Interactions of the invasive New Zealand Mudsnail (Potamopyrgus antipodarum) and native macroinvertebrates in Polecat Creek, WY

Wise, Kara
In Polecat Creek, WY, located within the Greater Yellowstone Ecosystem, the invasive New Zealand mudsnail (Potamopyrgus antipodarum) was once recorded at densities of over 500,000 individuals/m2. In recent years, the biomass of P. antipodarum in Polecat Creek has decreased, suggesting a "boom and bust" pattern in population density. The population reached its highest density in 2000-2001, but by 2011, it had decreased by 93%. Native net spinning caddisflies (Hydropsyche spp.) have increased significantly in biomass from 2001-2011, suggesting that the native macroinvertebrates may have increased due to release from suppression by P. antipodarum. I collected macroinvertebrate core samples in Polecat Creek to measure the density of P. antipodarum and native macroinvertebrates. I also conducted a field experiment to assess the possible mechanisms by which P. antipodarum may have suppressed Hydropsyche caddisfly larvae. I placed Hydropsyche larvae on wooden tiles within experimental chambers in Polecat Creek to colonize and build nets, then added boom and bust densities of P. antipodarum to the experimental chambers. Preliminary results show no significant difference between the number of Hydropsyche nets before the addition of P. antipodarum to chambers and after the addition of P. antipodarum at boom or bust densities in chambers. These results suggest the invasive P. antipodarum do not actively destroy caddisfly nets, but may interfere with feeding by gathering on nets, therefore reducing the amount of food Hydropsyche larvae can catch.
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