Weed Ecology Lab


Pennisetum setaceum



Arundo donax



Brassica tournefortii



Cynara cardunculus

Holt Lab Members

Dr. Jodie Holt

There's nowhere near enough room on this page to describe all the exciting things we do in the lab!

Instead, follow this link to my personal webpage.



Staff Research Associate

Dr. Rana Tayyar

I joined Dr. Holt's Laboratory in January 1998 as the lab SRA. I can sum up my years of service so far as enriching, productive and fun. My duties involve managing the lab and its personnel.

My training in plant genetics has allowed me to incorporate some genetic aspects into the ecology and physiology research of the invasive species studied in our lab. I have completed genetic analysis on Cyperus species and on Arundo donax. I am currently working on some seed ecology aspects of three Brassica species (mainly relating to seed germination). In addition, I am studying genetic variation within and among patches of Cynara cardunculus (artichoke thistle) plants from Crystal Cove State Park (Laguna Beach, CA). The latter study is a part of a bigger project underway in the lab.

I enjoy cooking, quilting and just recently knitting.


Postdoctoral Researchers and Other Professionals  

Dr. Virginia (Ginger) White

For my graduate work, I studied the ecophysiology of Cynara cardunculus, artichoke thistle. My focus was on the establishment phase of an invasion, so I focused primarily on seedlings. From my field sites, I could see the Pacific Ocean and a few rattlesnakes.

My postdoctoral research focuses on Arundo donax control and management. Currently, I have a 'spray' study underway to better control small clumps of Arundo within a native species matrix.

The remainder of my time is spent teaching General Biology, Population and Organismal Biology, and Health Science at Riverside Community College.

I love to cook, so I spend my free time gardening, running and practicing yoga. For more information, please visit my website.


Graduate Students  


Lynn Wihbey Sweet

Since entering UCR (after wind-dispersing in from the East Coast), I have been developing my research ideas in several areas of weed ecology. First, I am indulging my long-standing interest in mapping and biogeography through work on a Lab project using a climate model to predict invasive plant distributions.
I am also interested in invasive species strategy and community invasibility. To that end, I plan to look at abiotic and biotic factors influencing the distribution and spread of fountaingrass, Pennisetum setaceum in the arid southwestern U.S.
When I am not searching for spatial data or finding far-flung plant localities using Google Earth, I enjoy hiking, photography, “botanizing,” and mountain biking.


Kai Palenscar

As part of my dissertation research I will conduct experiments on giant reed (Arundo donax).  Since receiving my B.S. degree from California State University San Marcos I worked for several years as a private consultant on restoration projects in Southern California.  This experience fueled my desire to refine the techniques in use today within the field of native habitat restoration. My research will be relevant to practical questions and concerns of land managers when designing restoration strategies for riparian systems impacted by giant reed.


Janet Garcia

My research focuses on the population genetics of Cynara cardunculus, which includes three subspecies: cultivated or globe artichoke, cultivated cardoon, and the weedy artichoke thistle, sometimes known as wild cardoon. Artichoke thistle is an extremely invasive weed on three continents outside of its indigenous range. I am interested in tracking the history of invasion of this weed into California and the consequences of hybridization either through newly opened avenues of gene flow between previously geographically separated populations or between subspecies. Through the use of molecular marker studies, a common garden study, and hybridization experiments, we hope to determine if these populations resulted from a hybridization event(s) or were introduced directly either singly or multiple times. Understanding the routes by which such unwelcome visitors are able to enter a community and take hold allows us to better understand how to prevent such introductions in the future. Understanding spread patterns and consequences of gene flow amongst introduced populations are also important for the proper assessment of the most efficient use of resources when planning eradication or control efforts.

In my free time I like to hang out with my family (including my kitties). I garden as much as possible, and hike when time and weather permit. I enjoy blues and bluegrass, jazz and classic rock. I have a mild shoe addiction.



Robin Marusha

My research interests are in plant invasion ecology, particularly invasion mechanisms in wildland ecosystems. In the past for my Master’s research, I worked with Dr. Holt on the seed dispersal and seedling establishment patterns of Cynara cardunculus, focusing on the effects of adults on seedlings in spatial relationships. Currently, as a PhD student, I am working on the biology and phenology of Brassica tournefortii in comparison with other invasive mustards and desert native species. I have also worked on coastal sage scrub restoration with Dr. Edie Allen and worked with the statewide weed manaegement program at the CA Dept. of Food and Ag. with Steve Schoenig, My goal in research is to link ecological theory with practical application.. Mostly, though, I think weeds are some of the coolest organisms on the planet and I just can't get enough of them! Aside from the fascinating world of invasive species, I’m the Academic Affairs Officer for CNAS and love to play with the Ultimate Frisbee club here on campus. I’m involved with the California Invasive Plant Council as a local speaker and representative. I’d call myself a foodie, and I love outdoor and travel adventures of all kinds!  

  Lab Assistants  

Polly Johnson

I graduated from Utah State University with a B.S. in Biology.  In college I focused my reserach on ecological physiology of range species. Before the Holt lab I worked for sometime with the San Pitch River Watershed Group on conserving natural resources and improving water quality. I also helped landowners recieve grant funding for restoration projects. In the Holt lab I work with Ginger on the Arundo donax managment project. I absolutely love field work and being in the greenhouse. In my spare time I enjoy swimming, playing all sports, and pretty much doing anything outsite (hiking, biking, camping, skiing, boating, etc.) I have learned a lot from the Holt lab so far, especially how to cook some great foods!


Sarah Otter

As a student at Riverside City College I took Biology from Ginger and learned about the Holt lab. Now I am a Lab Assistant in the lab and help on many different projects.


Past Lab Members

Holly Wanamaker

I graduated with a B.S. in Botany from UC Riverside.  I worked on several different projects in the Holt lab. I am currently now working in Boulder, Colorado in the Parks and Recreation Department as an Integrated Pest Management and Conservation Tech. I help control invasive weeds and also monitor several animal species.


Lauren Quinn

I graduated with my PhD from Dr. Holt's lab in 2006. My research focused on the dependence of Arundo donax establishment on community dynamics and abiotic conditions. My goal was to better inform restoration and other management efforts for this invasive species. I am now doing postdoctoral work in Australia.

My other interests include yoga, camping and hiking, and hanging out with my dog and other friends.