Mother really knows best: host choice of adult phytophagous insect females reflects a within-host variation in suitability as larval food

Non-random distribution patterns of specialized phytophagous insects on their hosts may depend on intraspecific differences in plant tissue quality, including nutrients and secondary compounds. Secondary compounds are involved in plant resistance, but are also important for the recognition and acceptability of plants as resources by specialized insects. If individuals within a plant species vary in their content of such secondary substances, there may also be qualitative differences between them. In such cases, natural selection will favor insects with the ability to distinguish and prefer the more suitable plants. In Sweden, the leaf beetle Gonioctena linnaeana Schrank (Coleoptera, Chrysomelidae) is highly specialized on one host, the native willow Salix triandra L (Salicaceae). Field observations reveal that some host plants in a population harbor many feeding larvae, causing severe defoliation, whereas neighboring plants may have few or no feeding larvae. Our hypothesis is that the distribution pattern of G. linnaeana larvae in this population results from qualitative differences between individual host plants in combination with the ability of G. linnaeana females to distinguish between plants that are suitable and not suitable for offspring performance. We examine whether larval survival differs depending on diet and whether the content of secondary chemical compounds explains female preference. Based on the higher survival rate of larvae reared on leaves from preferred hosts, we conclude that G. linnaeana females have evolved a behavior that maximizes offspring performance and thus positively affects female fitness. A chemical survey of the plants indicates that luteolin-7-glucoside and an unidentified flavonoid are important for separating the preferred from the non-preferred plants.     

The role of DDE,PCB, coplanar PCB and eggshell parameters for reproduction in the white-tailed sea eagle (Haliaeetus albicilla) in Sweden

The reproduction of white-tailed sea eagles was monitored in 1964-1999 in 3 differently contaminated sub-populations: Baltic Sea coast (Bp), inland central Sweden (Ip) and Lapland (Lp). 249 dead eggs from 205 clutches were obtained for analyses of DDE and PCBs and for eggshell measurements. A desiccation index (Di) value was calculated for each egg as a measure of water loss through the shell. In the highly contaminated Bp, p,p'-DDE concentrations in the eggs decreased continuously and 5-fold during the study period and PCB concentrations decreased 3-fold from the mid 1980s. The PCB pattern changed slightly over time towards more high-chlorinated congeners but the relative toxicity of the PCB mixture, expressed as 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQ), remained constant and TEQ can be assumed to have decreased in a similar way as PCB over time. Productivity (P), shell thickness (St), shell index (Si) and Di increased over time in the Bp but no change in Di or productivity occurred in the Lp, where residue concentrations were 5-8 times lower. P of the Bp was not correlated to St or Si but was negatively correlated to Di, DDE and PCB. An S-shaped dose-response relationship was indicated between P and DDE. After 1988, when the PCB/DDE ratio was considerably higher than previously, PCB but not DDE concentrations were significantly higher in eggs with dead embryos as compared to undeveloped eggs, implying lethal concentrations of PCB, and a LOEL of 320 pg g-1 TEQ is suggested for embryo mortality. In a subset of 21 eggs, representing productive and unproductive females, analyzed for a selection of coplanar PCB congeners, tris(4-chlorophenyl) methanol and bis(4-chlorophenyl) sulphone, there was no evidence for a correlation between P and any of these compounds. A reduction in residue concentrations in old females did not lead to increased P or improved Di-values, indicating a remaining effect from a previous, higher exposure to contaminants. The inability to reproduce included a high rate of undeveloped eggs, indicating effects at a prezygotic stage. P showed the strongest correlation with Di, and Di was most strongly correlated to DDE. Thus, the remaining effect of previous exposure resulted in a stronger correlation to the symptom (Di) rather than to the suggested causative agent (DDE). LOEL values for depressed P were estimated at 120 micrograms g-1 DDE and 500 micrograms g-1 PCB (lipid basis). It is concluded that the major reason for depressed P during the study period was DDE, but that effects also from PCB were largely concealed by the effects from DDE.     

Regional scale evidence for improvements in surface water chemistry 1990-2001

The main aim of the international UNECE monitoring program ICP Waters under the Convention of Long-range Transboundary Air Pollution (CLRTAP) is to assess, on a regional basis, the degree and geographical extent of the impact of atmospheric pollution, in particular acidification, on surface waters. Regional trends are calculated for 12 geographical regions in Europe and North America, comprising 189 surface waters sites. From 1990-2001 sulphate concentrations decreased in all but one of the investigated regions. Nitrate increased in only one region, and decreased in three North American regions. Improvements in alkalinity and pH are widely observed. Results from the ICP Waters programme clearly show widespread improvement in surface water acid-base chemistry, in response to emissions controls programs and decreasing acidic deposition. Limited site-specific biological data suggest that continued improvement in the chemical status of acid-sensitive lakes and streams will lead to biological recovery in the future.     

A Novel Environmental Quality Criterion for Acidification in Swedish Lakes – An Application of Studies on the Relationship Between Biota and Water Chemistry

The recovery from acidification has led to the demand for more precise criteria for classification of acidification. The Swedish Environmental Protection Agency has revised Sweden’s Ecological Quality Criteria for acidification to improve the correlation between the chemical acidification criteria and biological effects. This paper summarises the most relevant findings from several of the studies commissioned for this revision. The studies included data on water chemistry in 74 reference lakes in southern Sweden with data on fish in 61 of the lakes, as well as data on littoral fauna in 48 lakes. We found that the acidity variable most strongly correlated to the biota was the median pH from the current year. Our results probably do not reflect the mechanisms behind the negative effects of acidity on the biota, but are fully relevant for evaluation of monitoring data. The biogeochemical models used for predicting acidification reference conditions generate a pre-industrial buffering capacity. In order to get an ecologically more relevant criteria for acidification based on pH, we transferred the estimated change in buffering capacity into a corresponding change in pH. A change of 0.4 units was defined as the threshold for acidification. With this criterion a considerably lower number of Swedish lakes were classified as acidified when compared with the present Ecological Quality Criteria.     

The spatiotemporal sequencing of everyday activities in the large-scale environment

Choices of where to carry out everyday activities in large-scale environments were conceptualized as a process of forming ‘travel plans’, and, to test a model of how such plans are formed, three experimental simulations of a planning task were performed in the laboratory. In Experiment 1, subjects (high school students) were found to choose a shortest route to travel between a number of actual, familiar locations in a town by first choosing the order between the locations that minimized straight-line (Euclidean) distances, then choosing the shortest paths between the locations in the constrained order. The order choices were, in Experiment 2, found to be made by minimizing distance locally rather than globally, except in some cases when ‘spatial configurations’ of the locations were discovered. Both the results of this experiment and of Experiment 3 suggested that such discoveries were facilitated by a simultaneous representation of the locations which was possible when they were positions on a display, committed to short-term memory or available for perceptual inspection, but to a less extent when they were actual locations.     

Nest defenses and egg recognition of yellow-bellied prinia against cuckoo parasitism

Parasites may, in multi-parasite systems, block the defenses of their hosts and thus thwart host recognition of parasites by frequency-dependent selection. Nest defenses as frontline may block or promote the subsequent stage of defenses such as egg recognition. We conducted comparative studies of the defensive strategies of a host of the Oriental cuckoo Cuculus optatus, the yellow-bellied prinia Prinia flaviventris, in mainland China with multiple species of cuckoos and in Taiwan with a single cuckoo species. Cuckoo hosts did not exhibit aggression toward cuckoos in the presence of multiple cuckoo species but showed strong aggressive defenses of hosts directed toward cuckoos in Taiwan. Furthermore, the cuckoo host in populations with a single cuckoo species was able to distinguish adults of its brood parasite, the Oriental cuckoo, from adult common cuckoos (Cuculus canorus). This represents the first case in which a cuckoo host has been shown to specifically distinguish Oriental cuckoo, from other Cuculus species. Hosts ejected eggs at a higher rate in a single cuckoo species system than in a multi-species cuckoo system, which supports the strategy facilitation hypothesis. Granularity analysis of variation in egg phenotype based on avian vision modeling supported the egg signature hypothesis in hosts because Taiwanese prinias increased consistency in the appearance of their eggs within individual hosts thus favoring efficient discrimination against cuckoo eggs. This study significantly improves our knowledge of intraspecific variation in antiparasitism behavior of hosts between single- and multi-cuckoo systems.     

Practicing for and performance on drivers license tests in relation to gender differences in crash involvement among novice drivers

PROBLEM: Young male novice drivers are overrepresented in injury motor-vehicle crashes compared to females in the same category. This difference in crash involvement is often assumed to include factors such as overestimation, risk acceptance, and sensation seeking, but it can also be related to acquisition of knowledge, skills, insight, and driving experience. Therefore, this study explored possible gender differences among 18-24-year-olds in Sweden regarding practicing as learners, outcome of the driver's tests, and crash involvement during the first year after licensure. METHOD: Data for 2005 from different sources (e.g., questionnaires, license test, and crash statistics) were examined. It was not possible to follow individual subjects through all stages or in all analyses. Nevertheless, the study design did enable scrutinization and discussion of gender differences between younger inexperienced drivers with respect to education and training, license test results, and initial period of licensure. RESULTS: Males and females assimilated tuition in different ways. Females studied more theory, pursued training in a more structured manner, practiced more elements of driving in several different environments, and participated more extensively in driving school instruction. National statistics showed that females did better on the written test but not on the driving test. Males were involved in 1.9 more injury crashes per 1,000 drivers than females during their first year of licensed driving. The proportional distribution of crash types was the same for both sexes during the first period as novice drivers, but the circumstances surrounding the accidents varied (e.g., males were involved in more night crashes). IMPACT ON TRAFFIC SAFETY: More structured training while learning appears to be one of the reasons why females initially do better than males as novice drivers. Therefore, in the future, driver education should focus not only on matters such as the amount of time spent on training and preconditioning, but also on the importance of the organization and content of the learning process.