Coevolution can explain defensive secondary metabolite diversity in plants

Many plant species produce defensive compounds that are often highly diverse within and between populations. The genetic and cellular mechanisms by which metabolite diversity is produced are increasingly understood, but the evolutionary explanations for persistent diversification in plant secondary...

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Bibliographic Details
Published in:The New phytologist 2015-12, Vol.208 (4), p.1251-1263
Main Authors: Speed, Michael P, Fenton, Andy, Jones, Meriel G, Ruxton, Graeme D, Brockhurst, Michael A
Format: Article
Language:English
Subjects:
Animals
Biological Evolution
chemical defence
Coevolution
Evolution
Fitness
Genetic Fitness
herbivore
Herbivores
Herbivory
Insecta - genetics
Insects
Metabolites
Model testing
Pest resistance
Phenotype
phytotoxins
Plant Diseases
Plant diversity
Plant species
Plants - genetics
Plants - metabolism
Population genetics
Populations
Reproductive fitness
Secondary Metabolism
secondary metabolite
Secondary metabolites
specialized metabolism
theoretical modelling
Toxins
Toxins, Biological - metabolism
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Summary:Many plant species produce defensive compounds that are often highly diverse within and between populations. The genetic and cellular mechanisms by which metabolite diversity is produced are increasingly understood, but the evolutionary explanations for persistent diversification in plant secondary metabolites have received less attention. Here we consider the role of plant–herbivore coevolution in the maintenance and characteristics of diversity in plant secondary metabolites. We present a simple model in which plants can evolve to invest in a range of defensive toxins, and herbivores can evolve resistance to these toxins. We allow either single‐species evolution or reciprocal coevolution. Our model shows that coevolution maintains toxin diversity within populations. Furthermore, there is a fundamental coevolutionary asymmetry between plants and their herbivores, because herbivores must resist all plant toxins, whereas plants need to challenge and nullify only one resistance trait. As a consequence, average plant fitness increases and insect fitness decreases as number of toxins increases. When costs apply, the model showed both arms race escalation and strong coevolutionary fluctuation in toxin concentrations across time. We discuss the results in the context of other evolutionary explanations for secondary metabolite diversification.
ISSN:0028-646X
1469-8137
DOI:10.1111/nph.13560