Biology 423 Winter 2013 Lecture 07

Indirect interactions since wolf reintroduction

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Unformatted text preview: interactions Indirect interactions occur when one species has an effect on another through an intermediate species. Indirect interactions • Since wolf reintroduction, willows grow better near rivers. Indirect interactions • Elk eat willow saplings. • Wolves make elk wary near rivers. Indirect interactions Do wolves enhance willow survivorship? area (Xe) area (Xc) Parameter, by trophic Mean Mean Indirect interactions level N 2140 MARK HEBBLEWHITE ET AL. Predator H1: Wolves enhancekilled/d Total elk willow survivorship 13 0.07 0.01 0.2 Predicted response SE SE 0.03 TABLE 1. Natural experimental comparison of the effects of partial wolf exclusion on tr Herbivore Park, Alberta, Canada. 2140 density (no. elk/km2) MARK HEBBLEWHITE ET 0.96 AL. Elk 15 9.35 0.38 0.17 0.89 0.06 0.62 0.06 Adult female elk survival 45 High-wolf Low-wolf 27.4 14.6 1.97 Calf:cow Natural experimental 14 TABLE 1. recruitment ratio (%) comparison of the effects of X1.58 wolf exclusion) on tr partial area (Xc area e) Fecal nitrogen (% of total 113 Pre...
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