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CONSTRAINTS ON THE EVOLUTION OF TOLERANCE TO HERBICIDE IN THE COMMON MORNING GLORY: RESISTANCE AND TOLERANCE ARE MUTUALLY EXCLUSIVE
Author(s) -
Baucom Regina S.,
Mauricio Rodney
Publication year - 2008
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.1558-5646.2008.00514.x
Subject(s) - biology , trade off , resistance (ecology) , glyphosate , selection (genetic algorithm) , context (archaeology) , population , pest analysis , microbiology and biotechnology , agronomy , botany , ecology , paleontology , demography , artificial intelligence , sociology , computer science
Evolutionary biologists explain the maintenance of intermediate levels of defense in plant populations as being due to trade‐offs, or negative genetic covariances among ecologically important traits. Attempts at detecting trade‐offs as constraints on the evolution of defense have not always been successful, leading some to conclude that such trade‐offs rarely explain current levels of defense in the population. Using the agricultural pest Ipomoea purpurea , we measured correlations between traits involved in defense to glyphosate, the active ingredient in Roundup, a widely used herbicide. We found significant allocation costs of tolerance, as well as trade‐offs between resistance and two measures of tolerance to glyphosate. Selection on resistance and tolerance exhibited differing patterns: tolerance to leaf damage was under negative directional selection, whereas resistance was under positive directional selection. The joint pattern of selection on resistance and tolerance to leaf damage indicated the presence of alternate peaks in the fitness landscape such that a combination of either high tolerance and low resistance, or high resistance and low tolerance was favored. The widespread use of this herbicide suggests that it is likely an important selective agent on weed populations. Understanding the evolutionary dynamics of herbicide defense traits is thus of increasing importance in the context of human‐mediated evolution.