Escalada química macroevolutiva numa antiga corrida armamentista entre plantas e herbíveros

Macroevolutionary chemical escalation in an ancient plant–herbivore arms race

Judith X. Becerraa,1, Koji Nogeb and D. Lawrence Venablec

+ Author Affiliations

Departments of aBiosphere 2 and

cEcology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721; and

bDepartment of Biological Production, Akita Prefectural University, Akita 010-0195, Japan

Abstract

A central paradigm in the field of plant–herbivore interactions is that the diversity and complexity of secondary compounds in plants have intensified over evolutionary time, resulting in the great variety of secondary products that currently exists. Unfortunately, testing of this proposal has been very limited. We analyzed the volatile chemistry of 70 species of the tropical plant genus Bursera and used a molecular phylogeny to test whether the species' chemical diversity or complexity have escalated. The results confirm that as new species diverged over time they tended to be armed not only with more compounds/species, but also with compounds that could potentially be more difficult for herbivores to adapt to because they belong to an increasing variety of chemical pathways. Overall chemical diversity in the genus also increased, but not as fast as species diversity, possibly because of allopatric species gaining improved defense with compounds that are new locally, but already in existence elsewhere.

Bursera chemical complexity chemical diversity evolution of secondary compounds coevolution

Footnotes

1To whom correspondence should be addressed. E-mail: jxb@email.arizona.edu

Author contributions: J.X.B. designed research; J.X.B. and D.L.V. performed research; K.N. contributed new reagents/analytic tools; J.X.B., K.N., and D.L.V. analyzed data; and J.X.B. and D.L.V. wrote the paper.

Edited by Anurag A. Agrawal, Cornell University, Ithaca, NY, and accepted by the Editorial Board July 8, 2009

The authors declare no conflict of interest.

This article is a PNAS Direct Submission. A.A.A. is a guest editor invited by the Editorial Board.

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