Document: CHR-3-51-22

Source-sink population dynamics of a Rocky Mountain mayfly: Estimating patch quality and dispersal.

CAUDILL, C.C.* ^1,2 and B.L.PECKARSKY ^1,2

Cornell University, Ithaca, NY 14853 ¹
Rocky Mountain Biological Laboratory, Crested Butte, CO 81224 ²

Abstract:
Predictions of metapopulation models depend critically on the degree of dispersal among patches and patch size or "quality," and successful management of spatially structured populations requires an understanding of the relationship between these parameters. However, few estimates of these parameters are available for natural populations, and thus, which types of metapopulations (e.g. mainland-island, source-sink, etc.) are common is unknown. To quantify the relative roles of patch quality and dispersal in a metapopulation, we have estimated larval survival, adult production, and recruitment of the mayfly Callibaetis ferrugineus hageni in a series of twelve beaver ponds in the upper East River valley of Colorado. The ponds vary in the presence/absence of trout predators, which covaries with depth--fishless ponds tend to be deeper in this system. Larval survival was markedly higher and adult production was approximately an order of magnitude greater in "source" ponds without trout than "sink" ponds with trout. Larval survival may be related to fish predation and/or low oxygen during winter in shallow ponds. Subsequent recruitment did not differ between pond types as estimated by the density of ovipositing females and suggests that many females disperse from their natal habitat to oviposit, that females do not selectively avoid low quality habitat during oviposition, and that sinks are not recruitment limited. Thus, this population appears to follow a patchy source-sink dynamic where exchange among patches is high and patches differ markedly in their quality. This type of dynamic may be common in spatially structured populations where growth and dispersal occur in separate life-history stages. Identifying and conserving source patches is critical to managing populations that follow a source-sink metapopulation dynamic.

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This abstract is being presented at: 10:15 AM in session:
Oral Session #55: Invertebrates in Streams: Foodwebs.