PMS on color and size

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Floral evolution of irises pollinator-mediated
selection for color and size
Yuval Sapir Dept. of Evolution, Systematics and
Ecology The Hebrew University of Jerusalem
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Pollinators-mediated selection (PMS) (Grant,
1949 Stebbins, 1974)

• Pollinators create selection on floral traits by
  their preferences
• Floral traits are adaptation for pollination
• Correlated floral traits Pollination syndromes
• Pollination systems as isolating mechanisms

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PMS on flower size
(e.g., Nilsson 1988 Galen 1989 Campbell et al.
1991 Johnston 1991 Schemske and Agren 1995
Campbell et al. 1996 Conner and Rush 1996
Gilbert et al. 1996 Campbell et al. 1997
Totland et al. 1998 Caruso 2000 Gomez 2000
Caruso 2001 Alexandersson and Johnson 2002 Elle
and Carney 2003 Medel et al. 2003)
Fitness
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PMS on flower color
(Stanton et al. 1986 Stanton et al. 1989
Steiner et al. 1992 Fry and Rausher 1997 Gomez
2000 Landeck 2002)
Fitness
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Oncocyclus irises

• Characteristics
• Large single flower
• Dark-colored petals
• Self-incompatible
• No nectar
• Pollination by night-sheltering male bees

Iris atrofusca
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Pollination by night-sheltering male bees

• Male Eucerinii bees enter before sunset
• Sheltering during night, flying after sunrise
• MALES ONLY
• Pollination occur during seeking behavior

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The main questions

1. Why are the flowers dark?
2. Why are the flowers so large?

• Or
• Do the night-sheltering male bees prefer dark and
  large flowers?
• What is the reward for the night-sheltering male
  bees?

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Preferences for night-shelter effects of color
and size