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Petal Power in Monkeyflowers

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Bees and birds have clear preferences when it comes to the plants they visit for nectar, and one little tweak in the plant's genetic material can radically change their interests.

Monkeyflowers clad themselves in bright colors to lure pollinators deep into their blossoms. Just one small part of the genome of Mimulus wildflowers, possibly one gene--Yellow Upper or YUP--appears to determine where bees and birds go to find their supper. The gene is thought to code for yellow carotenoid pigment in petals.

The red color of Mimulus cardinalis attracts hummingbirds but goes unnoticed by bumblebees. Bumblebees prefer the pale pink petals of Mimulus lewisii, which in turn are unpopular with birds.

The monkeyflower Mimulus lewisii is usually pink and pollinated by bees (left). One mutated gene, which is responsible for the yellow-orange petals (right), causes the bees to drop their visits and hummingbirds to pollinate the plant.

Mimulus cardinalis is usually red and pollinated by hummingbirds (left). The altered version (right) is dark pink and attracts 74 times more bee visits than the type that occurs in nature.

In a field test in California, researchers swapped the YUP gene of two Mimulus species and cataloged the pollinators' responses. The altered Mimulus cardinalis with dark pink flowers got 74 times more bee visits than the wild type, whereas Mimulus lewisii with yellow-orange petals received 68 times more visits from hummingbirds.

The findings show that evolutionary adaptations may not always depend on complex changes. Even a single mutation can have a big effect.

More information on monkeyflowers is available through the Mimulus Biological Resource Center here.

Birgit Reinert

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Bradshaw Jr., H.D. & Schemske, D.W. Allele substitution at a flower colour locus produces a pollinator shift in monkeyflowers. Nature 426, 176-178 (November 13, 2003).


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