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71.
72.
Counterintuitive density-dependent growth in a long-lived vertebrate after removal of nest predators
Examining the phenotypic and genetic underpinnings of life-history variation in long-lived organisms is central to the study of life-history evolution. Juvenile growth and survival are often density dependent in reptiles, and theory predicts the evolution of slow growth in response to low resources (resource-limiting hypothesis), such as under densely populated conditions. However, rapid growth is predicted when exceeding some critical body size reduces the risk of mortality (mortality hypothesis). Here we present results of paired, large-scale, five-year field experiments to identify causes of variation in individual growth and survival rates of an Australian turtle (Emydura macquarii) prior to maturity. To distinguish between these competing hypotheses, we reduced nest predators in two populations and retained a control population to create variation in juvenile density by altering recruitment levels. We also conducted a complementary split-clutch field-transplant experiment to explore the impact of incubation temperature (25 degrees or 30 degrees C), nest predator level (low or high), and clutch size on juvenile growth and survival. Juveniles in high-recruitment (predator removal) populations were not resource limited, growing more rapidly than young turtles in the control populations. Our experiments also revealed a remarkably long-term impact of the thermal conditions experienced during embryonic development on growth of turtles prior to maturity. Moreover, this thermal effect was manifested in turtles approaching maturity, rather than in turtles closer to hatching, and was dependent on population density in the post-hatching rearing environment. This apparent phenotypic plasticity in growth complements our observation of a strong, positive genetic correlation between individual body size in the experimental and control populations over the first five years of life (rG - +0.77). Thus, these Australian pleurodiran turtles have the impressive capacity to acclimate plastically to major demographic perturbations and enjoy the longer-term potential to evolve adaptively to maintain viability. 相似文献
73.
The stereoisomers of metolachlor and its two polar metabolites [ethane sulfonic acid (ESA) and oxanilic acid (OXA)] were separated using liquid chromatography-mass spectrometry (LC-MS) and capillary zone electrophoresis (CZE), respectively. The separation of metolachlor enantiomers was achieved using a LC-MS equipped with a chiral stationary phase based on cellulose tris(3,5-dimethylphenyl carbamate) and an atmospheric pressure chemical ionization source operated under positive ion mode. The enantiomers of ESA and OXA were separated using CZE with gamma-cyclodextrin (gamma-CD) as chiral selector. Various CZE conditions were investigated to achieve the best resolution of the ESA and OXA enantiomers. The optimum background CZE electrolyte was found to consist of borate buffer (pH=9) containing 20% methanol (v/v) and 2.5% gamma-CD (w/v). Maximum resolution of ESA and OXA enantiomers was achieved using a capillary temperature of 15 degrees C and applied voltage of 30 kV. The applicability of the LC-MS and CZE methods was demonstrated successfully on the enantiomeric analysis of metolachlor and its metabolites in samples from a soil and water degradation study that was set up to probe the stereoselectivity of metolachlor biodegradation. These techniques allow the enantiomeric ratios of the target analytes to be followed over time during the degradation process and thus will prove useful in determining the role of chirality in pesticide degradation and metabolite formation. 相似文献
74.
Aldaya MM Lors C Salmon S Ponge JF 《Environmental pollution (Barking, Essex : 1987)》2006,140(1):173-180
We measured the short-term (100 min) avoidance of a soil heavily polluted by hydrocarbons by the soil springtail Folsomia candida, at six rates of dilution in a control, unpolluted soil. We compared the results with those of long-term (40-day) population tests. Five strains were compared, of varying geographical and ecological origin. When pure, the polluted soil was lethal in the long-term and avoided in the short-term by all strains. Avoidance tests, but not population tests, were able to discriminate between strains. Avoidance thresholds differed among strains. Two ecological consequences of the results were discussed: (i) toxic compounds may kill soil animals or deprive them from food, resulting in death of populations, (ii) pollution spots can be locally deprived of fauna because of escape movements of soil animals. Advantages and limitations of the method have been listed, together with proposals for their wider use in soil ecology and ecotoxicology. 相似文献
75.
Jennifer Butters Robert E. Mann Christine M. Wickens Paul Boase 《Journal of Safety Research》2012,43(5-6):405-411
IntroductionDriving safety, impaired driving, and legislation to address these concerns remain important issues. It is imperative countermeasures be targeted toward the most appropriate groups. This paper explores the potential relationship between gender and driving attitudes toward safety issues and impaired-driving countermeasures.MethodThe data are from the 2007 Impaired Driving Survey commissioned by Transport Canada and Mothers Against Drunk Driving (MADD) Canada. The survey is a, stratified by region, telephone survey of 1,514 Canadian drivers 18 years of age and older with a valid driver's license who had driven within the past 30 days.ResultsThe findings illustrate a consistent impact of gender on these issues. Other variables were also identified as relevant factors although less consistently. Current findings suggest that strategies for building support for interventions, or for changing risk perception/concern for risky driving behaviors should be tailored by gender to maximize the potential for behavior change.ImpactThis information may assist program and policy developers through the identification of more or less receptive target groups. Future research directions are also presented. 相似文献
76.
77.
78.
Eliecer Díaz Christine Güldenzoph Markus Molis Christopher McQuaid Martin Wahl 《Marine Biology》2006,149(6):1301-1311
Variabilities in the responses of several South African red and green macroalgae to direct grazing and the responses of one green alga to cues from grazers were tested. We used two feeding experiments: (1) testing the induced responses of three red and one green algae to direct grazing by mesograzers and (2) a multi-treatment experiment, in which the direct and indirect effects of one macrograzer species on the green alga Codium platylobium were assessed. Consumption rates were assessed in feeding assays with intact algal pieces and with agar pellets containing non-polar extracts of the test algae. Defensive responses were induced for intact pieces of Galaxaura diessingiana, but were not induced in pellets, suggesting either morphological defence or chemical defence using polar compounds other than polyphenols. In contrast, exposure to grazing stimulated consumption of Gracilaria capensis and Hypnea spicifera by another grazing species. In the multi-treatment experiment, waterborne cues from both grazing and non-grazing snails induced defensive algal traits in C. platylobium. We suggest that inducible defences among macroalgae are not restricted to brown algae, but that both the responses of algae to grazers and of grazers to the defences of macroalgae are intrinsically variable and complex. 相似文献
79.
Christine Errard Abraham Hefetz Pierre Jaisson 《Behavioral ecology and sociobiology》2006,59(3):353-363
To investigate the role of template plasticity in shaping nest-mate recognition processes in ants, we constructed experimental
mixed-species groups of Manica rubida with either Myrmica rubra, Tetramorium bicarinatum or Formica selysi. Selecting Ma. rubida as the focal species, we observed the behaviour within mixed-species groups and the transfer rates of cuticular hydrocarbons
(CHC) onto the focal ants, and we also tested the aggression of the focal species reared either alone or in association with
each of the three different species. We show that Ma. rubida workers were always amicable towards their mixed group members, as towards members of the respective parental colonies, irrespective
of the associated species. They did, however, express different levels of aggression towards single-species groups of the
other species tested, depending on the species with which they were reared. The study suggests that similarity in CHC profiles
in two species leads to a narrow template in mixed groups, while dissimilarity is followed by lower levels of aggression (a
broader template), at least against species with similar CHC compound compositions (i.e. both a broader template in the focal
ants and familiarity with the compound groups of the tested individuals operate together). This refutes the hypothesis that
ants reared in mixed-species groups are systematically more tolerant. It also demonstrates that heterospecific information
is not treated equally during development. We suggest that post-imaginal learning, template reforming and decision making
are more precisely tuned when the two species' chemical complexes are similar. 相似文献
80.
C. Magdalena Wolf Brad Griffith Christine Reed Stanley A. Temple 《Conservation biology》1996,10(4):1142-1154
In 1993 we conducted a follow-up study of the 1987 survey by Griffith et al. (1989) of 421 avian and mammalian translocation programs in North America, Australia, and New Zealand to reassess the programs' status and the biological and methodological factors associated with success. Our survey response rate was 81%. Approximately 38% of usable programs in 1993 reported a change in outcome from 1987 (e.g., a translocated population was "declining" but now is "self-sustaining"), but the difference between the overall success rates was not statistically significant (66% in 1987 and 67% in 1993). Since 1987, an increase was observed in the median number of animals translocated per program (31.5 to 50.5), median duration of releases (2 to 3 years), and proportion of programs releasing more than 30 animals (46% to 68%). Multiple logistic regression analyses indicated that release into the core of the historical range, good-to-excellent habitat quality, native game species, greater numbers of released animals, and an omnivorous diet were positively associated with translocation success. Moreover, our results indicate that translocated birds were less successful at establishing self-sustaining populations than translocated mammals. Our findings, using comparable logistic analyses, generally corroborate the results of Grifftth et al. (1989). Variables not found to be significantly correlated with translocation success include species' reproductive potential (number of offspring and first age of reproduction), number and duration of the releases, and source of the translocated animals (wild-caught versus captive-reared). 相似文献