Ground beetle species in heathland fragments in relation to survival, dispersal, and habitat preference.

Local numbers of ground beetle species of heathland appeared to be significantly associated with size of total area, whereas such relationships were not found for the total number of ground beetle species and eurytopic ground beetle species. Presence of species with low chances of immigration was highly associated with area. This is accordance with the "area per se" hypothesis for islands as far as extinction rates are concerned. The habitat diversity hypothesis and the random sampling hypothesis are of less importance for explaining this phenomenon. The importance of dispersal for presence and survival in fragmented habitats could be demonstrated. This result supports the founding hypothesis, under which founding of new populations is considered the main effect of dispersal. The frequency of heathland species with low powers of dispersal in habitats smaller than 10 ha was 76% lower on average than in areas larger than 100 ha. For heathland species with high powers of dispersal this frequency was only 22% lower on average. The period of isolation of the habitats studied, 26-113 years, appeared to be too long to persist for many populations of heathland species with low powers of dispersal.

[Measurement of dentists' treatment conceptions]. / Meting van de behandelconcepties van tandartsen.

It was hypothesized that dentists have different conceptions of treatment. A distinction was made between a relational dimension with extremes a communicative and a directive conception and a dental dimension with extremes a restorative and a preventive conception. For the measurement of the conceptions a questionnaire of fourty-three items was constructed. The questionnaire was administered to 149 dentists in The Netherlands. Using factor analysis eleven items were selected for the relational dimension and also eleven items for the dental dimension. Cronbach's coefficient alpha is .75 for the relational dimension and .78 for the dental dimension; the correlation of the two dimensions is .21. Therefore, the conceptions can be measured using the questionnaire. The conception of the dentists is in general communicative; the variation between the restorative and preventive conceptions is rather large.