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RATES OF FLORAL EVOLUTION: ADAPTATION TO BUMBLEBEE POLLINATION IN AN ALPINE WILDFLOWER, POLEMONIUM VISCOSUM
Author(s) -
Galen Candace
Publication year - 1996
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/j.1558-5646.1996.tb04478.x
Subject(s) - bumblebee , biology , pollinator , pollination , wildflower , ecology , adaptation (eye) , selection (genetic algorithm) , zoology , pollen , neuroscience , artificial intelligence , computer science
Animal pollinators are thought to shape floral evolution, yet the tempo of this process has seldom been measured. I used the prediction equation of quantitative genetics, R = h 2 S , to predict the rate at which a change in pollinator abundance may have caused divergence in floral morphology of the alpine skypilot, Polemonium viscosum . A selection experiment determined the rate at which such divergence can actually proceed. Corolla flare in this species increases by 12% from populations pollinated by a wide assemblage of insect visitors to those pollinated only by bumblebees. To simulate the evolutionary process giving rise to this change, I used a pollinator selection experiment. Plants with broad flowers set significantly more seeds than plants with narrow flowers under bumblebee pollination but had equivalent fecundity when visited by other insects or hand‐pollinated. Bumblebee‐mediated selection for broad corolla flare intensified from 0.07 at seed set to 0.17 at progeny establishment. Maternal parent‐offspring regression yielded a confidence interval of 0.22–1.00 for trait heritability. Given these parameter estimates, the prediction equation shows that broadly flared flowers of bumblebee‐pollinated P. viscosum could have evolved from narrower ones in a single generation. This prediction is matched by an observed 9% increase in offspring corolla flare after a single bout of bumblebee‐mediated selection, relative to offspring of unselected controls. Findings show that plant populations can adapt rapidly to abrupt changes in pollinator assemblages.