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Title:Consequences of global redistribution on the ecology and evolution of the invasive weed Pastinaca sativa and its associated insect fauna
Author(s):Jogesh, Tania
Director of Research:Berenbaum, May R.
Doctoral Committee Chair(s):Berenbaum, May R.
Doctoral Committee Member(s):Downie, Stephen R.; Hanks, Lawrence M.; Berlocher, Stewart H.; Harmon-Threatt, Alexandra N.
Department / Program:Entomology
Degree Granting Institution:University of Illinois at Urbana-Champaign
Invasive Species
Plant-insect interactions
Abstract:Biological invasions can provide useful insights on how communities persist and change over space and time. The wild parsnip (Pastinaca sativa L., Apiaceae) and its coevolved specialist florivore, the parsnip webworm (Depressaria pastinacella Duponchel, Lepidoptera: Oecophoridae), are native to Europe but they occur as an invasive association throughout the temperate world. New Zealand (NZ) populations of wild parsnips were free from webworm herbivory for 140 years until 2004, when webworms were discovered, presumably having been accidentally introduced. This escape and subsequent reassociation of wild parsnips with parsnip webworms in NZ presented a unique opportunity to study herbivore-mediated evolution as it occurs. In Chapter 1, I examined the chemical mediation of wild parsnip pollination to understand selection pressures imposed by both florivores and pollinators. In Chapter 2, I evaluated phenotypic evolution in wild parsnips after six years of webworm infestation (2004 – 2009) in a large-scale common garden experiment. In Chapter 3, I identified leaf volatiles that mediate oviposition by webworms to determine whether plants can experience selection to deter oviposition. In Chapter 4, I used ribosomal internally transcribed spacers (ITS) and chloroplast markers to determine the colonization history of wild and cultivated parsnips in three geographic regions: Eastern North America, Western North America and New Zealand. Results from these studies showed that volatile chemical signals mediate pollination by flies and webworm oviposition in wild parsnips. Floral volatile compounds positively associated with pollinator visitation were produced in higher proportions in NZ flowers, suggesting that in the absence of specialized florivores, NZ flowers may be chemically better constituted to attract pollinators. In the common garden, defensive chemistry remained unchanged in both infested and uninfested New Zealand populations; however, plants in infested populations were larger after three to six years of webworm florivory. Evolution of large size as a component of florivore tolerance may occur more rapidly than evolution of enhanced chemical defense. While adult moths were deterred by leaf volatiles, oviposition counts did not correspond with lower fitness and, consistent with this finding, infested NZ parsnips showed no phenotypic change in leaf volatiles after reassociation with parsnip webworms. However, leaf volatiles implicated as oviposition deterrents were positively correlated with floral defenses, suggesting that webworm adults choose hosts based on larval suitability. Finally, the analysis of molecular markers in wild parsnips showed high genetic diversity in all three geographic regions of invasion. The haplotype distribution from chloroplast markers suggests that parsnips in North America originated from wild and cultivated haplotypes, whereas NZ parsnips are primarily escapees from cultivation. These findings illustrate the complexity of chemically mediated biotic interactions that are lost and regained by multiple invasions, the potential for rapid adaptive evolution in response to shifting biotic selection pressures, and the availability of genetic variation from agricultural or accidental introductions that can provide the raw material for evolution.
Issue Date:2014-05-30
Rights Information:Copyright 2014 Tania Jogesh
Date Available in IDEALS:2014-05-30
Date Deposited:2014-05

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