Interpreting the scientific literature. Differences in the scientific and lay communities.

That the lay public can react differently to the scientific literature than does the scientific community was dramatically demonstrated recently in the context of genetically manipulated organisms. The journal Nature, a high-profile journal with a reputation in both the lay and scientific communities for quality, includes, along with full-length reports, a section called “Scientific Correspondence,” articles that are preliminary in nature. On May 20, 1999, a scientific correspondence appeared by John E. Losey, Linda S. Rayor, and Maureen E. Carter, titled “Transgenic pollen harms monarch larvae.” This short paper, less than a page in length and accompanied by only a single two-part figure, reported the results of a laboratory study in which pollen from corn (Zea mays) plants containing genetic material from Bacillus thuringiensis (Bt) was applied to leaves of milkweed (Asclepias curassavica) and administered to 25 larvae of the monarch butterfly (Danaus plexippus). Survival, weight gain, and proportion of leaf area consumed by larvae consuming untreated milkweed leaves were observed after 4 d and compared with that of larvae consuming milkweed leaves treated with corn pollen from an “unrelated, untransformed hybrid.” These authors reported that survival, consumption rate, and weight gain were lowest on foliage treated with Bt pollen. These authors then suggested that their results had “potentially profound implications for the conservation of monarch butterflies” due to the fact that milkweed plants, exclusive hosts for monarch larvae, can frequently be found in the midwestern United States around the perimeters of corn fields and thus, depending upon timing, “may be within range of corn pollen deposition” (Losey et al., 1999). To some extent, the findings by Losey et al. (1999) were not particularly novel; the Bt endotoxin gene with which Bt corn had been transformed was known to act specifically against lepidopterous larvae. The target species for these corn events is the European corn borer (Ostrinia nubilalis; Lepidoptera: Pyralidae). Previous reports in the literature of the toxic effects of CryIA(C) protein on nontarget Lepidoptera preceded the Losey et al. (1999) report; for example, Sims (1995) reported on the effect of B. thuringiensis var kurstaki [CryIa(C)] protein expressed in transgenic cotton on the tobacco hornworm (Manduca sexta). According to Charles Benbrook, a consultant to environmental groups and former associate of the Board on Agriculture of the National Academy of Sciences, “The report had nothing unexpected to those who have studied Bt and Lepidoptera” (Moffat, 2000a). However, it could be argued that the study demonstrated a need to consider more seriously the contributions made by corn pollen in distributing endotoxin beyond a corn plant. Reaction to the Losey et al. (1999) report in the scientific literature was swift and on balance critical. In the June 3, 1999, issue of Nature, John E. Beringer, chairman of the United Kingdom Advisory Committee on Releases to the Environment, published a letter in the “Correspondence” section criticizing the Losey et al. (1999) article on methodological grounds and restating its “preliminary rather than definitive” nature. Beringer (1999) specifically pointed out that the experiment lacked a critical control treatment—i.e. milkweed leaves treated with pollen from the same variety that had been transformed to generate the Bt corn. Although not specifically stated by Beringer, this omission is of importance at least in part because, according to Losey et al. (1999), the presence of untransformed, unrelated pollen on foliage reduced consumption rates significantly. Beringer (1999) also pointed out that the authors had not done a dilution study to determine the level of corn pollen contamination that would, under field conditions, affect larval growth and survival. With respect to the study, this author stated “Of course it is desirable to point out the potential harm that may arise from pollen dispersal. . . but the data reported by Losey et al. do not directly pertain to this issue. . . . Preliminary observations should not be overinterpreted. Regrettably, most reporting of the communication has almost entirely ignored the need for such caution.” Another response to the Losey et al. (1999) report appeared in the September 1999 issue of Nature Biotechnology and was authored by A.M. Shelton and R.T. Roush. Its tone was suggested by its title: “False reports and the ears of men.” Shelton and Roush (1999) cited a previous (but unpublished) field study examining Bt corn pollen deposition on milkweed plants in and around corn fields that failed to document significant impacts on monarch larvae. About the Losey et al. (1999) paper, they wrote: “We believe that few entomologists or weed scientists familiar with butterflies or corn production (and the control of milkweed) give credence to the Nature article, but the public and its policy makers have reacted in a