Research Macroevolutionary patterns of glucosinolate defense and tests of defense-escalation and resource availability hypotheses N. Ivalu Cacho1,2, Daniel J. Kliebenstein3,4 and Sharon Y. Strauss1 1Center for Population Biology, and Department of Evolution of Ecology, University of California, One Shields Avenue, Davis, CA 95616, USA; 2Instituto de Biologıa, Universidad Nacional Autonoma de Mexico, Circuito Exterior, Ciudad Universitaria, 04510 Mexico City, Mexico; 3Department of Plant Sciences, University of California. One Shields Avenue, Davis, CA 95616, USA; 4DynaMo Center of Excellence, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark Summary Author for correspondence: We explored macroevolutionary patterns of plant chemical defense in Streptanthus (Brassi- N. Ivalu Cacho caceae), tested for evolutionary escalation of defense, as predicted by Ehrlich and Raven’s Tel: +1 530 304 5391 plant–herbivore coevolutionary arms-race hypothesis, and tested whether species inhabiting Email:
[email protected] low-resource or harsh environments invest more in defense, as predicted by the resource Received: 13 April 2015 availability hypothesis (RAH). Accepted: 8 June 2015 We conducted phylogenetically explicit analyses using glucosinolate profiles, soil nutrient analyses, and microhabitat bareness estimates across 30 species of Streptanthus inhabiting New Phytologist (2015) 208: 915–927 varied environments and soils. doi: 10.1111/nph.13561 We found weak to moderate phylogenetic signal in glucosinolate classes