, Volume 94, Issue 4, pp 496–502 | Cite as

Herbivore deme formation on individual trees: a test case

  • Neil S. Cobb
  • Thomas G. Whitham
Original Papers


We examined the deme-formation hypothesis, which states that sessile herbivores on long-lived hosts become locally adapted to the defensive phenotypes of individual trees. We showed a five-fold increase in resistance by individual pinyon pines (Pinus edulis) to the pinyon pine needle scale (Matsucoccus acalyptus). Although such variation could represent a significant selection pressure favoring deme formation, two lines of evidence led to rejection of the hypothesis. First, there were no significant differences in mortality among scale populations in a reciprocal transfer experiment. Second, a seven-year experiment showed that mortality of newly founded, incipient scale populations was similar to established scale populations. While our experiments fail to support the deme-formation hypothesis, they do demonstrate significant variation in the resistance traits of a natural tree population. Although we feel that demeformation is still probable in this system, it is likely to occur on a larger geographic scale than individual trees as proposed by Edmunds and Alstad.

Key words

Deme formation Fine-scale adaptation Host plant resistance Matsucoccus acalyptus Pinus edulis 


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Copyright information

© Springer-Verlag 1993

Authors and Affiliations

  • Neil S. Cobb
    • 1
  • Thomas G. Whitham
    • 1
  1. 1.Department of Biological SciencesNorthern Arizona UniversityFlagstaffUSA

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