Westminster College
 Department of Biology


Dr. Ann E. Throckmorton

Professor of Biology

Areas of interest:
Population ecology, aquatic biology, biostatistics

(724) 946-7209

(724) 946-7791

Email address:

311 Hoyt Science Center

Department of Biology

Westminster College

New Wilmington, PA 16172   USA

Courses taught

Biology Capstone
Freshwater BIology

Foundations of Biology I
Foundations of Biology II
Foundations of Biology III

Concepts of Biology
Marine Biology

Population Ecology
Introduction to GIS
Tropical Ecology:  Kenya

Tropical Ecology: Nicaragua
Tropical Ecology: Australia
Tropical Ecology: Costa Rica

Tropical Ecology: Belize
Ecology of Hawai'i
Ecology of the Galapagos

Ecology of the Caribbean
Research Design and Analysis Problem Analysis in E.S.

Field Botany
Conservation Ecology

Honors Colloquium
Information Technology

Research interests

My current research focuses on the biology and ecology of insects.  I am particularly interested in host choice and how host quality affects the behavior, performance, and life history characteristics of individuals and how those factors in turn affect the distribution and abundance of the species involved in the interaction.

Goldenrod gall fly

The goldenrod gall fly, Surosta solidaginis, is a parasitoid that is commonly found inhabiting several species of goldenrods in this area.  The relationship begins in the late spring when a female gall fly lays her eggs on the stem of the goldenrod.  The egg hatches, and the larval fly burrows into the stem.  In reaction to the presence of the larva, the goldenrod produces a ball-shaped gall which encapsulates the insect.  Eventually, the fly becomes an adult, chews its way out of the gall, and flies away to mate and begin the cycle again.

This system is very complicated.  While it would make sense that the presence of the parasitoid would have detrimental effects on the goldenrod, that has not yet been shown to be true in many cases.   That could make an interesting study for someone interested in plant ecology.  There are also many possible studies involving host choice and predator avoidance.  The galls are almost always found in clumps (i.e., if one goldenrod plant has a gall, nearby plants almost always do too).  Is this because the plants in that area have characteristics that attract many females, or is it because the female gall flies can only fly a short distance and therefore deposit eggs on plants in a relatively small area?  A genetic analysis of population structure and diversity would reveal which is true.   The distribution of the galls may also be influenced by natural enemies (birds and beetles, which feed on the juicy larvae, and parasitoid wasps which lay their eggs inside the fly larvae, eventually killing them).  The abundance and activity of natural enemies is influenced by habitat and environmental factors, which could lead to a lot of interesting questions involving multiple species and various interacting factors.  Finally, goldenrod is attacked by several other species of parasitoids which could compete with the gall flies and affect their performance, distribution, and effect on their host plant.
Eurosta solidaginis
Goldenrod ball galls
both images, copyright Dr. Warren G. Abrahamson and Paul Heinrich

Goldenrod gall midge (Rhopalomyia solidaginis)

These parasitoid midges also attack goldenrod, often inhabiting the same plants as the goldenrod gall fly.  In this case, the female lays her eggs in a leaf bud.  This prevents the plant’s stem at that point from elongating.  However, it continues to produce leaves, which end up clustered at the top of the plant, producing structures called "bunch galls" or "flower gall.”  These clusters may become home to a diverse assemblage of arthropods, including spiders and other insects.  For this reason, the goldenrod gall midge may play an important role in structuring food webs for arthropod species in this area.   Compared to the goldenrod gall flies, much less is known about these parasitoids which means there are many potential studies that could be done simply determining important features of the species and its populations.   There is some indication that susceptibility to bunch galls is an inherited trait within populations of goldenrod.  Whether that’s true or not could be determined by careful analysis of gall distribution, possibly coupled with genetic analyses.

In addition, there is a gall-making moth, Gnorimoschema gallaesolidaginis, which may directly or indirectly interact with the gall flies and gall midges.  It creates elliptal galls that are easliy distinguished from spherical galls.  However, its life cycle is very different from Eurosta's.  The females oviposit in the fall and the eggs overwinter on leaves.  In the spring, the larvae hatch and burrow into the stem, at which time the galls begin to form.  It's not uncommon to see galls from all three species of gallmakers on one plant.

bunch gall caused by Rhopalomyia
copyright Hilton Pond Center

Nasonia vitripennis

These parasitoids are tiny wasps which lay their eggs inside of the pupae of various species of flies.  The eggs hatch out inside the host and the baby wasps kill and eat the developing flies.  Like many insects, these wasps are haplodiploid – the males develop from unfertilized eggs and the females develop from fertilized eggs.  The fascinating thing about these insects is that the female can decide whether to fertilize an egg or not, thereby altering the sex ratio of her offspring in response to conditions in the environment and quality of available resources.  Under certain conditions, she may choose to produce mostly female offspring, while under other conditions, male offspring may be favored.  In addition, under certain conditions the female may reject the hosts entirely, instead choosing to leave the habitat and search for hosts elsewhere.  Many studies could be designed to see how various factors (host quality, host density, presence of competition, presence of mates, different environmental conditions) affect the behavior of  female parasitoids and the sex of offspring they produce.
Nasonia vitripennis
copyright John H. Werren

Student research
  • Humphries, Karen.  Evaluating the effect of photoperiod on offspring sex ratio of the parasitoid wasp, Nasonia vitripennis Biology Capstone project, spring, 2010.
  • Noyes, Stephenie.  The effects of polyandry on adult fitness and offsrping performance in Callosobruchus maculatusBiology Capstone project, spring, 2010.
  • Divjak, Nick.  Temporal replacement of plankton in a temperate zone freshwater beaver pond.  Biology Capstone project, spring, 2009 through fall 2009.  Research completed and results presented at he Slippery Rock Watershed Coalition Symposium, December 4, 2009.  Honorable mention.  

  • Kellner, David.  The effect of host distribution and host density on the giving up time of the parasitoid wasp Nasonia.  Biology Capstone project, spring, 2009 through fall 2009.
  • Morales, Joseph.  The effects of micro-plastics on the feeding rate of cyclopoid copepod, Cyclops spp. Biology Capstone project, spring, 2009 through fall 2009.
  • Van Buren, Bonnie.  The effect of autumn leaf coloration on the number of eggs laid by aphids.  Biology Capstone project, spring, 2009 through fall 2009.
  • Divjak, Nick.  Effect of cadmium on host choice by a hemiparasitic plant, Cusuta gronovii.  Van Vranken Research Fellowship, summer, 2008. 
  • Kriley, Vanessa.  The productivity of passive treatment systems on acid mine drainage of Slippery Rock Creek. Biology capstone project, spring, 2008 through fall, 2008.  Research completed and results presented at the Slippery Rock Watershed Coalition Symposium, December 4, 2008.
  • Okert, Amber.  The effectiveness of a passive treatment system for a western Pennsylvania stream affected by acid mine drainage.  Biology capstone project, spring, 2008 through fall, 2008.  Research completed and results presented at the Slippery Rock Watershed Coalition Symposium, December 4, 2008.
  • Burns, Cory.  Changes in freshwater stream quality due to the deforestation of the Eastern hemlock (Tsuga canadensis) forests, caused by the hemlock woolly adelgid (Adelges tsugae). Biology Capstone project, spring, 2007 through fall 2007.
  • Grieneisen, Becky.  Determination of appropriate rates of Garlon application for control of giant hogweed, Heracleum mantegazzianum.  Biology Capstone project, spring, 2007 through fall, 2007.
  • Zatchok, Jake.  Analysis of Lepomis macrochirus behavior in response to visual and odor cues of predators.  Biology Capstone project, spring, 2007 through fall, 2007.
  • Lambie, B.A.  Bioaccumulation of methylmercury in an aquatic ecosystem.  Environmental Science Capstone project, fall, 2006. 
  • Kawana, Teal.  A study of achromatic recognition and associative learning in the parasitoid Nasonia vitripennis. Biology Capstone project, spring through fall, 2006.
  • Leech, Adam.  Study of Nasonia vitripennis host selection and the relationship between host size, sex ratio and offspring size.  Biology Capstone project, spring through fall, 2006.
  • Montgomery, Jason. Effect of cow, horse, and pig feces on Nasonia vitripenis offspring production numbers in Sarcophaga bullata larvae.  Biology Capstone project, spring through fall, 2006.
  • Barnes, Ryan.  Genetic variability in bluegill sunfish, Lepomis macrochirus, populations in two western Pennsylvania reservoirs.  Van Vranken Research Program, Summer, 2006.  Biology Independent study, Summer 2007.
  • Jurczenko, Chelsea.  Identification of a conserved genetic sequence implicated in hip dysplasia in Canis familiaris with the use of microsatellite markers.  Biology Honors project.  Spring, 2005 to present. 
  • Jurczenko, Chelsea.  Comparison of genetic diversity in bluegill populations in isolated lakes.  Van Vranken Research Program, Summer, 2005. 
  • Reid, Felicie.  Effect of chlorine on population growth of Selenastrum capricornutum.  Environmental Science Independent Study, Spring, 2004.  Presented at the 7th Annual Undergraduate Research Symposium in the Chemical and Biological Sciences, University of Maryland, Baltimore County.
  • Reid, Felicie.  Toxicity of triclosan (2,4,4'-Trichloro-2'-hydroxydiphenyl ether) in fathead minnows and Daphnia.  Van Vranken Research Program, Summer, 2003. 
  • Quallich, Ryan.  Occurrence and concentration of atrazine in the Shanango watershed, western Pennsylvania.  Van Vranken Research Program, Summer, 2002.
  • Shephard, Chaleen.  Mentum deformities of aquatic larval chironomids (Diptera: Chironomidae) exposed to heavy metals.  Fall, 1998.

View Chaleen's Honors defense on chironomid deformities and heavy metals 

  • Bochkoris, Matt.  Genetic differentiation of populations of the goldenrod gall-fly, Eurosta solidaginis. Molecular Biology Honors Project.  Spring, 1998.
  • Hluhan, Denise. The effect of nutrient loading on the diversity and productivity of a freshwater lake. Biology Independent Research project. Spring, 1996 through Summer, 1996.
  • Rhoton, Steve. The effect of varying pH on the symbiotic relationship between Rhizobium and its host plants; bacterial activity and host plant condition. Environmental Science Honors project. Spring, 1995 through Spring, 1996.

View Steve's Honors defense on the effect of differing soil pH on the mutualistic relationship between legumes and Rhizobium

  • Summerville, Keith. Toxicological analysis of atrazine absorption in goldfish and atrazine decomposition in water. Environmental Science Independent Research project. Fall, 1994.
  • Boos, Rob. The effect of varying levels of phosphate, nitrate, and chloride on survival and development of bullfrog tadpoles. Environmental Science Independent Research project. Spring through Summer, 1994.
  • Keller, Sharon. The effect of varying levels of acidity on the development of eggs of the African clawed tree frog, Xenopus laevis. Environmental Science Independent Research project. Spring, 1994.
  • Lary, Monique. Predation, aposemitism, and herbivory: a study of the three-level interaction between milkweeds, milkweed beetles, and frogs. Biology Honors project. Spring through Fall, 1994.
  • Presloid, John. A descriptive study of the vegetation, water quality, and hydrogeologic status of Mercer Bog, Mercer Country, Pennsylvania. Environmental Science Independent Research project. Spring, 1993.
  • DeFillip, Christina. An analysis of the effect of different temperatures and substrate composition on the efficacy of oil-degrading bacteria. Environmental Science Independent Research project. Spring, 1993.
  • Feith, David. Spectrophotometric analysis of the differential absorption of mercury into various tissues of fish. Environmental Science Independent Research project. Spring, 1993.
  • Bouch, Heather. An analysis of seasonal changes in water quality characteristics of a natural lake and a lake in a recently strip-mined area. Environmental Science Independent Research project. Summer, 1991 through Spring, 1992.
  • Hively, Lori. A comparison of the health status of Amish and non-Amish populations in Lawrence Country, Pennsylvania. Biology Honors project. Fall, 1991 through Spring, 1992.


     Web images workshop, May, 2010