Evolutionary change from induced to constitutive expression of an indirect plant resistance

• Published in: Nature Vol. 430; no. 6996; pp. 205 - 208
• Main Authors: Heil, M, Greiner, S, Meimberg, H, Kruger, R, Noyer, J.L, Heubl, G, Linsenmair, K.E, Boland, W
• Format: Journal Article
• Language: English
• Published: London Nature Publishing 08.07.2004; Nature Publishing Group
• Subjects: Acacia; Acacia - classification; Acacia - drug effects; Acacia - genetics; Acacia - metabolism; amplified fragment length polymorphism; Animal and plant ecology; Animal, plant and microbial ecology; Animals; Ants - physiology; Biological and medical sciences; Biological Evolution; chloroplast DNA; Cyclopentanes - metabolism; defoliation; Evolution; extrafloral nectar secretion; Fabaceae; Flowers & plants; Formicidae; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Plant; genes; Herbivores; insect pests; Insects; jasmonic acid; leaf damage; Leaves; Mimosoideae; Molecular Sequence Data; mutualism; myrmecophytes; nectar secretion; nectaries; Oxylipins; pest resistance; Phenotype; Phylogeny; phytophagous insects; Plant Diseases; Plant Leaves - drug effects; Plant Leaves - metabolism; Plant Leaves - physiology; Plant resistance; Plant species; Pyrazoles - pharmacology; Symbiosis; Synecology; Terrestrial ecosystems; Mexico; Central America; Symbiosis; Nectar; Formicidae; Secretion; Insecta; Biological evolution; Woody plant; Phylogeny; Induced resistance; Formicoidea; Phytophagous; Leguminosae; Animal plant relation; Arthropoda; Dicotyledones; Myrmecophilous; Angiospermae; Acacia; Spermatophyta; Hymenoptera; Invertebrata; Aculeata
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature02703

Induced plant resistance traits are expressed in response to attack and occur throughout the plant kingdom. Despite their general occurrence, the evolution of such resistances has rarely been investigated. Here we report that extrafloral nectar, a usually inducible trait, is constitutively secreted by Central American Acacia species that are obligately inhabited by ants. Extrafloral nectar is secreted as an indirect resistance, attracting ants that defend plants against herbivores. Leaf damage induces extrafloral nectar secretion in several plant species; among these are various Acacia species and other Fabaceae investigated here. In contrast, Acacia species obligately inhabited by symbiotic ants nourish these ants by secreting extrafloral nectar constitutively at high rates that are not affected by leaf damage. The phylogeny of the genus Acacia and closely related genera indicate that the inducibility of extrafloral nectar is the plesiomorphic or 'original' state, whereas the constitutive extrafloral nectar flow is derived within Acacia. A constitutive resistance trait has evolved from an inducible one, obviously in response to particular functional demands.