Habitat shift and geographical variation in North American tanagers (Thraupinae: Piranga)

Summary Relationships of habitat structure among North American tanagers were studied in large areas of their breeding ranges in the USA. In the large areas sampled, the four species differ significantly in multivariate scores of habitat structure. In Scarlet and Summer Tanagers (for which the most data was collected) there is intraspecific geographical variation in habitat features. Variation in habitats of Summer Tanagers is more pronounced than that of Scarlet Tanagers, and is related to changes of macrohabitats in low elevations from oak-pine and mixed woods in the southeast to riparian vegetation in the dry southwest. In the southeast these two species often breed in the same localities, and establish territories next to each other. In six localities in which I found both of them, the difference between the two species in habitat structure is significantly greater than in allopatric areas in the southeast. These results, and those of another study on song variation and behavioral responses to song suggest that coexistence of Scarlet and Summer Tanagers in sympatry can be explained both by partial habitat shift, and by interspecific aggressive division of space. It is concluded that quantitative sampling of habitats in large areas of distributional ranges of species is needed before any conclusions on species-specific preference and interspecific competition can be made.     

Rotavirus electropherotypes in Malaysian children.

A 12-month study was carried out on the molecular epidemiology of rotavirus in urban and suburban Malaysian children. Analysis of faecal samples from 973 hospitalized diarrhoeic children by polyacrylamide gel electrophoresis detected 268 rotaviruses (28%). All isolates were group A rotaviruses, which produced 22 electropherotypes: 16 (91.5%) with long RNA migration patterns and 6 (8.5%) with short patterns. One of the long-pattern electropherotypes was the predominant strain (71.1% of the total electropherotypes) isolated during this study. Although 3 other strains were detected sporadically over the study period, 16 others were present only during the first 7 months and 2 others were confined to the last 5 months. Long- and short-pattern electropherotypes were found to co-circulate extensively. There was a significant association of short-pattern electropherotypes with infection in older children. In addition, the prevalence of vomiting and mean duration of diarrhoea were significantly associated with different electropherotypes.