Former Lab Members

Post Docs

Rebecca Borchering (2021 – 2022)

1Rebecca is a postdoctoral researcher in the Department of Biology and joined the Shea lab in June 2020. She earned a PhD in Mathematics from the University of Florida in May 2017, focusing on stochastic processes of invasion and extinction, with particular applications for seasonal rabies virus dynamics. She previously held postdoctoral positions at the Emerging Pathogens Institute and Department of Biology at the University of Florida and at the Odum School of Ecology at the University of Georgia. Her research interests center around infectious disease modeling and public health applications. She is interested in the dynamics of co-circulating pathogens and her previous work includes investigating the effects of the 2015/2016 Zika epidemic in Latin America on endemic dengue dynamics and the emergence of novel influenza B viruses in the United States. In the Shea lab, she helps lead multiple modeling efforts to inform decision support in the face of uncertainty during the COVID-19 pandemic. She works on both the Multiple Models for Outbreak Decision Support (MMODS) and COVID-19 Scenario Modeling Hub projects.

For more info, please visit: 

Damie Pak (2021)

1I am a post-doc in the Department of Biology who is interested in many different areas across theoretical ecology. However, my passion lies with insects and their dynamics!  I earned my PhD with Ottar Bjornstad at Penn State where I explored different facets of biological timing across many different systems. For example, my dissertation looked into the  tick community of Pennsylvania, the neotropical rainforests of South America, and the lepidopteran pests of the Mid-Atlantic apple farms. Now, I am interested in exploring how uncertainty influences the best management action amidst the Covid-19 pandemic.

Tiffany Bogich (2003 – 2006, 2020 – 2021)

TiffanyprofileI started as an Honors student and then became a graduate student through the IUG program and completed my MSc in the Shea Lab in August 2006. My work in the Shea Lab was focused on the optimization of monitoring and management decisions for invasive species, using the invasion of the gypsy moth Lymantria dispar into North America as a case study. Currently, I am in my third year as a PhD student in the Conservation Science Group at the University of Cambridge, funded by the Bill & Melinda Gates Foundation. My work is centered on gathering global, regional, and empirical evidence for the Species Area Relationship as used to predict species’ extinction from habitat loss and then developing a mechanistic model to explain the relationship of habitat loss to extinction risk across spatial scales. Tiffany returned to the Shea lab in 2020 for MMODS and COVID-19 Scenario Modeling Hub.

Shouli Li (2015 – 2019)

My major research interests lie in quantitative ecology and environmental decision-making. I combine modeling and/or experimental approaches to understand and predict the Shouli Liresponse of populations to rapidly changing environmental conditions, as well as to provide support for environmental decisions in the areas of desert restoration, invasive species management and epidemic intervention. I am currently working on Ebola modelling and management.  By using simulations of alternative intervention strategies under different models, I am trying to provide insights into how model uncertainties could affect decision-making, and how this would differ when the management objectives are different.  During my previous researches at Turku University and Utrecht University, I combined demographic modeling, molecular markers, large scale filed experiments and common garden approaches to explore the factors driving the population establishment of invasive plants and the population dynamics of desert shrubs in response to different environmental stresses and disturbances.

Adam Miller (2009 – 2012, 2017 – 2020)

AdamprofileI am interested in a broad range of topics in theoretical ecology. Generally speaking, I try to understand community dynamics based upon the interactions between species’ life-history traits and environmental factors. Though the biological nature of these interactions varies quite widely across different communities and organisms, we often find strong commonalities in the mathematical descriptions of the processes.

Ecological disturbance exerts a strong influence in many communities, and is often used as a tool for conservation and management.  Thus, understanding how species respond to disturbance, and what consequences are entailed has the potential to inform management practice, as well as to explain the behavior of different communities from a unified theoretical perspective.

Adam periodically works with the Shea lab again on disturbance related research.

Research keywords: community ecology, mechanisms of diversity maintenance, control of invasive species, spatial ecology, disturbance ecology, environmental variation, competitive coexistence.

Chris Baker (2016)

My research is aboutparents house.JPG developing mathematical models of biological systems to help improve the way that we manage them. Here at Penn State, I am working on management strategies for treating drug-resistant diseases. Before moving to Penn State I completed a BSc and a MSc in applied mathematics, followed by a PhD in the Quantitative and Applied Ecology group, all at the University of Melbourne, Australia. I have worked on a range of problems, including in optimising invasive species management and predicting how management decisions will affect networks interacting species.

Dr. Baker left the lab to take up a prestigious Norris fellowship in Australia.

Laura Russo (2015 – 2017)

laurarprofileI study mutualistic interactions, particularly those between pollinators and plants. In a community context, these interactions form networks, the structure of which is a healthy area of research. Beyond these network representations, pollination services are increasingly important, and increasingly threatened, in agroecosystems. Much of my work focuses on shifting our reliance away from the domesticated honeybee toward communities of many species of wild bees. I’m broadly interested in community structure, mutualisms, coevolution, and ecosystem services. I did my graduate work at Penn State and a postdoc at Cornell University with Bryan Danforth before returning to Penn State for another postdoc.”

Dr. Russo gained a Marie Curie Fellowship to work at Trinity College, Dublin.  She will start at UT Knoxville in March 2019 as an Assistant Professor.

Yun Tao (2015 – 2017)

I am a post-doctesttoral researcher in the Center for Infectious Disease Dynamics. My work consists of developing behavioral models of vaccination strategies for the management of foot-and-mouth disease (FMD) in the United States. I completed my PhD with Alan Hastings in theoretical ecology at the University of California, Davis. My research interests combine animal behavior, population ecology, and epidemiology, with a focus on predicting the emergence of complex spatiotemporal patterns stemming from movement patterns. My past experience also includes modeling metapopulation dynamics at the University of Helsinki with Otso Ovaskainen and Ilkka Hanski. I am currently in collaboration with researchers at EcoHealth Alliance to investigate the risks and management options of Rift Valley Fever based on the seasonal home range patterns of wild and domestic ungulates.

Will Probert (2013 – 2015)

will-croppedI’m a post-doctoral researcher in the Center for Infectious Disease Dynamics at the Pennsylvania State University.

My research focuses on the development of models of spread of foot and mouth disease (FMD) in the United States, and associated mathematical optimization methods for the control of an FMD outbreak.

I was previously based in Toulouse, France, working with collaborators at INRA-Toulouse. We developed tools from the optimization and decision-theoretic literature for use in the conservation of biodiversity and natural resource management. My PhD supervisors were Hugh Possingham, Peter Baxter, and Anthony Richardson at the Centre of Excellence for Environmental Decisions, Brisbane.

Colin Campbell (2012 – 2015)

colinprofileI study how relatively simple interactions give rise to intricate system-level behavior: only through understanding how a system functions is it possible to intelligently predict or influence its behavior. While I study a range of biological systems, my work in the Shea lab primarily focuses upon ecological networks formed by plants and their pollinators. Understanding these systems is critically important: the ongoing, global decline of pollinators has direct implications on human agriculture. In some of our most recent work, we have sought to understand how ecological communities form and how they respond to perturbations, the structure of at-risk ecological communities, which species within at-risk communities are critical to their stability, and the effects of various intervention strategies aimed at preventing community collapse.

Colin joined the faculty of the Physics Department at Washington College, MD in 2015.

Alessandra Marins (2012 – 2013)

AleMarinsI’m broadly interested in social insects’ behavior and ecology. Specifically, I currently research termite-termite associations, where different termite species can co-occur within the same mound. Since there is no reliable protocol to work with termite mound builders in lab condition, I’ve been studying their interactions indirectly by accessing which factors affect mound invasion by termite guests.

My research project is three folded: I’m using empirical data to investigate how the biotic and abiotic factors influence the guest species community inside a mound. Besides, using literature review I’m accessing if the association network between termite host and termite guest are mainly mutualistic or antagonistic (in collaboration with Colin Campbell and Laura Russo). Also using published data, I’m investigating how biotic and abiotic factors affect cohabitation inside termite mound in a broad geographical scale.

Suann Yang (2006 – 2011)

suannprofileMy research is centered on the intersection between evolutionary ecology and community ecology, especially in the context of colonization. This interest is exemplified in my dissertation research, where I focused on the consequences of community context for the colonization of Vaccinium membranaceum(black huckleberry) at Mount St. Helens. In the Shea lab, which I joined in September 2006, I am interested in pollinator-mediated interactions of Carduus nutans and Carduus acanthoides. For insect-pollinated plants such as these, pollinator foraging behavior can have important demographic and population genetic consequences.

Eelke Jongejans (2004 – 2008)

EelkeprofileMy main interests are in processes at the plant level, and their impact on population dynamics, both at the local and at the landscape scale. In plant ecology research I prefer a combination of field, experimental and modeling studies. In the Shea lab I studied the spatial population dynamics of invasive thistles in both their native range and different invaded ranges, using local and spatial matrix models and integral projection models. I am currently conducting this type of studies at the Radboud University Nijmegen, while continuing to be involved in several projects in the Shea lab.

Eelke is now a Professor in the Department of Animal Ecology and Ecophysiology at Radboud University Nijmegen in the Netherlands.

Olav Skarpaas (2003 – 2005)

olavprofileI am interested in population ecological theory and its application to environmental management problems. Three of the major man-made environmental problems of our time are climate change, land use change and biological invasions. I do research that is relevant to all three (see below), but my main focus as a postdoc in the Shea lab (2003 – 2005) was invasion. Ecological theory is still largely unable to predict the speed and spatial patterns of spread of invasive species, partly because of insufficient knowledge about the shapes of dispersal kernels. In collaboration with Dr. Shea (and others) I am developing models to predict the rates and patterns of spread of the two invasive thistles Carduus nutans and C. acanthoides on a range of spatial scales. The empirical basis for the modeling is an array of population biological studies conducted by the Shea lab. I am responsible for wind dispersal studies aimed at measuring and modeling dispersal kernels.

I am also interested in the ‘inverse’ of the invasion problem: conservation of threatened species. In previous (M.S. and PhD) and ongoing research I investigate the links between habitats and vital rates in lab and field studies, and model the local population and metapopulation dynamics of rare plant species in fragmented landscapes. Most of this work (carried out in collaboration with people at the Universities of Oslo and Tromsø, Norway, and the Norwegian Institute of Nature Research) is focused on two declining plant species in Norway, Mertensia maritima and Crepis praemorsa. These species are affected by climate change (M. maritima), land use change (C. praemorsa), and their interaction.
Olav moved to a postdoc at the University of Oslo, Norway, and now works for the Natural History Museum in Norway. He is still actively involved in research in the Shea lab.

Graduate Students

Joe Keller (2012 – 2019)


I am working to better understand how climate affects interactions between plants and herbivores. My work focuses on tracking the seasonal timing of life history events for the invasive thistle Carduus nutans and the biological control weevil Rhinocyllus conicus. I use information gathered from field experiments and from detailed observations of naturally occurring populations to find out how climate affects seasonal synchrony between the two species and to examine how synchrony affects population dynamics.

Amalie McKee (2011 – 2016)

Snapshot_20121018_4I am broadly interested in theoretical disease ecology and disease management.  Both disease dynamics and disease management depend on population parameters, such as age structure.  Much of disease management is done at a broad scale, with individuals and organizations making public health recommendations on the country scale.  However, relatively small changes in population parameters, such as age structure or disease history, can make huge differences in the effectiveness of these recommendations.  I study how optimal disease management strategy depends on these population parameters.  I am particularly interested in measles vaccine policy, with regard to how the timing of routine immunizations interacts with age structure and maternal acquired immunity.

Dr. McKee went to on postdocs in CIDD with Matt Ferrari and is now working at the University of New Mexico with Helen Wearing.

Britta Teller (2008 – 2014)

brittaprofilePassively dispersed species face both risks and rewards when offspring move across a landscape. The probability that any particular offspring survives depends on the dispersal characteristics of the maternal individual and the dispersing offspring, and the distribution of suitable habitat in the landscape. As a PhD student in the Shea lab, I am primarily interested in individual dispersal traits and population spread through heterogeneous environments. Empirically, I examine how individuals’ traits change in response to stressors in the field, and then I use models to understand the ecological consequences of these changes for demography and spread. While I currently focus on the invasive species, Carduus nutans, in the future I hope to use this research to improve our general understanding of how dispersal contributes to individual fitness, population demography, and population spread in both rare and invasive species.

Britta became an assistant teaching professor at Penn State before starting her own business, Stellar Floors!

Laura Russo (2008 – 2013)

Laura was a graduate student in the Shea lab, but also came back as a postdoc!  See the postdoc section for more information.

Rui Zhang (2006 – 2011)

ruiprofileI study biological invasions in the context of disturbance and climate change. As a case study to examine the relationship between disturbance and invasions, one of my projects focuses on the effects of mowing, a commonly used management tool and a pulse disturbance, on two invasive thistles, Carduus nutans and C. acanthoides. My results show that different aspects of a disturbance (e.g. frequency, intensity, and timing) can interact with each other to induce complex responses. Another recent project is to explore how climate change, such as warming and increased precipitation, affect the phenology, growth and reproduction of the two invasive species.

Rui graduated in fall 2011 and moved to a postdoc with Elizabeth Crone at Harvard Forest.  She now works for Google!

Jessica Peterson-Smith (2004 – 2005)

JessicaprofileMy research interests are focused on plant community dynamics, scaling up to ecosystem processes and down to population ecology. I spent 1 year in the Shea lab (September 2004 – July 2005). I am interested in using community ecology theory and modeling techniques to study the establishment and success of invasive thistles. Additionally, I am interested in the link between the spread of invasive species and changing environmental regimes and plant community composition resulting from land-use transformations and disturbance. My previous research work for my M.S. degree included studies of natural plant communities in tidal freshwater wetlands, specifically investigating the composition, spatial distribution, and controls on germination of seeds in the soil seed bank, as well as factors explaining varying levels of species richness in these communities. Most recently, I was employed as a project manager with a large research team based at Penn State testing a wetland classification and functional assessment scheme in forested wetlands of the Appalachian Mountains ranging from Virginia to New York.

Jessica Peterson-Smith is now a plant ecology technician for Boulder County Parks and Open Space, working on vegetation mapping, ecological restoration and native seed collection.

Mike Rubbo (2004)

mikeprofileMy research focuses on understanding the impact of variations in system level processes on community dynamics. Specifically, I am interested in the influence of variations in the input of allochthonous carbon to food webs that are based primarily on detrital pathways. In order to assess the importance of external inputs of carbon and nutrients to communities, I utilize temporary forest ponds as a model system. These ponds are heterotrophic systems that rely principally on leaf-litter from the over-story vegetation for the major input of organic carbon. Ephemeral ponds are used primarily as breeding sites for amphibians and invertebrates. The amphibians that breed in these ponds exhibit complex life cycles (CLCs), with juveniles emigrating from natal ponds shortly after metamorphosis. The successful recruitment of juveniles from these ponds is extremely stochastic. I am interested in how variations in factors such as the inputs of carbon and nutrients influence species interactions, and ultimately amphibian recruitment. If the performance of a species’ is altered in concert with a change in one or more of these factors, this species’ fitness may be altered through such means as a shift in competitive ability, or through a change in its vulnerability to predators or pathogens.

Mike moved to Virginia Tech as a postdoc with Dr. Lisa Belden and works now for an environmental consultancy.

Emily Rauschert (2001 – 2006)

OLYMPUS DIGITAL CAMERAI am focusing on understanding the mechanisms behind plant species invasion, and how this can lead to improved management of highly invaded systems. I am also interested in the role that humans play in the spread of invasive species. My work aims to combine modeling, experimental and observational techniques.

I am currently pursuing a post-doctoral position with Dave Mortensen in the Weed Ecology Lab in the Department of Crop and Soil Sciences at Penn State. We are focusing on quantifying the mechanisms behind the rapid invasion of an invasive grass, Microstegium vimineum. Evidence from dispersal experiments clearly demonstrates that Microstegium spreads very slowly unaided; clearly human-mediated dispersal is largely driving the invasion of this species. We are focusing our initial efforts on the role that road maintenance has on spreading Microstegium propagules. This research, which is in collaboration with the Center for Dirt and Gravel Road Studies, has been funded by the National Research Initiative of the USDA Cooperative State Research, Education and Extension Service, grant # 2007-02917. I recently finished modeling the spatial spread ofMicrostegium, using data from a three year experiment on establishment in different habitats. I am also working with data from a large-scale survey of multiple invasive species in a forest along the Pennsylvania-Maryland boarder. The aim of this work is to identify the factors associated with invasive species presence, and then to predict areas where invasive species are more likely to occur, in order to focus management efforts.

My dissertation work focused on interactions between Carduus nutans and C. acanthoides, two congeneric invasive thistle species. It was hypothesized that their observed spatial segregation was due to interspecific competition. I developed spatially-explicit simulation models of competitive interactions between these species at both the landscape and the field levels, to explore the range of behaviors predicted, and compared these to the results of a series of response-surface experiments on competition between these species. In order to understand natural patterns of co-occurrence, I quantified the thistle distribution patterns at two resolutions: the regional level in an area of overlap, and the field level in four fields of natural co-occurrence. I examined their interactions with the existing vegetation in two ways: by quantifying their vegetative associations in four fields of co-occurrence, and by experimentally examining their germination and establishment response to microsite characteristics. Combining the results from these different approaches demonstrates that the observed distributional pattern is unlikely to be due to interactions between thistle species, and is more likely due to their spread history and their difficulty competing with established species.

Katriona Shea, Stephen Roxburgh and I reviewed the mechanisms underlying the intermediate disturbance hypothesis: Shea, K., S. H. Roxburgh and E. S. J. Rauschert (2004). “Moving from pattern to process: coexistence mechanisms under intermediate disturbance regimes.” Ecology Letters 7(6): 491-508.

Emily graduated in 2006, moved to a postdoc in Deave Mortensen’s lab at PSU, spent spring 2012 on a Fulbright in Hungary, is now an Assistant Professor at Cleveland State University.

Zeynep Sezen (2001 – 2003)

ZeynepprofileAs a graduate student in the Shea lab, I am interested in the effect of the local spatial distribution of the invasive musk thistle Carduus nutans on the population dynamics of its biocontrol agent Rhinocyllus conicus. This seed feeding weevil has commonly been used to control non-native thistles such as musk thistle and plumeless thistle with variable success. The weevil has also been reported to establish on non-target native thistles, therefore these alternative hosts may be a possible reason for the lack of success in some control programs. Initially, I am looking to see how the patch size and density of the thistles affect the oviposition and adult density of the weevil. Through a better understanding of the patch preference I hope to further identify factors that limit or facilitate weevil establishment. I am also interested in the link between community diversity and invasions and have a small side project looking to see how the presence or absence of the musk thistle relates to differences in community composition.

Masters Students

Katie Myers Marchetto (2006 – 2008)

KatieprofileI started in the Shea Lab as a National Science Foundation (NSF) Research Experiences for Undergraduates (REU) student in the summer of 2006, and stayed to do a Masters as part of the Schreyer Honors College Integrated Undergraduate Graduate Program (IUG).  My Master’s thesis, “Abiotic and biotic factors affecting seed release and dispersal of the invasive thistles Carduus nutans and Carduus acanthoides,” concerns the effects that wind and weather, as well as florivory by the biocontrol agent Rhinocyllus conicus, have on seed release and seed dispersal.  In addition, one chapter in my thesis addresses potential biases in observed seed dispersal capacity due to storage duration or compression caused by storage or shipment.

Tiffany Bogich (2003 – 2006)

Tiffany was an honors and masters student in the Shea lab. She also came back as a postdoc!  See the post doc section for more information.


Melanie Northrup (2003 – 2004)

MelanieprofileI joined the Shea lab in July of 2003, taking over for Emily Phillips as the senior research technician. I manage Dr. Katriona Shea’s on-going experiment involving two invasive thistle species (Carduus spp.). I also coordinate the hiring and scheduling of activities of a team of undergraduate student workers. I am interested in learning more about this facet of ecology and experimental design of large-scale experiments. I will also be involved with some of the statistical analyses associated with the project.

Before joining the Shea lab, I completed my M.S. in Forest Management here at Penn State. I developed a classification scheme of forest understory communities and focused on the relationships between these communities and oak regeneration. I am currently in the process of revising a manuscript of my work for publication. I will soon start work on a project for the Forest Service in Pennsylvania, in which I will analyze statewide forest inventory data in collaboration with a PhD student in the Forestry Department at Penn State.

Melanie moved to the lab of Dr. Claus Holzapfel at Rutgers.

Emily Leichtman (née Phillips) (2002 – 2003)

emily2profileI began working in the Shea lab in the summer of 2002 (till July 2003), taking over from the unparalleled Teresina Bailey (see above) as senior technician. I manage several of Dr. Shea’s on-going experiments, coordinate the activities of our undergraduate assistants and perform a variety of other tasks in the field and in the lab. I am eager to gain more experience with terrestrial ecology and with modeling and have initiated a project examining the effects of Carduus nutans seed size on germination time. In collaboration with grad student Zeynep Sezen, I am also planning a project to model C. nutans seed head production as it relates to plant size at the beginning of the spring growing season.

Before joining the Shea lab, I completed my M.S. in Ecology here at Penn State. I am currently preparing a manuscript of my masters work, a study of fish populations as indicators of acidified streams, for publication. In general, I am interested in the response of populations and communities to disturbance.

Emily now works for NSF.

Teresina Bailey (2001 – 2002)

TeresinaprofileI was the first technician in the Shea lab (June 2001-September 2002). My interests are Geography of Nutrition and Urban Poverty (my work-in-progress Masters thesis), urban gardening, herbal medicine, and a host of earth sciences related topics.  I am pursuing a career in grassroots community organizing, social activism, and music.

Teresina later worked for the Urban IPM group based in the Department of Entomology.

Honors Students

Trine Ready (2018 – 2019) 

Trine studied the diversity – disturbance relationship and joined the Peace Corps after graduation.

Ishan Phadke (2016 – 2019)

Ishan analyzed how changes in the health status of healthcare workers affects epidemic outcomes. Ishan was recruited via the Millenium Scholars Program and also worked in our lab through an applied mathematics REU. He additionally gained a HHMI award in summer 2016 for his housing during this project. He worked on his Honors thesis research the entire time he was associated with my lab. On graduating he started his PhD in Economics at University of North Carolina Chapel Hill.

Jon Saperstein (2011 – 2014)

Jon joined the Shea lab through the NASA Spacegrant FURP program.  He studied how environmental conditions affects seed terminal velocities in a wind-dispersed invasive plant.

Andrew Garrison (2011 – 2013)

Andy joined my lab on an NSF-REU award in summer 2011, and has remained in my lab to conduct his Honors research, gaining a second REU in summer 2012.

Amy Leib (2007 – 2009)

amyprofileAs an undergraduate student in the Shea Lab, I have spent the past year (Spring 2006 through Fall 2007) working on other lab members’ projects. This semester (Spring 2007), I am starting to work on my own project that could potentially develop into my honors thesis. I am a sophomore majoring in Biology and minoring in History and am looking forward to putting a project together that will allow me to focus on both of these interests. I would like to compile more information about the history ofCarduus nutans in North America over the past 160 years. Specifically I will try to resolve whether C. nutans was introduced in one location or in several locations over different periods of time. In addition, I would like to determine whether the history of the invasion of C. nutans is correlated to events in human development in North America.

Amy graduated in 2009 and went to Medical School at Hershey.

Leah Ruth (2006 – 2007)

leahprofileI am a second year Honors and WISER student. I am majoring in Horticultural Science with a minor in Biology. I worked on other lab member’s projects during the spring semester ’06, and this fall I am starting a project of my own. I will most likely be working on a Carduus nutans and C. acanthoidessoil seed bank project and/or a leaf nutrient analysis project that studies leaves produced by thistles with varying degrees of stress. I am also hoping to spend the summer ’07 semester in State College, potentially working on my project and developing my thesis paper.

Leah graduated in 2009 and went to work for the USDA for four years.  Now she is an assistant scientist with Ball Helix in Chicago, working in their plant pathology lab.

Laura Warg (2005 – 2008)

laura2profileLaura’s study aimed to use genetic information to track the invasion of Carduus nutans and to relate that information to invasion patterns proposed by existing scientific literature. Samples from across the United States, as well as the UK, Netherlands, and France, have been collected and cultivated to yield plant material from both the native and invaded ranges. In a partnership with the dePamphilis lab, she conducted a genetic study of variable regions in C. nutans DNA. This study involves isolated DNA from leaf samples, locating polymorphic regions, amplifying these regions, and then sequencing them. The sequences will help to clarify the invasion geography and timeline of C. nutans, as well as supplement a larger phenotypic study being conducted by the Shea lab.

Originally Laura was interested in field work, but became keener on the genetic studies. Her field research in the Shea lab focused upon the effect that insect herbivory has upon thistle seedlings. Field studies in Fall 2005 involving both C. nutans and C. acanthoides were designed to provide information on the extent of insect damage by comparing insecticide treated plants and non-insecticide treated plants. The aim was to replicate this experiment, as well as add a study of the insects present in the area. With the use of pitfall traps, the species feeding upon the thistle seedlings could be captured and identified. Together these two investigations should add some insight into this early period of the thistle life cycle.

Laura Warg moved to a lab tech position at the National Jewish in Colorado.   She started in the MD/PhD program at the University of Colorado in fall 2011.

Lewis Grove (2004 – 2007)

LewisprofileMy Honors research in the Shea lab consisted of data analysis of a data set of avian census results from the Kurupukari region of Guyana. The data was collected in 1992 by Dr. Shea and associates. The data was summarized and analyzed using standard survey technique statistical methods. This represents a comprehensive and unique data set for the region and can serve as the basis for future expeditions.

Eddie Silverman (2004 – 2006)

eddieprofileAs an Honors student here at Penn State, I started working in the Shea lab in the Fall of 2004. I have worked most closely with Olav Skarpaas. The first chapter of my thesis will focus on the relationships between seed characteristics, seed dispersal, and seed germination rates. In the future I will plan a larger project to quantify the effect of animal feeding on the thistles both as seeds and seedlings. Little is known about what happens to seeds between the time when they land on the ground to the time when they germinate. The summer of 2005 will be dedicated to this project, to hopefully fill in this gap of information in the thistle life cycle. It will be interesting to see the effect of seed predation on the thistle populations.

Eddie graduated in May 2006 and moved to medical school at George Washington University.

Gabrielle Hrycyshyn (2003 – 2004)

gabrielleprofileI worked with Dr. Hauge at the Hazleton campus on a mark-recapture study of 4 species of indigenous turtles (Pseudemys floridana penninsularisP. nelsoniSternotherus odoratus and S. minor minor) in a Wekiwa Springs State Park, Apopka, Florida. By the time I graduated in May 2004 I had gone to the site 6 times over 4 years. I used the data collected from these outings to determine the population size of these species, as well as estimates of growth, survivorship and recruitment. I worked with Dr. Shea here at University Park, utilizing the data collected in the field and estimates from the literature, to create a theoretical population matrix model for these species to see how their populations might respond to different water regimes. As the study site is within the Orlando metropolitan area there have been predictions that the water level in the spring will be halved within the next 20 years due to increased water consumption. The models provide a glimpse of what might occur and can hopefully be used to help managers who must keep these contingencies in mind.

I was a member of the Shea Lab for two years, working with the thistles. In addition to helping with the experimental plots, I have been fortunate to be involved in the research of most of the graduate students and postdoc: Emily, Zeynep and Olav. These experiences included GPS surveys, road surveys, thistle head dissections, seed dispersal studies and finding suitable field sites. My main lab-oriented task during the off-season was maintaining the lab reference library in EndNote, 3200 references and counting!

Gabby moved to start her Masters research at the University of Florida in Gainesville with Dr. Karen Bjorndal in summer 2004. She then worked for the National Science Foundation in D.C. for three years and now is a Biotech Paralegal at the patent law firm Sterne Kessler Goldstein and Fox.

Dave Ruggiero (2002 – 2004)

daveprofileMy honors thesis, examined the various environmental factors that affect the germination rate of our two thistle species (Carduus nutans and C. acanthoides). Earlier research has suggested that thistle germination is a strong predictor of an individual plant’s survival later on. If thistles can get established early on, they’re very difficult to eradicate. Therefore, I asked: what environmental factors are conducive to thistle germination, and what factors inhibit it. Specifically, my research examined the effects of:

  • Maternal habitat: do better conditions for the parent plant result in better seeds?
  • Soil moisture: does rainfall affect germination?
  • Microhabitat size: competition greatly influences germination success, but how close must competitors be before they have an impact?

Dave graduated in May 2004 with a B.S. in Environmental Resource Management, and honors (and a minor) in Biology. He moved to the graduate program at Stonybrook with Dr. Jessica Gurevitch in the fall of 2004.  He now works an organic vegetable farm back in PA.

Zebulon Bartels (2001 – 2003)

zebulonprofileI joined Dr. Shea’s lab in the summer of 2001 as a part-time research assistant. Through the summer and fall I helped Dr. Shea set up and run the invasive thistle experiment that continues to be the lab’s biggest project. In the fall of 2001 I began my own experiment within the lab. I tested the germination and growth of two similar thistle species on differing soil textures and under different watering regimes. Rather than using field soils of a few soil textural classes, as is commonly done for such tests, I attempted to formulate all twelve of the textural classes by mixing pure quantities of the three soil particle types: sand, silt, and clay. I used my work in Dr. Shea’s lab as a basis for writing my honors thesis.

I majored in Agroecosystems Science. After a volunteering for a year and going to graduate school I plan to return to my father’s farmland and start an organic farm, where I hope to do on farm research in cooperation with research institutions. Two of my main non-academic activities are classical guitar performance and activism for peace and justice.

Mike Allen (2001 – 2003)

mike2profileI studied spatial distribution patterns, particularly those of invasive species. My thesis project bolstered a personal interest in GIS technology and spatial mapping. Under Dr. Shea’s guidance, I developed a research project aimed at examining the distribution of our two study species, the musk and plumeless thistles, over a range of Pennsylvania and at broader spatial scales. My field research involved an intensive driving survey of a section of PA during the summer of 2002.

Mike graduated in May 2004 and moved to the PhD program at Illinois under Dr. Carla Caceres.  After graduating he then gained a Knauss Sea Grant Fellowship to Washington, DC. He then worked as a contractor for the National Oceanographic and Atmospheric Administration.  He now works as the Research and Education Coordinator for the University of Maryland Sea Grant College Program

Cyelee Kulkarni (2001 – 2003)

cyeleeprofileModeling of microparasite dynamics has been carried out for numerous systems, however, a detailed analysis through the use of mathematical and computer modeling of macroparasite systems is still relatively rare. The study of macroparasites, particularly helminthic parasites, including the class of digenic trematodes, is of great importance to both humans and amphibians since trematodes cause hundreds of cases of human diseases each year and have also been linked with developmental abnormalities in amphibians. Understanding the ecological dynamics of such systems should lead to improvements in management. In my thesis I developed and analyzed alternative life cycle models for a generic amphibian-trematode system, motivated by species complexes found in central Pennsylvania. Such systems usually include a second intermediate host (a snail) as well as a definitive host (e.g. a fox or snake) though often the definitive host is unknown.

Cyelee moved to graduate studies at the University of Pennsylvania.

See also: 

Tiffany Bogich was an Honors student who stayed to do a Masters and came back as a post doc. Read about her in the post doc section.

REU, WISER, FURP and MURE and other Independent Study Students

LaKeisha Wade (2021-2022)

1I am an undergraduate student majoring in Human Development and Family Studies and triple minoring in African American Studies, Biology and Woman Studies. I am a new member of the Shea lab joining in the summer of 2021 under REU. I have done previous work at the University of the Virgin Islands, researching environmental health issues such as food waste, waste disposal and disaster preparedness specifically for at risk groups like mothers, children and the homeless. I have a passion for researching women’s health especially in inner-city and low income neighborhoods. This will lead me to gaining a dual MPH/MD with a speciality in obstetrics and gynecology.

Jack Seifarth (2018 – 2019)

RJ Chandler (2015 – 2018)


I began working in the lab in January 2015, initially helping Joe Keller with data collection and entry related to his work with climate change and the invasive thistle, Carduus nutans. During fall 2015, I started my own experiment to further explore the link between terminal velocity and Carduus nutans dispersal characteristics, including seed weight and the dimensions of the pappus (hair-like projections). These effects are measured in response to different treatment conditions, and this research will help to answer questions on how to control the spread of this invasive thistle.

Ciara Hovis (2012 – 2015)
I started working in the Shea lab during the fall of 2012. Over the summer of 2013, I assisted Joe Keller with his field data collection in Harrisburg and at the Rock Springs Research site. During that time, I also began  an experiment using Carduus nutans to determine whether or not the timing and duration, intensity, frequency, or genetic composition of propagule pressures affects establishment of a species. This experiment is being done in collaboration with Dr. Ruth Hufbauer’s lab at the University of Colorado Boulder where they are conducting the same experiment, but with the beetle Tribolium castaneum.  I served as the lab manager in addition to finishing up my research before I graduate in May 2016. 

Spenser Bauman (2011)

Spenser joined my lab on an NSF-REU award in summer 2011 and has continued in the lab to work on disturbance simulation models.

Christina Nichol (2010 – 2011)Chrissyprofile

Chrissy joined the lab via the WISER program in 2010 in her first year and has been working with us on the insect communities associated with Carduus acanthoides ever since!

Daniel Reilly (2010)

Dan was a double major in Chemical Engineering and Mathematics, and was funded by an NSF Research Experience for Undergraduates (REU) award in the summer of 2010, working on models of disturbed communities.  He is now at graduate school in the Department of Chemical Engineering at the University of Illinois in Urbana-Champaign.  He works with Jennifer Lewis, on the assembly of hollow-shell polymer particles for encapsulation and controlled release of drugs or other chemicals.

Catherine Cruz-Ortiz (2009)

catherineprofileThe preliminary results from Rui’s climate change experiment suggest that predicted climate conditions produce advanced phenology and enhanced reproduction in invasive Carduus nutans. To supplement this experiment, Catherine worked on the comparison of phenology, growth and reproduction of natural populations of C. nutans across environmental gradients (esp. temperature and precipitation). Her REU project in summer 2009 involved interactions with volunteers who can help with data collection and field surveys at different study sites in Pennsylvania.

Mason Heberling (2009)

masonprofileAs an undergraduate, my academic and research interests have been dynamic. Broadly, these interests lie within community ecology and conservation biology. Through the Shea lab, I have become aware and very much fascinated by ecosystem properties and their role in plant invasion success. The proposed relationships between biodiversity and invasion are of particular interest. Most recently, I received REU funding, through which field data collection started in summer 2009. The general purpose of the experiment seeks to better understand various effects of thistle invasion on resident biodiversity. Data collation and analysis from this project are forthcoming. Following my spring 2010 graduation, I moved to graduate school at Syracuse.

Clayton Costa (2008)

claytonprofileClayton joined our lab for his last two semesters at Penn State, in 2008.  During this time, he worked with postdoc Suann Yang to develop a method to count pollen grains automatically, using an image analysis software program from NIH called ImageJ.  He used this method to quantify the number of pollen grains produced byCarduus nutans and C. acanthoides flower heads, information that will contribute to the plant-pollinator interaction research in our lab group.  Clayton’s paper was published in Annals of Botany in 2009!

Costa, C.M. and Yang, S. (2009) Counting pollen grains using a readily available, free image processing and analysis software. Annals of Botany 104: 1005-1010; doi:10.1093/aob/mcp186.

Richard Ashby (2008)richardprofile

Richard worked on a wide range of different projects in the lab, collaborating with graduate students and post-docs on invasive species research.

Matt Williams (2008)mattprofile

Matt worked in the Aerospace Engineering wind tunnel in summer 2008 on our PIV (Particle Image Velocimetry) study.

Kristin Gordon (2005 – 2006)

kristinprofileI am an undergraduate student member of the WISER program. I am working on a research project with Zeynep Sezen on the chemical ecology of Carduusthistles and their insect herbivore, the thistle head weevil. We hope to determine whether the volatiles released by thistles, as a result of weevil attack, attract other weevils and how weevils respond to these volatile chemicals in general. Although it is not within the scope of this study, we may discover whether or not a weevil releases pheromones that are detected by thistles and induce a response in the plant as well.

Nick Pedatella (2005)

nickprofileThe goal of my Summer 2005 study was to examine how changes in specific weather conditions, such as humidity, turbulence, and temperature effect the abscission process of Carduus acanthoidesand Carduus nutans within a controlledenvironment. How flower heads at different stages of development react will also be examined.

Rachel Evans (2004 – 2005)

rachelprofileRachel joined us through the WISER program. She was an Honors student majoring in Environmental Resource Management. Rachel spent a semester in Montpellier, France. She worked on policy issues in the lab and then did an Honors thesis elsewhere on law and the Endangered Species Act. She started at Harvard Law in Fall 2007.

Paul Chen (2004)

paulprofileTo optimize management of invasive Carduus thistles, seed dispersal needs to be quantified in natural populations. I tried to determine if mechanistic wind dispersal models could accurately predict seed dispersal patterns in natural populations. During the summer of 2004, seed traps were used to capture seeds at four different road sites and pastures. Wind data were collected from weather stations nearby. Now, empirical dispersal kernels and the outcome of mechanistic models will be compared

See also: 

Other Undergraduate Students

Jacob Janssen 

1I am an undergraduate student majoring in Immunology and Infectious Disease. I assisted with field research during the summer of 2021. I have obtained prior research/medical experience at the Penn State College of Medicine at Hershey Medical Center. I was able to observe over 27 healthcare fields, and gained knowledge on the following activities: trauma care, hematology/oncology, autopsies, and even neurosurgery. Two quarter rotations in radiology and pathology were also completed during my internship/co-op. Lastly, I was able to conduct some assisted research regarding Lyme disease, thyroid cancer, and concussions. I am ecstatic to explore more STEM topics during my remaining academic years and further on into the future. During the fall of 2021, I am planning to aid Penn State with a new research project regarding epidemiology and small cell variants. After receiving my Bachelor’s degree, I intend to pursue more experimentation and progress towards a PhD (possibly in endocrinology, rare diseases, or wherever life takes me). My biggest dream is to help as many people as I can through medicine, technology, and travel.

(as at Mar 2016)

Simone Adeshina, Julie Ali (Roshan Qureshi-Chishti), Heather Alt, Dino Arcuri, Megan Bailey, Oneeka Barker, Scott Barndt, Kevin Barry (moved to grad school at University of Maryland), Julie Barsic, Julia Beiter, Nathan Bendik (after some technician positions, Nate got his MS at UT Arlington where he studied molecular systematics of salamanders, and now works for the City of Austin as a salamander biologist), Thomas Bibby, Dan Bice, Garrett Boarts, Dan Bower, Owen Bowser, Brosi Bradley, Michelle Bretzius, Evin Brown, Alissa Buck, Brian Butala, Jeff Buterbaugh (went to Lock Haven University to train as a Physician’s Assistant), Paige Byrns, Christine Camacho, Abby Caporuscio, Shruti Chandra, Yihe Chen (went to a Masters at Columbia), Kathryn Christopher, Matt Clark, Clayton Costa, Stacy Crawford, Rich Dabundo, Shabina Dalal, Kaitlyn Dalsey, Zach Danek, Ashley D’Antonio (gained a Master’s Fellowship from the Department of Human Dimensions of Ecosystem Science and Management at Utah State University), Carrie Davila, Erin Dawood (attends Cytotechnology School at the University of Pittsburg Medical Center), Jane Delle Donna, Chris DeMarco, Renae DePierre, Zak DeWalt, Xiaoxo Ding, Xiying Ding, Elizabeth Dlugosz (joined the PhD program with Dean’s Distinguished Fellowship at UC Riverside), Sarah Eissler, William Fescemyer, Stacy Finke, Brock Fiorito, Jacob Fisher, Heather Fowler, Stephanie Freed (moved to MSc program in Biology at Villanova), Lyndsy Gazda, Julio Gomez, Feiyi (Faye) Guo, Emily Haner, Allison Harford, Rohan Hattangady, Ahmad Hasan, Soroosh Taleb Hashemi (moved to grad school at the Arizona College of Osteopathic Medicine), Nate Hautala, Dionne Heard, Mason Heberling (moved to graduate school at Syracuse), Daniel Henning, Amber Hoover (moved to position with Water Watch AmeriCorps, and now is in the grad program at Idaho State University), Mitch Hulderman, Matt Jennis (now in PhD program at Drexel), Brian Jones (joined the Peace Corps in Madagascar), Mara Seree Kasputis, Paul Kazanjian, Christine Konrad, Rachel Lambert, Sarah Landis, Elizabeth Larcom, Elizabeth Larimer (moved to grad school at Drexel University), Jennifer LaVanture, Sharon Lee, Andrea Leshak (received a $200 research grant for her work), Kimberly Love, Megan Lundgren, Kerry Lynott, Twiza Mambwe, Stephanie Martin, Brian Medford, John Mellon, Rebecca Mendenhall, Mike Miller (went to teacher training at Lock Haven University), Rebecca Miller, Steve Miller, Geo Montoya, James Morrow, Anna Nousek, Estelle Ntowe, Matt Olsen, Edward Owen, Saras Padmanabhan, Danielle Perkins, Rick Pongrance, Kimberly Poole, Nathaniel Poole, Katie Porreca, Javier Portocarrero, Nancy Rachlis, Ravi Rao, Adam Reese, Rachel Rihl, Jordyn Rivell, Justin Robinson, Phillipe Rouchon, Molly Sabol, Miles Saunders, Christina Saylor (became a Research Technician), Tommy Scharnitz, Brittany Schoenen, Stephen Selego, Liza Senic, Myers Shaiyen, Meg Sheehan, Aubrey Sherron, Daniel Shin, Maegen Simmonds, Brianne Smithonic (moved to the Ross University School of Veterinary Medicine), Pacifica Sommers (moved to a PhD in Ecology and Evolutionary Biology at U Arizona), EunGyo (Eunice) Song, Jacob Spivak, Carwyn Sposit (works at DuPont), Matt Stanton, Derek Stephan, Jordan Stone, Evan Stover, Allie Srebro, Rachel Stehouwer (now Visscher), Jennifer Stella, Maria Stevens (recipient of a Merck Scholarship), Caitlin Sullivan (moved to medical school at PCOM, Philadelphia), Aswin Kaushik Sundarakrishnan, Chelsea Sutherland, Benham Tabatabai, Sarah Terrill, Rahwa Tesfay, Lauren Thomas, Bryan Tom, James Tsou-Wong, Herschel Tubbs, Katelynd Vanness (now working at BIDMC, Harvard), Victoria Vella, Shehan Weeraman, Laura Wentzel, Adrianne Whitehair, Maggie Wilkens, Chad Wilson, Lyndsie Wszola, Jiali Yu, Yichi Zhang, Brooke Zlotshewer.

Honorary Lab Members

Riley Mummah

I apply value of information analysis to Ebola management, specifically the 2014 West African Ebola outbreak, for my honors thesis in biology. Structural and parametric uncertainties exist between and within models, making it challenging to quantitatively rank the utility of Rileyintervention tools. Without a formal method of comparison, policymakers are forced to subjectively decide which models should dictate decision-making.
Value of information (VOI) analysis, commonly used in economics, quantifies the extent to which decision-making is hampered by such uncertainties, thus providing guidance as to how to prioritize future information gathering. This research is done in collaboration with Ottar Bjørnstad, Matthew Ferrari, and Shouli Li.

Steve Conaway (2008 – 2016)

steveprofileI am a PhD candidate in the department of plant pathology, but the Shea lab plays a major role in much of my research. I studyPuccinia punctiformis, a fungal pathogen that is a potential biocontrol for Canada thistle, Cirsium arvense. I am working to develop novel techniques for infecting healthy patches and establishing epidemics to control Canada thistle on farm, roadside, riparian and conservation land.

The host range of P. punctiformis is restricted to Canada thistle and cannot be cultured on artificial media. I am exploring greenhouse propagation of infected thistle as a possible source of inoculum for biocontrol efforts. Topics in my biocontrol research such as: movement and spread of disease over time; aerial dispersal of spores; and the dynamics of invasive host populations, overlap with the work being done in the Shea lab.


Ann Saghatelyan

Ann helped us with our botanical surveys.


Please keep in touch and let us know what you are doing now! Let me know of recent information.