Evolutionary Ecology

, Volume 9, Issue 4, pp 382–396

Variation in the intensity of pollination inDrosera tracyi: Selection is strongest when resources are intermediate

  • Paul Wilson

DOI: 10.1007/BF01237761

Cite this article as:
Wilson, P. Evol Ecol (1995) 9: 382. doi:10.1007/BF01237761


I propose that the strength of selection is greatest when resource levels are intermediate. This idea was partially tested using artificial character variation for petal size inDrosera tracyi. This plant opens one flower each morning, with stigmas becoming available and pollen being presented simultaneously throughout the population. Bees remove all the pollen that can be removed and deposit all the pollen that can be deposited in one or two visits. Visitation rates track blooming density, as do pollen removal and deposition. I measured selection as the difference in pollen removal and deposition between flowers with trimmed petals versus flowers with normal petals. In one meadow, I found a wide range of levels of pollination and corresponding levels of selection, and selection was strongest at intermediate levels of pollination. This might mean that organisms are adapted to conditions when resources are at intermediate levels even though they may experience those conditions relatively rarely.


Drosera tracyi natural selection pollination resource levels 

Copyright information

© Chapman & Hall 1995

Authors and Affiliations

  • Paul Wilson
    • 1
  1. 1.Harvard Forest and Department of Organismic and Evolutionary BiologyHarvard UniversityCambridgeUSA

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