Natural selection by avian predators on size and colour of a freshwater snail (Pomacea flagellata)

Wendy L. Reed, Fredric J. Janzen

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42 Scopus citations


We identify two avian predators of the Neotropical apple snail, Pomacea flagellata, and estimate the strength, direction and form of multivariate natural selection by these predators on size and colour of snail shells. Limpkins are tactile predators and act as agents of disruptive selection on snail size, selecting average-sized snails disproportionately more often than small or large snails (γ = 0.39, SE = 0.08). In addition, we were able to identify variation in handling behaviours and snail size selection among individual limpkins. Individual limpkins showed preferences for snails of different sizes and punctured the snail shells opposite the aperture mainly when handling large snails. Snail kites are visual predators and seem to be agents of directional selection against lighter coloured snails (β' = 0.66, SE = 0.33). The ecological interaction between the apple snail and its predators provides a powerful system to further explore the role of predation in determining evolutionary changes in snail behaviour, morphology and life history.

Original languageEnglish (US)
Pages (from-to)331-342
Number of pages12
JournalBiological Journal of the Linnean Society
Issue number3
StatePublished - Jul 1999
Externally publishedYes

Bibliographical note

Funding Information:
We are grateful to the Organization for Tropical Studies for making this project possible, and to Steve Shuster and BOP group members for making constructive comments on early drafts of the manuscript. We would like to extend special thanks to Brian Wiegmann for his help with the collection and synthesis of material needed for completion of this project. This project could not have been completed without his help. This research was completed with partial support from the University of Chicago, an Iowa State University Research Grant, and National Science Foundation grant DEB-9629529 to FJJ. This is Journal paper No. J-18160 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA. Project No. 3369, supported by the Hatch Act and State of Iowa Funds.


  • Disruptive selection
  • Limpkin
  • Snail kite


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