Aquatic insect community differences between runoff-dominated and spring-fed streams

Flow regimes can produce different community types, especially in systems with drastic differences in geology.  We studied streams of two different types of geology that either have seasonally variable hydrographs (runoff-dominated streams) or relatively constant hydrographs (spring-fed streams).  Knowledge of how community composition differs between streams with different flow regimes will provide insight into the relationship between stream biotic and abiotic factors.  Associations between life-history traits and stream type could provide a useful way to predict life-history traits of community members for a stream with a given flow regime.  We analyzed stonefly and mayfly assemblages and life-history traits (voltinism, development, emergence synchrony) in five runoff-dominated and five spring-fed tributaries of the McKenzie River, OR.  Differences were found in the plecopteran and ephemeropteran communities between runoff-dominated and spring-fed streams.  Runoff-dominated streams had higher abundances of Doroneuria and Calineuria (Perlidae), Kathroperla (Chloroperlidae), and Pteronarcys (Pteronarcyidae), while spring-fed streams had higher abundances of Yoraperla (Peltoperlidae).  The abundance of Ameletus (Ameletidae) was higher in runoff-dominated streams, while the abundance of Caudatella (Ephemerellidae) was higher in spring-fed streams.  Generally, density differences were found for particular taxa between the two stream types.