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ARS Home » Plains Area » Fort Collins, Colorado » Center for Agricultural Resources Research » Rangeland Resources & Systems Research » Research » Publications at this Location » Publication #296354
Title: Chemical and mechanical defenses vary among maternal lines and leaf ages in Verbascum thapsus L. (Scrophulariaceae) and reduce palatability to a generalist insect

Author
item ALBA, CHRISTINA - Academy Of Sciences Of The Czech Republic (ASCR)
item BOWERS, DEANE - Colorado State University
item Blumenthal, Dana
item HUFBAUER, RUTH - Colorado State University

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2014
Publication Date: 8/15/2014
Citation: Alba, C., Bowers, D., Blumenthal, D.M., Hufbauer, R. 2014. Chemical and mechanical defenses vary among maternal lines and leaf ages in Verbascum thapsus L. (Scrophulariaceae) and reduce palatability to a generalist insect. PLoS One. 9:3104889.

Interpretive Summary: Among- and within-plant variation in defense shapes herbivore behavior, and if genetically based, may respond to natural selection by herbivores. We quantified variation in both mechanical and chemical defense in common mullein (Verbascum thapsus L, Scrophulariaceae), and related this variation to feeding preferences of a generalist caterpillar, Trichopulsia ni. We found significant variation in both types of defenses among maternal lines, with T. ni preferring plants with lower investment in chemical, but not mechanical, defense. Within plants, old leaves had lower levels of all defenses than young leaves, and were strongly preferred by T. ni. These results indicate a likely genetic basis for variation in defense, and reveal that the feeding behaviors of T. ni map onto plant variation in defense in a predictable way. This shows the importance of variation in host-plant quality in driving interactions between plants and their herbivores.

Technical Abstract: Intra-specific variation in host-plant quality affects herbivore foraging decisions and, because of this, can feed back to shape plant fitness. In particular, among- and within plant variation in defense shapes herbivore behavior, and if genetically based, may respond to natural selection by herbivores. We quantified intra-specific variation in iridoid glycosides, trichome length, and leaf strength in common mullein (Verbascum thapsus L, Scrophulariaceae) among maternal lines within a population and leaves within plants, and related this variation to feeding preferences of a generalist herbivore, Trichopulsia ni Hübner. We found significant variation in all three defenses among maternal lines, with T. ni preferring plants with lower investment in chemical, but not mechanical, defense. Within plants, old leaves had lower levels of all defenses than young leaves, and were strongly preferred by T. ni. Caterpillars also preferred leaves with trichomes removed to leaves with trichomes intact. These results indicate a likely genetic basis for phenotypic variation in defense, and reveal that the feeding behaviors of T. ni map onto plant variation in defense in a predictable way. This shows the importance of variation in host-plant quality in driving interactions between plants and their herbivores.