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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Life Histories
DOES LOCAL RECRUITMENT OF THE MAYFLY BAETIS BICAUDATUS DETERMINE LOCAL LARVAL ABUNDANCE?
A.C. Encalada1,2 and B.L. Peckarsky1,2. 1Department of Entomology, Cornell University, Ithaca, NY 14850, 2Rocky Mountain Biological Laboratory, Gothic, CO 81224
We conducted surveys in high-altitude streams in western Colorado to determine patterns of variation in recruitment (oviposition) of the mayfly Baetis bicaudatus and consequences for subsequent larval densities. During summers 1999 - 2001, we counted all available oviposition sites (protruding rocks), the number of Baetis egg masses (recruitment), and sampled larvae in 30-m reaches of 6 - 21 streams. We found that streams with more oviposition sites and higher recruitment in one year were also good sites the next year. If larval densities were recruitment-limited at the local scale, we expected positive relationships between local oviposition and local larval density, and the highest deviation from expected relationships to occur in later larval stages due to larval mobility. Interestingly, we found a weak, but significant positive correlation between local densities of egg masses (1999) and local densities of mid - late stage Baetis larvae (2000). These data demonstrate a potential for recruitment limitation of this species. However, we speculate that larval densities may be recruitment limited at a regional rather than local scale. In this case we expect sites with more upstream habitat (greater source pool of colonists) to show the greatest deviation from expected relationships between local oviposition and local larval densities.
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