Tests for character displacement.

Character displacement is an important concept in ecology which has been surrounded by controversy due largely to a lack of clearly stated hypotheses and statistical tests. Existing tests implicity assume random species sizes estimated without error--a random-effects model. We introduce the log-uniform distribution for species sizes and show that it has properties of direct relevance to character displacement. We present tests which assume uniform and log-normal species sizes and have the log-uniform distribution as an alternative. The tests have low power for sample sizes typically encountered in ecology. The effect of estimating species sizes is small. The results exemplify the shortcomings of the traditional random-effects model for species sizes.

Tests for deletion.

It has been suggested in the ecological literature that species may be excluded (or "deleted") from an environment because they do not differ sufficiently from other species in the environment. We develop tests of various deletion hypotheses based on the assumption of a random distribution of species sizes. The results provide information on the behavior of quantities of interest to ecologists studying this phenomenon, namely contiguous ratios, and allow us to gauge the extent of deletion required before we can be confident of detecting it. The results indicate that this random-effects approach leads to tests which have low power for ecological applications but may be more useful in fields which permit larger sample sizes.

Sampling and analysis techniques used in a blood lead survey of 1241 children in Port Pirie, South Australia.

Methods are described for taking finger-prick blood samples and for analyzing these samples for lead. Quality-control techniques and procedures for the validation of all results are described. Results of a survey of 1241 children are given and results for 149 venous samples are compared with results for the corresponding finger-prick samples. This finger-prick sampling method evidently is suitable for use in screening large numbers of children.