Evaluating the post-release efficacy of invasive plant biocontrol by insects: a comprehensive approach

We propose a comprehensive program to evaluate the post-release phase of biocontrol programs that use insect herbivores to control invasive plant species. We argue that any release should be done in randomized release and non-release sites and should be followed up by well-replicated sampling and experimental protocols that evaluate the degree of success or failure. These follow-up studies should include landscape scale monitoring across relevant habitat gradients of (1) the abundance of the biocontrol agent, (2) the impact of the biocontrol agent on the target plant species, (3) the potential for non-target effects, and (4) the response of native species and communities to a reduction in the invasive species. We also argue that (5) experimental reductions of the biocontrol agent are required to eliminate the chance that the putative impact of the biocontrol agent is not confounded with other causes. Finally, we describe six scenarios, informed largely by a community ecology perspective, in which a biocontrol agent may decrease the abundance or vigor of the target plant species but not lead to successful control where native communities re-establish. We classify these failure scenarios as either direct or indirect effects of the invasive plant species: Native Source Limitation, Static Competitive Hierarchies, Novel Weapons, Trophic Shifts, Invasive Engineering and Associated Invasives. Overall, we argue that well replicated and landscape-scale post release monitoring programs are required not only to evaluate critically the degree of success and failure of biocontrol programs worldwide but also to provide insights into improving future biocontrol efforts. Handling Editor: Heikki Hokkanen.     

Fear of crime among Arab Americans in a culture of fear

As the minority group frequently at the centre of public fear in the post-9/11 era, Arab Americans’ own sentiment toward, and concerns with, crime, has eluded scholarly attention. This study investigated their fear of crime net of five empirically validated fear of crime theoretical models. Face-to-face interviews with a random sample of Arab and non-Arab households in Metro-Detroit, Michigan indicated that net of all controls, Arab Americans experienced significantly higher levels of fear concerning both general and bias crimes than non-Arab Americans. The greater fear among Arab Americans calls for policy and practice change, and moving from perceiving Arab Americans as a major “source” of fear, to “carriers” of fear who are in need of more attention, care, and assistance.     

Vertical transmission in feather mites: insights into its adaptive value

1. The consequences of symbiont transmission strategies are better understood than their adaptive causes. 2. Feather mites are permanent ectosymbionts of birds assumed to be transmitted mainly vertically from parents to offspring. The transmission of Proctophyllodes doleophyes Gaud (Astigmata, Proctophyllodidae) was studied in two European populations of pied flycatchers, Ficedula hypoleuca Pallas (Passeriformes, Muscicapidae). 3. The vertical transmission of this mite species is demonstrated here with an acaricide experiment. This study also compared (for two distant populations during 4 years) patterns in reductions in mite intensity in adult birds, from egg incubation to chick‐rearing periods, with the predictions of three hypotheses on how host survival prospects and mite intraspecific competition might drive feather mites' transmission strategy. 4. The results are in agreement with previous studies and show that feather mites transmit massively from parents to chicks. 5. The magnitude of the transmission was closer to that predicted by the hypothesis based on intraspecific competition, while a bet‐hedging strategy is also partially supported.     

Functional consequence of variation in melanoma antigen expression

Summary Melanoma cells have been shown to express melanoma-associated antigens and, in many cases, the histocompatibility antigen, HLA-DR. We questioned whether the expression of these antigens was quantitatively altered during the serial passage of melanoma cells in culture. Therefore, we measured the binding of monoclonal antibodies specific for a melanoma-specific antigen and the HLA-DR antigen to melanoma cells from serial passages. Three cell lines were studied. We found that although both the melanoma-associated antigen and the HLA-DR antigen were qualitatively conserved, significant quantitative differences were seen. To study the functional consequences of these differences, we used fluorescence-activated cell sorting to create DR-enriched and DR-depleted populations from a single melanoma cell line heterogeneous for DR expression. We found that the proliferation of allogeneic T cells (measured by the ³H-TdR uptake) cultured with the DR-enriched and -depleted melanoma cell populations was directly related to the amount of the HLA-DR antigen expressed. These results indicate that in performance of experiments using melanoma cell lines quantitative assessment of antigenic expression is important, particularly if the function of a specific antigen is under examination. Further, our data clearly identify the HLA-DR antigen on melanoma cells as a participant in allogeneic lymphocyte stimulation. Abbreviations used are: FACS, fluorescence activated cell sorter; FITC, fluorescein isothocyante; ³H-TdR, tritiated thymidine