Biodiversity of aquatic insects in relation to temperate and tropical land use, and the life histories and microhabitat associations of lotic mayflies

Life history studies were conducted on commonly collected mayflies from Missouri Ozark streams. The microhabitat associations of selected mayflies then were determined. Lastly, biodiversity of the lotic community was examined in relation to land use, from both a temperate and tropical standpoint.; Based on multivariate analysis of mensural characters of Stenonema mediopunctatum (Ephemeroptera: Heptageniidae) nymphs, at least nine instars were present in the stream during the sampling period. The method of using a suite of ln-transformed body measurements was found to provide more resolution than using raw data or head capsule widths alone. Also, S. mediopunctatum was determined to be univoltine in these streams, as were C. hilaris and C. latipennis (Ephemeroptera: Caenidae), whereas Tricorythodes curvatus (Ephemeroptera: Tricorythidae) was found to be multivoltine.; When examining a suite of abiotic habitat variables in relation to presence or absence of particular mayfly species, it was determined that substratum, simple hydraulic, and complex hydraulic characters were important. However, multivariate analysis determined that a high degree of overlap in habitat association exists and the levels of importance varied interspecifically.; Aquatic macroinvertebrate biodiversity was examined in two Missouri Ozark streams in relation to adjacent land use. Diversity values in cleared/grazed areas were higher than in forested sites, possibly indicating an intermediate level of disturbance or that the level of disturbance was not sufficient to have deleterious effects. Also, all categories of functional feeding groups were present at both sites, indicating functional similarity between the two sites.; In a tropical setting, in southern Thailand, biodiversity of the aquatic macroinvertebrate community again was examined in relation to land use. The pattern of diversity levels was similar to that found in the temperate study, with the cleared areas having increased diversity. The aquatic communities of the two streams in the study were significantly different from each other, indicating that other abiotic and biotic factors also may have an influence on community structure.