Wednesday, May 28, 2008 - 4:00 PM
488

Stonefly life-history differences between runoff-dominated and spring-fed streams: A reciprocal transplant experiment

Asako M. Yamamuro and David A. Lytle. Department of Zoology, Oregon State University, 3029 Cordley Hall, Corvallis, OR 97331

Understanding whether life-history traits are constrained or plastic is important when forecasting resilience following drastic environmental changes, such as anthropogenic alterations to flow regime.  To explore this, we conducted a reciprocal transplant experiment between a runoff-dominated and a spring-fed tributary to the McKenzie River, OR.  We expected insects in the runoff-dominated stream to emerge prior to summer low flows to avoid degraded in-stream conditions.  In contrast, we expected insects inhabiting the spring-fed stream, with little seasonal variation in flow, to continue emerging throughout the summer.  Yoraperla nigrisoma (Peltoperlidae) larvae were reciprocally transplanted in replicated enclosures in both stream types.  Of the insects that emerged, more were of spring-fed than runoff-dominated origin (p<0.005), indicating a constrained natal stream effect.  Of the insects originating from the spring-fed stream, those transplanted to the runoff-dominated stream had larger head widths than those placed in the natal spring-fed stream (p<0.05).  This difference was due to a greater proportion of (69%) females, which are larger than males (p<0.05), emerging from the runoff-dominated stream compared to the proportion of females emerging from the spring-fed stream (18%).  Life-history differences between natal streams and between transplanted and native treatments indicate some degree of both genetic constraint and phenotypic plasticity.


Web Page: reciprocal transplant experiment, stonefly, flow regime

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