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CONSEQUENCES OF GLOBAL REDISTRIBUTION ON THE ECOLOGY AND EVOLUTION OF THE INVASIVE WEED PASTINACA SATIVA AND ITS ASSOCIATED INSECT FAUNA BY TANIA JOGESH DISSERTATION Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Entomology in the Graduate College of the University of Illinois at Urbana‐Champaign, 2014 Urbana, Illinois Doctoral Committee: Professor May R. Berenbaum, Chair, Director of Research Professor Stephen R. Downie Professor Stewart H. Berlocher Professor Lawrence M. Hanks Assistant Professor Alexandra N. Harmon‐Threatt 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 ii 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. iii Acknowledgments First and foremost I would like to thank my advisor May Berenbaum for her support, encouragement and invaluable input throughout my graduate career – she has been nothing short of amazing. None of this work would have been possible without Art Zangerl, whose prior work, impeccable experimental design, and mentorship set the stage for my experiments. I am also extremely grateful to Margaret Stanley, who, in spite of being in another hemisphere, helped extensively with many aspects of this research. Thanks to Stephen Downie for providing me lab‐space, resources and advice on my molecular work. Thanks also to Rhiannon Perry, who taught me so much about molecular analysis and lab techniques, not to mention helping me troubleshoot so many difficult PCRs. Thanks to Paul Ode for collecting parsnip samples out west. I would also like to thank my thesis committee Larry Hanks, Stewart Berlocher and Alexandra Harmon‐Threatt for their input and advice. Thanks to Terry Harrison for advice on all things Lepidoptera and for sexing my moths countless time. I am grateful to all of the high‐ school and undergraduate students who helped me in the field and in the lab, in spite of the photodermatitis and the 100oF summer weather in Urbana or the cold rainy days in Dunedin. I am especially thankful to Alex Shaw and the NZ crew who took on the mind‐numbing task of cleaning and sorting parsnip seeds. All members of the Berenbaum lab have been absolutely fantastic and I am grateful for the opportunity to work with such amazing people. They have been my surrogate family here while my mother, father, and sister gave me their loving support overseas. Finally, thanks to my husband, Johnny Yu, for helping me with lab work and field work on weekends, driving me throughout Europe to scout for parsnips, for his patience and for all the coffee, chocolates and love. iv Dedication For Art Zangerl Who was an incredible mentor and to whom I owe so much of this dissertation. His warmth and laughter are dearly missed v Table of Contents Introduction .................................................................................................................................... 1 Chapter 1 ‐ Implications of enemy escape on chemically mediated interactions with mutualists: wild parsnip pollination in two hemispheres ............................................................................... 17 Chapter 2 ‐ Real‐time evolution of tolerance in an invasive weed after reassociation with its specialist herbivore ....................................................................................................................... 48 Chapter 3 ‐ Impact of reassociation with a coevolved herbivore on oviposition deterrence in a hostplant: Depressaria pastinacella and Pastinaca sativa ........................................................... 92 Chapter 4 ‐ Population genetic structure and colonization history of the globally‐invasive weed wild parsnip (Pastinaca sativa) ................................................................................................... 122 Conclusions ................................................................................................................................. 163 Appendix: DNA sequences .......................................................................................................... 166 vi Introduction Globalization in trade has resulted in a dramatic increase in the number of exotic species worldwide (Mack et al. 2000; Palumbi 2001). Exotic invasions can be extremely detrimental to native ecosystems (e.g. Mooney and Cleland 2001; Pimentel et al. 2005), but they also provide a large‐scale experiment in evolutionary biology (Sax et al. 2007). The altered genetic structure of founding populations along with novel selection pressures pave the way for rapid evolution in invasive populations. Recently documented invasions offer a unique opportunity to study the fundamental ecological and evolutionary processes of colonization and adaptation. A remarkable diversity of plant traits have been attributed to insect‐mediated evolution. Many plants require insects for pollination and also contend with detrimental insect herbivory. Both mutualistic pollinators and antagonistic herbivores can have a strong impact on plant fitness and can thus impose selection on defense, morphological, and life‐history traits. The role of herbivores and pollinators in the evolution of plants has been inferred via correlations between phenotypes and fitness and recently through long‐term herbivore exclusion experiments (Agrawal et al. 2012; Turley et al 2013). Exotic invasions provide an opportunity to observe herbivore‐ and pollinator‐mediated evolution as it occurs. When a plant is introduced to a new range, it generally leaves behind its coevolved specialist herbivores (Keane and Crawley 2002). Escape from natural enemies might result in relaxed defenses and increased pollinator attraction, especially if herbivores and pollinators impose conflicting selection pressures. On rare occasions, coevolved specialist herbivores are co‐introduced, either 1 deliberately as biological control agents or accidentally. These plant‐herbivore reassociations provide an opportunity to observe how plants respond to selection by herbivores and how herbivore‐mediated selection alters interactions with pollinators. For evolution to occur in an invasive species, adequate genetic variation must exist for selection to act upon. It has been widely assumed that invasive populations suffer genetic bottlenecks upon introduction because of small founding populations (Bossdorf et al. 2005). However,