Polydomy enhances foraging performance in ant colonies.

Collective foraging confers benefits in terms of reduced predation risk and access to social information, but it heightens local competition when resources are limited. In social insects, resource limitation has been suggested as a possible cause for the typical decrease in per capita productivity observed with increasing colony size, a phenomenon known as Michener's paradox. Polydomy (distribution of a colony's brood and workers across multiple nests) is believed to help circumvent this paradox through its positive effect on foraging efficiency, but there is still little supporting evidence for this hypothesis. Here, we show experimentally that polydomy enhances the foraging performance of food-deprived Temnothorax nylanderi ant colonies via several mechanisms. First, polydomy influences task allocation within colonies, resulting in faster retrieval of protein resources. Second, communication between sister nests reduces search times for far away resources. Third, colonies move queens, brood and workers across available nest sites in response to spatial heterogeneities in protein and carbohydrate resources. This suggests that polydomy represents a flexible mechanism for space occupancy, helping ant colonies adjust to the environment.

Reference accuracy in peer-reviewed pediatric orthopaedic literature.

BACKGROUND: Reference accuracy of articles published in the biomedical literature is determined by the presence of citation and quotation errors. A recent review demonstrated that the median citation error rate per biomedical journal was 39%, and the median quotation error rate per journal was 20%. Reference accuracy in pediatric orthopaedic articles has not been previously reported, to our knowledge. METHODS: Two hundred references from twenty articles published in four peer-reviewed orthopaedic journals were randomly selected for assessment of citation and quotation accuracy. Full-text copies of all original references were obtained by interlibrary loan methods and reviewed directly to establish citation accuracy. The presence of citation errors was determined by a single investigator. The relevance of citation errors was determined by assessing the ease of reference retrieval through PubMed. Quotation accuracy was determined by two examiners who reviewed each of the twenty articles and 200 references to compare the claims made for the references in the article against the data and opinions expressed in the actual reference. RESULTS: The total citation error rate across all of the journals was 26% (fifty-one of 200 references) with a 95% confidence interval of 16.5% to 37.3%. The median citation error rate per journal was 27% (range, 10% to 38%). Although citation errors were common, most were of minimal significance, as 196 of the 200 references could be retrieved with ease from PubMed. The total quotation error rate across all of the articles was 38% (152 of 398 reference citations) with a 95% confidence interval of 30.1% to 47.0%. The median quotation error rate per journal was 38% (range, 28% to 46%). CONCLUSIONS: Citation and quotation errors are common in the pediatric orthopaedic literature. Reference accuracy continues to be a substantial problem in the biomedical literature despite recent technological advances such as online databases, easily accessible search engines, and widely available bibliographic software.

HLA antigens in grass pollinosis.

48 patients with grass pollinosis and strongly positive skin tests to crude timothy pollen extract, as well as the relatives of 11 of the, were typed for 26 HLA antigens of the A and B loci. No significant alteration in the frequencies of any particular antigen was observed, except for an increase of HLA-A1 and B8 in patients with multiple manifestations of reaginic disease. In the 11 families investigated, susceptibility to grass pollinosis and IgE levels did not appear to be linked to HLA haplotypes. Preliminary studies with anti-lymphocyte B sera did not reveal any significant alteration in the frequency of positive reactions, using enriched population of B lymphocytes from 16 patients.