Plant-Insect Interactions Population Ecology Behavioral Ecology Chemical Ecology Community Ecology Ecosystem Ecology
My research interests focus on the ecology and evolution of interactions between plants and herbivores. My goal is to understand why insects eat what they do and to approach this research by asking questions at multiple scales, from populations to communities to ecosystems. At the scale of populations, I am interested in why some herbivorous insects are specialists while others are generalists and how each of these groups choose their host plants. At the scale of communities, I seek to understand how natural enemies affect community structure and population dynamics of herbivorous insects. Finally, at the ecosystem scale, I study how nutrient cycling and resource subsidies may affect interactions between herbivorous insects and their host plants both directly as well as indirectly by altering the impact that natural enemies and detritivores have on populations of herbivores.
Graduate Research on Insect Host Shifts
Chemical facilitation of a host shift
Host shifts by herbivorous insects have contributed substantially to current patterns of association between insects and plants by influencing the diversification and speciation of plant-feedinginsects. Furthermore, many of our major agricultural pests have colonized crop plants by shifting from native food-plants to an abundant crop host. Despite their evolutionary and agricultural interest, however, the plant traits that predispose insects to colonize some plants instead of others are poorly understood. My research on a fairly recent host shift within a closely related group of swallowtail butterflies known as the Papilio machaon group, experimentally tests the mechanisms by which host shifts are thought to occur. In collaboration with my graduate advisor, Paul Feeny, I fractionated and isolated chemical stimulants in the ancestral and novel host plants used by two P. machaon swallowtails (P. m. aliaska and P. oregonius). After a series of behavioral bioassays, we found that the novel and ancestral host plants share similar chemical stimulants that may have facilitated the host shift by swallowtails within the P. machaon group. Chemical similarities between plants have often been suggested as a possible explanation for insect host shifts but our research is the first experimental test to document the role of plant chemistry during an insect host-shift. Our research supports the chemical facilitation hypothesis of host race formation.
The role of enemy-free space during a host shift
Natural enemies can be significant sources of mortality for herbivorous insects and thereforeimportant agents of natural selection. One might expect selection to favor herbivores that escape from their natural enemies into enemy-free space (EFS). While this is an appealing idea, it has received little empirical support and no studies have documented EFS as part of a non-agricultural, naturally-occurring host shift. I designed a field experiment to test whether the novel host plants offer P. m. aliaska larvae EFS that is not found on the ancestral host plant. I found that P. m. aliaska larvae find refuge from their natural enemies (mostly ants, see photo to the right) by feeding on novel host plants; this appears to be an example of EFS via host-plant dispersion rather than via host-plant chemistry. This study is the first to experimentally demonstrate that EFS can play an important role in maintaining a host expansion or shift in a natural system.
Do host races exist in the Alaskan swallowtail system?
Specialized insect species that feed on unrelated host plants may be composed of separate host races, with populations that specialize on the different host plants. The Alaskan swallowtail butterfly (P. m. aliaska) uses three unrelated plant species as hosts. I investigated variation in adult oviposition preferences for the three host species to identify whether host races may exist in this swallowtail species. The results from all of these experiments indicate that P. m. aliaska females vary greatly in their oviposition behavior and in their preferences for the three host plants. Most populations appear to be comprised of generalists; there is no evidence to support the hypothesis that P. m. aliaska populations in central Alaska are divided into host races. The results of this research suggest an explanation for why P. m. aliaska continues to use all three host-plants in nature. I propose that the generalized selection of host plants by P. m. aliaska females is a ‘bet-hedging’ strategy and this strategy may maximize reproductive fitness in an unpredictable environment.
Postdoctoral Research on Nutrient Subsidies and Foodweb Dynamics
For the past three years, I have conducted research as a National Parks Ecological Research (NPER) Postdoctoral Fellow and have been working with Bob Denno in the Department of Entomology at the University of Maryland. I am investigating how nutrient subsidies affect foodweb dynamics within salt marsh communities. Natural wetlands are increasingly threatened by nutrient pollution and invasive plant species. I am studying the contrasting effects of a short-term increase in nutrient availability (pulse) versus a long-term increase in nutrients (press) on the productivity of the cordgrass Spartina alterniflora, with extended consequences for species interactions, food-web structure and food chain length. As a dominant species, Spartina is an important component of the vegetation of Atlantic coastal marshes. Conservation of coastal wetlands, particularly salt marshes, is a major concern because these play a critical role in the ecology and geology of wave-protected shorelines and are the nursery grounds for commercial fish and shellfish. The treatments that I have imposed are specifically designed to mimic nutrient-runoff from agricultural fields and golf courses in order to understand, for conservation and management purposes, how variable nutrient regimes influence community structure over time. Remarkably, the effects of contrasting nutrient-input regimes on food-web structure in native habitats remain poorly understood in terrestrial systems, despite the increasing fraction of landscapes affected by nutrient runoff from agriculture and development.
Postdoctoral Research on the Evolution of Polyphagy
I am currently a Postdoctoral Scientist in the laboratory of Dr. John Lill at the George Washington University with funding from NSF. We are investigating the evolution of diet breadth for generalist species, specifically focusing on polyphagous slug caterpillars (Lepidoptera: Limacodidae). Specialist insects have been widely studied, while comparatively little is known about the evolutionary ecology of generalists. This is one of the first studies to investigate how polyphagy is maintained in generalist insect species. A tri-trophic view that encompasses both host plant characteristics and predation is often evoked when explaining why specialist insects are specialists. Here we attempt to understand how tri-trophic interactions may also function to maintain polyphagous habits for generalist species.
Slug caterpillars (Limacodidae) are known for their unusual morphologies, including various types of protuberances and stinging spines on their dorsal surfaces, which suggest that their evolution has been strongly shaped by their interactions with predators. One of the projects that we have been working on with two undergraduate students in the lab, Susannah Leahy and Laila Williams, investigates whether the stinging spines of one slug caterpillar in particular, Acharia stimulea, are an effective defense against arthropod predators. In a series of bioassays, we tested the preferences of assassin bugs and paper wasps for spined (Acharia stimulea) or unspined larvae (unspined limacodids or army worms). Our results demonstrate that these sptinging spines don't only deter us (they hurt!), but also the invertebrate predators that we tested. Our manuscript is currently in press at Behavioral Ecology, but you can see some of the interactions between the wasps and the stinging Acharia stimulea caterpillars below!
This first video shows a paper wasp that is trying to kill the Acharia caterpillar. You can see that the caterpillar "flexes" its spines towards her to ward her off. Just double click on the picture to get the video to play.
This second video shows a paper wasp that has successfully killed the Acharia caterpillar; only 4 wasps ever managed to do so. Notice how she cuts the spines off before she returns with it to her nest. Just double click on the picture to get the video to play.
(*denotes undergraduate co-author)
Kula, R. R., J. T. Lill, S. M. Murphy and T. Stoepler. In Press. The first host records for the nearctic species Triraphis discoideus (Hymenoptera: Braconidae: Rogadinae). Entomological News.
Murphy, S. M., S. Leahy*, L. Williams* and J. T. Lill. 2010. Stinging spines protect slug caterpillars (Limacodidae) from multiple generalist predators. Behavioral Ecology 21(1): 153-160.pdf
Murphy, S. M., J. T. Lill and D. R. Smith. 2009. A scattershot approach to host location: Uncovering the unique life history of the Trigonalyid hyperparasitoid Orthogonalys pulchella Cresson. American Entomologist 55(2): 82-87. pdf
Murphy, S. M. 2008. Notes on Papilio machaon aliaska (Papilionidae) populations near Fairbanks, AK. Journal of the Lepidopterists' Society 62(2): 80-83. pdf
Murphy, S. M. 2007. Inconsistent use of host plants by the Alaskan swallowtail butterfly: Adult preference experiments suggest labile oviposition strategy. Ecological
Entomology 32: 143-152. pdf
Murphy, S. M. 2007. The effect of host plant on larval survivorship of the Alaskan swallowtail butterfly (Papilio machaon aliaska). Entomologia Experimentalis et Applicata 122: 109-115. pdf
Murphy, S. M. and P. P. Feeny. 2006. Chemical facilitation of a naturally-occurring host shift by Papilio machaon butterflies (Papilionidae). Ecological Monographs
76(3): 399-414. pdf
Murphy, S. M. 2004. Enemy-free space maintains swallowtail butterfly host shift. Proceedings of the National Academy of Sciences 101(52): 18048-18052. pdf
This publication was awarded the LaMont C. Cole Award in 2005. "This award is given each year to the author of the most outstanding published paper written by a
graduate student or recent graduate of the Department of Ecology and Evolution for research carried out while at Cornell University. Papers are judged on the basis of their expected impact, originality,
scholarship and clarity."
Murphy, S. M. and Y. B. Linhart. 1999. Comparative morphology of the gastrointestinal tract in the feeding specialist Sciurus aberti and several generalist congeners. Journal of Mammalogy 80(4):1325-1330. pdf
Published Data Reports
Walker, D. A., N. A. Auerbach, T. K. Nettleton, A. Gallant, and S. M. Murphy. 1997. Arctic
System Science Flux Study Data Report. Happy Valley Permanent Vegetation Plots: site factors, physical and chemical soil properties, plant species cover, photographs, soil descriptions and ordination. Tundra Ecosystems Analysis and Mapping Laboratory, University of Colorado
Wimp, G. M., S. M. Murphy, D. L. Finke, A. F. Huberty and R. F. Denno. Increased primary production shifts the structure and composition of a terrestrial arthropod community. Submitted to Ecology.
GRANTS AND FELLOWSHIPS
2005-08 National Parks Ecological Research Fellowship ($144,000)
Ph.D. Dissertation Research
2003 American Museum of Natural History, Theodore Roosevelt Memorial
2001-03 NSF Doctoral Dissertation Improvement Grant ($12,000)
2001 Explorer’s Club Exploration Fund Grant ($1,200)
2000-03 Edna Bailey Sussman Fund Grants ($8,000)
2000-02 Sigma Xi Grants ($1,700)
2000-03 Andrew W. Mellon Student Research Grants ($2,300)
1999-04 Department of Ecology and Evolutionary Biology Grants ($2,400)
Undergraduate Honors Thesis Research
1996 Undergraduate Research Opportunities Program Grants ($600)
Field Courses and Travel Grants
2004-07 Gordon Conference Travel Grants ($1,200)
2000-04 Cornell University Conference and Travel Grants ($2,900)
2001 Organization for Tropical Studies course Tropical Biology: An Ecological
2001 National Science Foundation Graduate Research Fellowship Travel Grant ($1,000)
Fellowships (Total = $78,000)
1999-02 National Science Foundation Graduate Research Fellowship ($62,000 + tuition)
1998-99 Cornell Fellowship from the Cornell University Graduate School
($16,000 + tuition)
Total Amount of Grants Received: $259,300
2005 Excellence in Teaching Award, Department of Ecology and Evolutionary Biology,
Cornell University. This award is given each year to a single graduate student.
Courses Taught as the Instructor
2009 Honors Thesis Writing Workshop, George Washington University
2004 Writing in the Majors, Ecology and the Environment, Cornell University
1992 English Instructor, Centre Culturelle de La Madeleine, France
Courses Taught as a Teaching Assistant
2005 Herbivores and Plants: Chemical Ecology and Coevolution, Cornell University
2003 Herbivores and Plants: Chemical Ecology and Coevolution, Cornell University
2002 Evolutionary Biology, Cornell University
1998-99 Introductory Biology Laboratory Instructor, Cornell University
2002 Ithaca High School, Honors Biology classes
2004 Writing in the Majors Seminar (Education 701), Cornell University
1999 Internship in Education (Education 620), Cornell University
1999 Graduate Student Professional Development Workshop participant,
2005-07 Research advisor for University of Maryland student Christine Finke, a participant
in the College Park Scholars: Earth, Life and Time Program
2002-04 Research advisor for three Ithaca High School seniors who were participants in
the New Visions: Explorations in the Biological Sciences program, part of the Board of Cooperative Educational Services (BOCES), Ithaca, NY. I mentored Jennie Lavine (2002), Mary Kate Wheeler (2003) and Michelle Samuelsen (2004).
2001 Independent Study research co-advisor for David Bollinger, a junior at Cornell
University "Determining a definitive correlation between environmental stressors during pupal development and fluctuating asymmetries in eclosed Papilio troilus swallowtail butterfly wings"
Student Training in Field and Laboratory Techniques Cornell University: 1 High School Student (Peter Bennett) and 6 Undergraduate Students
(Christina Swanson, Crystal Tung, Joanna Goodman, Lauren Hough, Lauren Saunders and Susannah Rothman)
University of Maryland: 1 High School Student (Edgardo Parilla) and 3 Undergraduate Students
(Brian Crawford, Fiona Monosmith and Margaret Douglas)
The George Washington University: 7 Undergraduate Students (Kylee Grenis, Manaswi Sangraula, Laila Williams, Lillian Power,
Rachel Liebson, Susannah Leahy and Victoria Fiorentino)
PROFESSIONAL PRESENTATIONS (First-Authored Only)
2009 Cornell University, Department of Ecology and Evolutionary Biology
2009 University of Virginia, Blandy Experimental Farm
2009 University of Denver, Department of Biological Sciences
2009 Smithsonian Environmental Research Center
2008 Entomological Society of America, Annual Meeting: Reno, NV
2008 Smithsonian Institution, National Museum of Natural History
2008-09 Howard Hughes Medical Institute & National Science Foundation, Research Experience for Undergraduates Seminar Series at The George Washington University
2007 Georgetown University, Department of Biology
2006 University of Maryland, Department of Entomology
2005 The George Washington University, Department of Biological Sciences
2005 Cornell University, Department of Ecology and Evolutionary Biology
2004 Cornell University, Ecology and Evolutionary Biology Graduate Student Recruitment
2003 Eastern Branch of the Entomological Society of America: Harrisburg, PA
2009 Ecological Society of America, Annual Meeting: Albuquerque, NM
2008 Ecological Society of America, Annual Meeting: Milwaukee, WI
2007 Ecological Society of America, Annual Meeting: San Jose, CA
2007 Gordon Research Conference on Plant-Herbivore Interactions (poster): Ventura, CA
2006 Ecological Society of America, Annual Meeting: Memphis, TN
2005 Ecological Society of America, Annual Meeting: Montreal, Canada
2005 Society for the Study of Evolution, Annual Meeting: Fairbanks, AK
2004 Ecological Society of America, Annual Meeting: Portland, OR
2004 Society for the Study of Evolution, Annual Meeting: Fort Collins, CO
1999-06 Ecology and Evolutionary Biology Graduate Student Symposium: Cornell University, Ithaca, NY
1996 Guild of Rocky Mountain Population Biologists Annual Meeting: Colorado College Baca Campus, Crestone, CO
Review of Manuscripts
Australian Journal of Entomology
Biological Journal of the Linnean Society
Entomologia Experimentalis et Applicata
Global Change Biology
The Canadian Entomologist
The Great Lakes Entomologist
Review of Proposals
2009 Panelist, NSF Graduate Research Fellowship Program, Ecology Panel
2008 External Referee, Netherlands Organization for Scientific Research (Dutch Research Council), Council for Earth and Life Sciences
2002-04 Panelist, Kieckhefer Adirondack Fellowship, Cornell University
2002-04 Panelist, Andrew W. Mellon Fund, Cornell University
2008-09 Classroom presentations for >500 2nd graders to enhance science curriculum on insect life cycles at Rosemary Hills Elementary, Garrett Park Elementary and Forest Knolls Elementary, part of Montgomery County Public Schools, Maryland.
2008-09 Judge for Buell and Braun awards at the Ecological Society of America Annual Meetings: Milwaukee, WI; Albuquerque NM
2000-05 Graduate Representative at Faculty Meetings, Cornell Univeristy
1999-00 Co-President, Ecology and Evolutionary Biology Graduate Student Association
1999-00 Graduate Student Representative, Cornell University College of Agriculture and Life Sciences’ Task Force for Improvement of the Graduate Teaching Assistant Experience
Last Updated February 3, 2010
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