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Abstract

Patterns in the community structure of darkling beetle (9 Eleodes spp., Coleoptera: Tenebrionidae) assemblages in the shortgrass steppe of north central Colorado were monitored by live pitfall trapping for 4 summers. There were significant correlations among weather (temperature and precipitation), species richness, and number of individuals per species captured; effects from weather conditions also displayed 1-month and 1-yr delayed effects. Population densities of 2 eleodid species were monitored by mark-recapture methods. Densities of these species varied relatively little among years and sites, although density was correlated with temperature and precipitation. Abiotic influences on both density and richness differed between 2 macrohabitat types (shortgrass upland, shrub floodplain). The 4 largest species were most abundant in the floodplain, whereas the smallest species was most common in the upland. Affinities with cactus and shrub microhabitats (and an avoidance of bare soil) were evident, although a preference for shaded microhabitats was not detected. These results do not conform well to previous explanations of why darkling beetle assemblages are spatially and temporally heterogeneous, which primarily focused on predation and thermoregulation. Therefore, an alternative mechanism concerning scale-dependent uses of heterogeneity and mobility is proposed to account for eleodid community patterns.

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