Foliage color contrasts and adaptive fruit color variation in a bird-dispersed plant community


  • K. C. Burns,

  • J. L. Dalen

K. C. Burns, Dept of Organismic Biology, Ecology, and Evolution, Univ. of California LA, 621 Charles Young Drive, Box 951606, Los Angeles, CA 90095-1606, USA ( Present address: School of Biological Sciences, Victoria Univ. of Wellington, P.O. Box 600, Wellington, New Zealand. – J. L. Dalen, Dept of Biology, Univ. of New Brunswick, Fredericton, NB, Canada E3B 6E1. Both authors also at: Bamfield Marine Station, Bamfield, BC, Canada V0R 1B0.


The color of vertebrate-dispersed fruits has been a source of inquiry for over 150 years, yet the ecological and evolutionary processes responsible for fruit color diversity remain elusive. We tested the hypothesis that fruit color varies temporally, to maximize conspicuousness against seasonal changes in foliage coloration, in a bird-dispersed plant community in western North America. Field observations showed that while red fruits predominate during summer periods of green foliage coloration, black fruits are produced during flushes of red-orange foliage coloration in autumn. Although two species did not conform to this pattern, one produced its own contrasting background color, via colored bracts. We conducted experimental manipulations of both fruit color and the color of artificial backgrounds to test whether both factors had a synergistic effect on fruit removal rates. Interactions between fruit and background color explained most of the variation in experimental fruit removal rates. Although red fruits were removed rapidly on green backgrounds, preference for black fruits on red-orange backgrounds was less pronounced. Consequently, the temporal pattern in fruit color appears to result from elevated fruit conspicuousness against seasonal changes in foliage coloration. Support for this hypothesis suggests a temporal connection between fruit color diversity, foliage color contrasts and avian color preferences.