HR: 09:30h
AN: NB51B-05    [Abstracts]
TI: Habitat-specific Tradeoffs Between Risk of Flow-induced Dislodgment and Fish Predation Affect Shell Morphologies of Potamopyrgus antipodarum in New Zealand
AU: * Holomuzki, J R
EM: holomuzki.3@osu.edu
AF: The Ohio State University, Department of Evolution, Ecology, and Organismal Biology 1680 University Drive, Mansfield, OH 44906 United States
AU: Biggs, B J
EM: b.biggs@niwa.co.nz
AF: National Institute of Water and Atmospheric Research, P.O. Box 8602, Christchurch, New Zealand
AB: Smooth and spiny shell-morphs exist in populations of the mudsnail Potamopyrgus antipodarum in New Zealand streams and lakes. We estimated the relative frequencies of smooth and spiny shell-morphs from 11 rivers and 9 lakes on the South Island and used stepwise regression to identify environmental variables that affected shell-morph frequencies. Habitat (stream or lake) explained 57% of the variation in morph frequency. Nearly 70% of snails in streams were smooth-shelled, whereas >80% of snails in lakes were spiny. Results from flow tank experiments showed that spines collected seston (sloughing algae and leaf matter) at current speeds <40 cm/s, making spiny-morphs more prone to flow-induced dislodgment than smooth-morphs. Moreover, individuals with longer spines collected more seston, and hence were more susceptible to dislodgment, than those with shorter ones. However, an advantage of spines was lower predation rates by common bullies (Gobiomorphus cotidianus), a widespread benthic fish in New Zealand streams and lakes. All snails egested by bullies were dead, suggesting common bullies may help regulate mudsnail populations in nature. Our results suggest tradeoffs between susceptibility to flow-induced dislodgment and fish predation affect habitat-specific frequencies of shell morphologies for this snail.
DE: 9810 New fields (not classifiable under other headings)
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly