Utility of Expert-Based Knowledge for Predicting Wildlife-Vehicle Collisions

ABSTRACT Wildlife-vehicle collisions have important ecological, economic, and social effects. In North America and across northern Europe, moose (Alces alces) are one of the largest ungulates hit by motor vehicles. The force and increasing frequency of these collisions has resulted in a commitment by wildlife and transportation agencies to limit or reduce causal factors. In an effort to improve these mitigation strategies, we used the most readily available source of knowledge of collision factors, expert opinion, to develop a series of models that explained and predicted location of moose-vehicle collisions (MVC). We developed expert-based models using the Analytical Hierarchy Process (AHP) and we used a structured survey approach where experts could assess criteria relevancy, weight criteria, and review weights for consistency. We hypothesized that collisions were the product of habitat- or driver-related factors and we formulated the survey accordingly. We used the receiver operating characteristic to validate the resulting models and the Kappa index of agreement to quantify differences among spatial predictions originating from the experts. Local and nonlocal experts weighted the moose habitat classification as the most important criterion for identifying MVC. Among driver-related criteria, speed limit was weighted as the most important factor. Overall, habitat-based models were more proficient than driver-based models in predicting MVC within Mount Revelstoke and Glacier National Parks, Canada. Both local and nonlocal expert models were excellent predictors of MVC, with local experts slightly outperforming nonlocal experts. Considering that habitat-related criteria were more powerful for predicting MVC, and that habitat can vary considerably across study areas, we suggest that local experts be used when possible. The AHP is a valuable tool for wildlife, highway, and park managers to better understand why and where wildlife-vehicle collisions occur. Adopting this process, our data suggested that MVC were most strongly correlated with highway attractants associated with habitat. Vegetation management or alternative routing could minimize spatial juxtaposition of moose and motor vehicles.     

CO2-mediated changes in aspen chemistry: effects on gypsy moth performance and susceptibility to virus

We investigated the effects of long-term CO₂ enrichment on foliar chemistry of quaking aspen ( Populus tremuloides ) and the consequences of chemical changes for performance of the gypsy moth ( Lymantria dispar ) and susceptibility of the gypsy moth to a nucleopolyhedrosis virus (NPV). Foliage was collected from outdoor open-top chambers and fed to insects in a quarantine rearing facility. Under enriched CO₂, levels of leaf nitrogen declined marginally, levels of starch and phenolic glycosides did not change, and levels of condensed tannins increased. Long-term bioassays revealed reduced growth (especially females), prolonged development and increased consumption in larvae fed high-CO₂ foliage but no significant differences in final pupal weights or female fecundity. Short-term bioassays showed weaker, and sex-specific, effects of CO₂ treatment on larval performance. Correlation analyses revealed strong, negative associations between insect performance and phenolic glycoside concentrations, independent of CO₂ treatment. Larval susceptibility to NPV did not differ between CO₂ treatments, suggesting that effects of this natural enemy on gypsy moths are buffered from CO₂-induced changes in foliar chemistry. Our results emphasize that the impact of enriched CO₂ on plant–insect interactions will be determined not only by how concentrations of plant compounds are altered, but also by the relevance of particular compounds for insect fitness. This work also underscores the need for studies of genetic variation in plant responses to enriched CO₂ and long-term population-level responses of insects to CO₂-induced changes in host quality.     

Epigenetic Regulation of Programmed Genomic Rearrangements in Paramecium aurelia1

ABSTRACT In ciliates, development of the polyploid somatic macronucleus after sexual events involves extensive and reproducible rearrangements of the germ-line genome, including chromosome fragmentation and precise excision of numerous internal sequence elements. In Paramecium aurelia, alternative macronuclear versions of the same germ-line genome can be maternally inherited across sexual generations, showing that rearrangement patterns are not strictly determined by the germ-line sequence. Homology-dependent maternal effects can be evidenced by transformation of the vegetative macronucleus with cloned macronuclear sequences: new fragmentation patterns or internal deletions are specifically induced during differentiation of a new macronucleus, in sexual progeny of transformed clones. Furthermore, transformation of the maternal macronucleus with germ-line sequences containing internal eliminated sequences (short single-copy elements) can result in a specific inhibition of the excision of the same elements in the zygotic macronucleus. These experiments show that the processing of many germ-line sequences in the developing macronucleus is sensitive to the structure and copy number of homologous sequences in the maternal macronucleus. The generality and sequence specificity of this trans-nuclear, epigenetic regulation of rearrangements suggest that it is mediated by pairing interactions between germ-line sequences and sequences imported from the maternal macronucleus.     

Aphid–ant mutualism: how honeydew sugars influence the behaviour of ant scouts

Honeydew is the keystone on which ant–aphid mutualism is built. The present study investigates how each sugar identified in Aphis fabae Scopoli honeydew acts upon the feeding and the laying of a recruitment trail by scouts of the aphid‐tending ant Lasius niger Linnaeus, and thus may enhance collective exploitation by the ant mutualists. The feeding preferences shown by L. niger for honeydew sugars are: melezitose = sucrose = raffinose > glucose = fructose > maltose = trehalose = melibiose = xylose. Although feeding is a prerequisite to the launching of trail recruitment, the reverse is not necessarily true: not all ingested sugar solutions elicit a trail‐laying behaviour among fed scouts. Trail mark laying is only triggered by raffinose, sucrose or melezitose, with the latter sugar being specific to honeydew. By comparing gustatory and recruitment responses of ant foragers to sugar food sources, the present study clarifies the role of honeydew composition both as a source of energy and as a mediator in ant–aphid interactions. Lasius niger feeding preferences can be related to the physiological suitability of each sugar (i.e. their detection by gustatory receptors as well as their ability to be digested and converted into energy). Regarding recruitment, the aphid‐synthesized oligosaccharide (melezitose) could be used by ant scouts as a cue indicative of a long‐lasting productive resource that is worthy of collective exploitation and defence against competitors or aphid predators.     

Thermal acclimation of photosynthesis: a comparison of boreal and temperate tree species along a latitudinal transect

Common gardens were established along a ～900 km latitudinal transect to examine factors limiting geographical distributions of boreal and temperate tree species in eastern North America. Boreal representatives were trembling aspen (Populus tremuloides Michx.) and paper birch (Betula papyrifera Marsh.), while temperate species were eastern cottonwood (Populus deltoides Bartr ex. Marsh var. deltoides) and sweetgum (Liquidambar styraciflua L.). The species were compared with respect to adjustments of leaf photosynthetic metabolism along the transect, with emphasis on temperature sensitivities of the maximum rate of ribulose bisphosphate (RuBP) carboxylation (E_V) and regeneration (E_J). During leaf development, the average air temperature (T_growth) differed between the coolest and warmest gardens by 12 °C. Evidence of photosynthetic thermal acclimation (metabolic shifts compensating for differences in T_growth) was generally lacking in all species. Namely, neither E_V nor E_J was positively related to T_growth. Correspondingly, the optimum temperature (T_opt) of ambient photosynthesis (A_sat) did not vary significantly with T_growth. Modest variation in T_opt was explained by the combination of E_V plus the slope and curvature of the parabolic temperature response of mesophyll conductance (g_m). All in all, species differed little in photosynthetic responses to climate. Furthermore, the adaptive importance of photosynthetic thermal acclimation was overshadowed by g_m's influence on A_sat's temperature response.     

Thick Root Syndrome in Cucumber (Cucumis sativus L.): A Description of the Phenomenon and an Investigation of the Role of Ethylene

In commercial growth of horticultural plants in greenhouses,high financial losses are being suffered due to the so-calledthick root syndrome (TRS), a phenomenon characterized by severedeterioration of the root system. The early symptoms of TRSin cucumber (Cucumis sativus L.) are strongly curving rootsthat are swollen and superficially damaged. Research focusedon ethylene, as both the culture practice of cucumber and theknown effects of ethylene on root growth point to a possiblerole for this phytohormone in TRS. Ethylene induced root curvatureand swelling as well as damage of the epidermal layer and outercortex of roots of cucumber plants similar to TRS symptoms.Formation of root hairs was stimulated and root elongation wasalso severely inhibited by exogenous ethylene. However, basedon experiments with the ethylene inhibitor