Imperial Users onl

Corruption and financial intermediation in a panel of regions: cross-border effects of corruption

The importance of financial market reforms in combating corruption has been highlighted in the theoretical literature but has not been systemically tested empirically. In this study we provide a first pass at testing this relationship using both linear and non-monotonic forms of the relationship between corruption and financial intermediation. Our study finds a negative and statistically significant impact of financial intermediation on corruption. Specifically, the results imply that a one standard deviation increase in financial intermediation is associated with a decrease in corruption of 0.20 points, or 16 percent of the standard deviation in the corruption index and this relationship is shown to be robust to a variety of specification changes, including: (i) different sets of control variables; (ii) different econometrics techniques; (iii) different sample sizes; (iv) alternative corruption indices; (v) removal of outliers; (vi) different sets of panels; and (vii) allowing for cross country interdependence, contagion effects, of corruption.corruption; contagion effects; financial Intermediation; panel data

Corruption and the military in politics: theory and evidence from around the world

Recent theoretical developments and case study evidence suggests a relationship between the military in politics and corruption. This study contributes to this literature by analyzing theoretically and empirically the role of the military in politics and corruption for the first time. By drawing on a cross sectional and panel data set covering a large number of countries, over the period 1984-2007, and using a variety of econometric methods substantial empirical support is found for a positive relationship between the military in politics and corruption. In sum, our results reveal that a one standard deviation increase in the military in politics leads to a 0.22 unit increase in corruption index. This relationship is shown to be robust to a variety of specification changes, different econometric techniques, different sample sizes, alternative corruption indices and the exclusion of outliers. This study suggests that the explanatory power of the military in politics is at least as important as the conventionally accepted causes of corruption, such as economic development.corruption; military in politics; cross sectional; panel data

The Effect of Foreign Remittances on Schooling: Evidence from Pakistan

The underlying study intends to show the impact of foreign remittances on the educational performance of children in the households receiving these remittances. Much of the literature in this area covers the effects of remittances on poverty, consumption, and investment behaviour of the receiving households. The literature on the impact of remittances on educational performance, however, is rare, especially in Pakistan. To investigate the impact of remittances on educational performance, primary data at the household level is collected from four main cities of the Khyber Pakhtunkhwa Province, Pakistan. The OLS results illustrate that, without considering parental education, remittances have significant adverse effects on educational performance. However, the effect becomes insignificant once parental education is included, as a control variable, in the regression. The results also reveal that the low level of parental education, current income, assets, family type, and family size play an important role in the educational performance of children.Remittances , Education, Parental Absence

The Demand for Simple-sum and Divisia Monetary Aggregates for Pakistan: A Cointegration Approach

Financial liberalisation and the advance of financial innovation in a number of developed economies has been blamed for the break-down in the demand for money based on simple sum measures. This break-down has prompted research into Divisia measures of the demand for money. Like many developing countries, Pakistan is going through a period of financial deregulation which goes hand in hand with financial innovation due to increased competition in the banking industry. This paper employs the methodology of cointegration to compare simple-sum and Divisia level estimates of the demand for money for Pakistan for the period 1974Q4 to 1992Q4. Simple sum measures of M1 and M2 were compared with Divisia versions. The paper reports little evidence in support of the superiority of the Divisia monetary aggregates. Both types of measure produce a stable demand for money and perform satisfactorily in post-sample stability tests, although the Divisia measure appears to perform marginally better on conventional statistical criteria. However, our conclusions have to be qualified by the limitations of the data and the knowledge that the period of financial innovation and deregulation has been relatively recent. The policy significance of the results suggests that currently there is no advantage from switching from simple-sum to Divisia aggregates at the existing level of official aggregation as the proper indicator of monetary policy. However, if financial deregulation and innovation continues at the current pace, the Divisia aggregates may in future prove to be the better indicator.