Selection for chemical trait remixing in an invasive weed after reassociation with a coevolved specialist
- *Department of Entomology, 320 Morrill Hall, University of Illinois at Urbana-Champaign, 505 South Goodwin, Urbana, IL 61801-3795; and
- †School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland Mail Centre, Auckland 1142, New Zealand
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Edited by Jerrold Meinwald, Cornell University, Ithaca, NY, and approved December 19, 2007 (received for review November 1, 2007)
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Fig. 1.Realized fitness of wild parsnips in six N.Z. populations after consumption of reproductive parts by parsnip webworms. Average potential fitness (number of male flowers) of plants within a population is given below each pie chart. Estimates of potential fitness for many plants was not possible because webworms in addition to consuming all of the umbels had as well consumed the stalks bearing the umbels.
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Fig. 2.Clustering of 33 wild parsnip populations (involving 1,117 individuals) on the basis of average phenotypic furanocoumarin seed content; North American and European data are from Berenbaum and Zangerl (21). Populations in red have had either long-term associations with webworms [in the cases of North American, prefixed “na,” or European populations (green) from Austria, The Netherlands, or Germany, prefixed “aust,” “neth,” or “germ”] or only a recent association (between 2004 and 2006 in New Zealand, “nz”). Populations in black have had no, or only rare, interaction with webworms. Clustering is based on squared Euclidean distances (SPSS 14, Chicago, IL). Bar graphs show percent deviations (+ or −) from mean furanocoumarin content of each of six clusters for five furanocoumarins (left to right: imperatorin, bergapten, isopimpinellin, xanthotoxin, and sphondin). With one exception (nzLUMB), N.Z. populations are clustered separately from all others. Abbreviated N.Z. population names are LUMB, Lumber; TOWN, Townley; WAR, Warrington; COTT, Cottage; and OCEA, Ocean.
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Fig. 3.Differences between N.Z. and Midwest U.S. parsnips in chemical composition of buds and male flowers (means ± SE). All differences but those for cis- and trans-ocimene between countries were significant (P < 0.05) in a two-way ANOVA with country and plant part (bud or flower) as main effects. There were no significant interactions and only three compounds differed between buds and flowers: flowers were higher in octyl butyrate and lower in myristicin and cis-ocimene (data not shown).
Footnotes
- ‡To whom correspondence should be addressed. E-mail: maybe{at}uiuc.edu
- © 2008 by The National Academy of Sciences of the USA
