Dietary overlap and coexistence of chironomid larvae in a detritus-based stream

Of the seven orders of macroinvertebrates that make up the DuffinCreek riffle community, the Chironomidae were the dominant taxonmaking up, numerically, 25.8–53.7% of the total fauna. Cricotopus sp., ?Rheosmittia sp. and a species from the Eukiefferiella brehmi group predominated whereas Parametriocnemus sp., Thienemanniella sp., Tanytarsussp., and Rheotanytarsus sp., were common. The three leastabundant chironomids were Ablabesmyia sp., Microtendipes sp. and a species from the Stempellinamontivaga group. The coexistence of a variety of life stages ofeach species throughout the year indicates a high degree oftemporal overlap. The major food type both in the environment andin the larval guts was detritus. Dietary overlap indices indicatedalmost complete overlap (0.89–0.99) and a convergence of diets –the highest values were generated from hyporheic feeding datacompared with rock surface grazing data. Niche breadth valuesindicated a predominance of generalist feeding throughout most ofthe year (0.62–0.99).