Carcass Persistence and Detectability: Reducing the Uncertainty Surrounding Wildlife-Vehicle Collision Surveys

Carcass persistence time and detectability are two main sources of uncertainty on roadkill surveys. In this study, we evaluate the influence of these uncertainties on roadkill surveys and estimates. To estimate carcass persistence time, three observers (including the driver) surveyed 114km by car on a monthly basis for two years, searching for wildlife-vehicle collisions (WVC). Each survey consisted of five consecutive days. To estimate carcass detectability, we randomly selected stretches of 500m to be also surveyed on foot by two other observers (total 292 walked stretches, 146 km walked). We expected that body size of the carcass, road type, presence of scavengers and weather conditions to be the main drivers influencing the carcass persistence times, but their relative importance was unknown. We also expected detectability to be highly dependent on body size. Overall, we recorded low median persistence times (one day) and low detectability (<10%) for all vertebrates. The results indicate that body size and landscape cover (as a surrogate of scavengers’ presence) are the major drivers of carcass persistence. Detectability was lower for animals with body mass less than 100g when compared to carcass with higher body mass. We estimated that our recorded mortality rates underestimated actual values of mortality by 2–10 fold. Although persistence times were similar to previous studies, the detectability rates here described are very different from previous studies. The results suggest that detectability is the main source of bias across WVC studies. Therefore, more than persistence times, studies should carefully account for differing detectability when comparing WVC studies.     

Body condition is associated with adrenocortical response in the barn swallow (Hirundo rustica L.) during early stages of autumn migration

Migration is an energy-demanding life-history period and also a significant population-limiting factor of long-distance migratory birds. It is important to understand how corticosterone, the main energy regulating hormone in birds, is associated with behavioural and physiological changes during migration. According to the migration modulation hypothesis (MMH), individual birds may express elevated levels of baseline corticosterone to facilitate fuelling, but down-regulate the adrenocortical response in order to protect skeletal muscles from the catabolic effects of the hormone. We measured the baseline and stress-induced levels of corticosterone in barn swallows (Hirundo rustica L.) during early stages of autumn migration. Here, we show that, while barn swallows clearly responded to the capture and handling stress by increasing the corticosterone level, the strength of this acute response was related to their energetic condition: birds with high body mass responded more rapidly and had lower peak values of corticosterone than lighter birds. Further, the baseline levels of corticosterone correlated negatively with the magnitude of the adrenocortical response. Barn swallows did not show elevated baseline levels of corticosterone in the course of autumn, which suggests that, instead of fuelling, the birds were actively migrating. Our results indicate that MMH also applies to aerial feeders, whose foraging habits differ from model birds of previous studies.     

Gene expression and metabolite profiling of Populus euphratica growing in the Negev desert

Background

Plants growing in their natural habitat represent a valuable resource for elucidating mechanisms of acclimation to environmental constraints. Populus euphratica is a salt-tolerant tree species growing in saline semi-arid areas. To identify genes involved in abiotic stress responses under natural conditions we constructed several normalized and subtracted cDNA libraries from control, stress-exposed and desert-grown P. euphratica trees. In addition, we identified several metabolites in desert-grown P. euphratica trees.

Results

About 14,000 expressed sequence tag (EST) sequences were obtained with a good representation of genes putatively involved in resistance and tolerance to salt and other abiotic stresses. A P. euphratica DNA microarray with a uni-gene set of ESTs representing approximately 6,340 different genes was constructed. The microarray was used to study gene expression in adult P. euphratica trees growing in the desert canyon of Ein Avdat in Israel. In parallel, 22 selected metabolites were profiled in the same trees.

Conclusion

Of the obtained ESTs, 98% were found in the sequenced P. trichocarpa genome and 74% in other Populus EST collections. This implies that the P. euphratica genome does not contain different genes per se, but that regulation of gene expression might be different and that P. euphratica expresses a different set of genes that contribute to adaptation to saline growth conditions. Also, all of the five measured amino acids show increased levels in trees growing in the more saline soil.     

Origin of Phospholipid in Bacteriophage PM2

Phosphatidylethanolamine is the only phosphatide present in purified bacteriophage PM2 when obtained from bacteria grown and infected in minimal medium. The growth cycle of bacteriophage PM2 shows the basic general features described for virulent bacteriophages. PM2 infection of Pseudomonas BAL-31 causes a pronounced increase in deoxyribonucleic acid synthesis, but no detectable effect on the incorporation of phosphorus into lipid. When (32)P-prelabeled bacteria are infected with PM2, the specific activity of the phosphatide phosphorus in the virus is almost the same as that in the host bacteria labeled before infection. It is concluded that the viral phosphatide is not synthesized de novo after infection, but it probably is derived from preexisting cellular phosphatidylethanolamine.     

Application of Multivariate Analysis for the Selection of Candidates for Biological Control Agents

A survey of natural enemies ofSenna obtusifolia(Leguminosae: Cesalpinaceae) was made in 46 localities in Brazil. Twenty-one preselected insect species were used in a multivariate analysis in a search for potential biocontrol agents, based on frequency of occurrence of each species, degree of insect/host association, and damage level. Insect communities were organized in a binary matrix (presence/absence of the species); measures of distance and similarities were based on the Jaccard coefficient, and cluster analysis was then conducted. Construction of a dendogram showed similarities among geographically close localities where phenological stages of sicklepod plants were similar. Analysis of correspondence based on the correlation matrix showed that Eigen values of the three first axes explain only 40.1% of the observed variation. Correlation among the scores produced by species Eigenvectors in each locality on axis 1 and the latitude, altitude, and phenological stage showed that only phenological stage was correlated (r = 0.45,P = 0.02). The results indicate that weather will not be a limiting factor for the establishment of these insect species in an environmental gradient similar to that of the surveyed area (12 to 22° latitude and 6 to 1200 m altitude). Distribution in the ordinal space of axes 1 and 2 showed thatAgrilus oceanicum(Buprestidae),Fundella argentina(Pyralidae),Thyphedanus undulatus(Hesperidae), andPhoebis sennae(Pieridae) are grouped and separated from the others in axis 2, suggesting that these species co-occur with each other. Based on their feeding guilds, multiple introduction of these species can be considered. Multivariate analysis showed potential to be used as an additional tool to help in the selection of candidates for biocontrol agents.     

Structural and image analysis of a crystalline layer from dipteran eggshell.

A crystalline layer has been identified as a constituent of the eggshell in the dipteran Drosophila melanogaster. This 400A thick intermediate chorionic layer (ICL) is composed of eight 50A thick sublayers and lies between the vitelline membrane and the endochorion. Whole mount views of isolated ICL after negative staining reveal P2 planar periodicity which, when analyzed further by optical diffraction and filtering, showed 1st (100A), 2nd, 3rd and 4th order reflections.     

Egg quality and female condition in vendace (Coregonus albula L.) before and during spawning

The fat content of muscle, liver and eggs of vendace (Coregonus albula L.) were measured during the maturation of ovaries in summer. The fat content of eggs was at its highest in July and that of muscle in August during the optimal feeding season. Significant differences were not found in fat content between lakes Suvasvesi and Southern-Kallavesi in central Finland. There were no essential differences in fatty acid composition between muscle, liver and eggs of Lake Suvasvesi vendace. During the last month before spawning in October the gross energy and fat contents of eggs decreased in Lake Suvasvesi vendace. The fat and vitamin C contents of muscle as well as the liver index of females decreased during this time also. In males the corresponding decrease did not occur, indicating that spawning is a greater stress for females than for males. The egg quality and condition of Lake Inarijärvi vendace were about the same as those of Lake Suvasvesi vendace. The unfavourable conditions of Lake Inarijärvi, located in northern Finland, are reflected in the size of ovaries, which is known to be smaller (gonadosomatic index < 20%) than in Lake Suvasvesi (GSI 26–27%). Vendace, then, maintain the quality of eggs at the expense of their number.