THE EFFECT OF CERTAIN SOIL TREATMENTS ON DIDYMELLA STEM ROT OF TOMATOES PART I. GLASSHOUSE EXPERIMENTS

When tomatoes were planted in steamed soil inoculated with spores of Didymella lycopersici Kleb., a large proportion became infected, but very few became infected in unsteamed soil similarly inoculated. In soil treated with formalin and subsequently inoculated the number of diseased plants was about half that in steamed soil. Reinfecting steamed soil with soil micro-organisms before inoculation with D. lycopersici reduced the amount of disease. Covering steamed soil with a layer of maiden loam filtered out a large proportion of D. lycopersici spores applied in water suspension and reduced the amount of disease. Addition of stable manure either before or after steaming did not affect the number of diseased plants. Steamed soil remained susceptible to infection by D. lycopersici for 4 months. D. lycopersici survived in a glasshouse soil over the winter, but the number of diseased plants was small. Cultivation may lessen the amount of disease by burying most of the infected surface layers of the soil. The peak of infection under glass occurred in May. The amount of disease and the yield were correlated, but with severe infection the yield varied with the time of infection and the distribution of diseased plants.     

Influences of two life‐history stages of the weevil,Larinus minutus,on its host plant Centaurea diffusa

1. We hypothesised that, for weed biological control, using species that feed as both adults and larvae would be advantageous. Here, we test the impacts of adult and larval feeding of Larinus minutus (Col.: Curculionidae), a successful biological control agent of diffuse knapweed, Centaurea diffusa (Asteraceae), in British Columbia, Canada. 2. At one site, the observations of the present study showed that the intensity of adult weevil feeding did not predict the level of larval attack. Experiments found no evidence for plant‐mediated competition between the life‐history stages. 3. At two sites and in two years, experimental manipulations of adult and/or larval feeding damage were conducted and plant performance measured. Neither antagonistic nor synergistic interactions occurred, but at each of the two sites a different life‐history stage was responsible for reduction in the number of seeds produced by the plants. 4. Although one of the two different feeding modes was redundant at each site, the ability of adults and larvae to reduce plant performance in different areas makes the species effective in a wider range of environments.     

Ophryocystis elektroscirrha sp. n., a Neogregarine Pathogen of the Monarch Butterfly Danaus plexippus (L.) and the Florida Queen Butterfly D. gilippus berenice Cramer1

SYNOPSIS. Naturally occurring populations of the monarch butterfly, Danaus plexippus (L.) and the Florida queen butterfly D. gilippus berenice Cramer were found infected with Ophryocystis elektroscirrha sp. n. This neogregarine pathogen infects the hypodermal tissue, remains in micronclear schizogony until after pupation of the host, and then rapidly completes morphogenesis in the tissue that becomes the scales of the adult butterfly. The adult thus carries the spores externally; no internal infection was detected. The pathogen is unique in the genus Ophryocystis because: other species have all been reported from the Malphigian tubules of Coleoptera; no pseudopodial attachments of schizonts to host tissue were seen; the merozoites were motile; the cystic membrane surrounding the zygote was tenuous, and the sporont developed with no apparent membrane other than the spore wall: and the spore wall appeared amber in transmitted light when morphogenesis was completed.     

Some aspects of the host:parasite relationships between adult blackflies (Diptera; Simuliidae) and larvae of the water-mite Sperchon setiger(Acari; Hydrachnellae) in a small chalk stream in southern England

SUMMARY. In Bere Stream three species of adult simuliids, S . ornatum, S. equinum and S. angustipes were parasitized by Sperchon setiger larvae. Trapped adult S. ornatum were more often parasitized than corresponding adults of S. equinum. The lower 95% confidence limits were used as an indication of the relative importance of the statistically significant differences and were high (10.4–33.6%). Laboratory experiments on the occupation of host pupae by pre-parasitic Sperchon setiger larvae also indicated that pupae of S. ornatum were more often occupied than S. equinum. This was confirmed by tests on the difference in percentage occupation of more than 4000 held-collected host pupae. In tests that indicated a significant difference in percentage parasitization between the sexes of the three host species, females were more often parasitized. However, the lower 95% confidence limits for the increase in percentage parasitization of females compared to males were low (0.9–10.2%). The majority of adult simuliids carried only one parasite. The mean number of larvae per trapped parasitized host was significantly greater for S. ornatum (2.69) than for S. equinum (1.77). There was no significant difference between the mean number of parasites carried by the sexes of S. ornatum for each year from 1975 through 1978 but females were significantly more heavily parasitized than males during 1979. The ventral neck region of all three host species is the main attachment site for Sperchon setiger larvae.
The morphology of the pupae of S. ornatum and S. equinum is related to differences in levels of percentage parasitization between these two species. It is suggested that pupal morphology may be the most important factor in the selection of host simuliids by Sperchon setiger larvae.     

Competition and macroevolution: the ghost of competition yet to come?

Competition theory is the focus of much debate among both neontologists and palaeontologists. This paper explores the expansion of competition theory into macroevolution, since this is the relevant context for palaeobiologists, and challenges the contention that microevolutionary processes are generally inappropriate to the interpretation of macroevolutionary pattern. We show that the term 'interspecific competition' is imprecise, since it conflates processes operating at various hierarchical levels, and recommend a terminological change in accordance with hierarchy theory. Finally, we reassess the role of competition and its absence in radiations. Since evolutionary novelties must be fixed at speciation, and speciation occurs in response to habitat destruction rather than the freeing of ecological space, we believe the role of competition to be minimal in both radiation and the generation of novelty.     

“WE CAME TO TALK WITH THE PEOPLE BEHIND THE DISEASE:” COMMUNICATION AND CONTROL IN MEDICAL EDUCATION

To explore the ways in which biomedical culture responds to the new curricular addition of communication skills training, we observed activities related to the communication skills training of a class of 70 first-year medical students in an Israeli medical school during 2002–3. In addition, focus groups were conducted with medical students (n = 210) during 1998–2001. A gap was found between the rhetoric of “patient-centered communication” and “empathy” and the traditional concerns of medical authority, efficiency, and scientism. Communication skills and empathy training were appropriated into medical socialization by being reconstructed as clinical competence. Findings are further discussed in the context of medical professionalism, Israeli culture, service acting and service roles, and organizational learning.