Factors affecting the community ecology of predacious diving beetles (Coleoptera: Dytiscidae) in boreal and prairie ponds across southern Manitoba
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Bottle-traps and volume-sampling were effective techniques for collecting dytiscids. A total of 17 060 dytiscids were collected in two years among 30 ponds, using both sampling methods. Conclusions about the factors that organize dytiscid communities were similar, based on the results obtained from both methods of sampling. However, bottle-traps collected elusive, rare, or large species effectively whereas volume-sampling was better at collecting small species. Recommendations for the sampling regimes of future studies are provided. A primary objective of this study was to relate and rank the environmental variables of boreal and prairie ponds that influence dytiscid diversity. This objective was accomplished by measuring various environmental variables for each pond including pH, conductivity, chlorophyll a density, pond permanence, pond area, macrophyte density, emergent vegetation density, and presence of fish and tiger salamanders. The environmental profiles of ponds were compared with their respective dytiscid communities. Multivariate analysis was used to determine the affinities of pond communities and species to the respective environmental variables. Environmental variables important for discriminating between boreal and prairie ponds included macrophyte diversity, pH, water conductivity, chlorophyll a density, and pond permanence. Among these variables, macrophyte diversity was considered a particularly good indicator of dytiscid communities...