Biology at Williams

Faculty and Staff

Joan Edwards
Joan Edwards
Joan Edwards
Washington Gladden 1859 Professor of Biology at Williams since 1979

Office: 217 TBL
Phone: (413) 597-2472
Area of Interest: Ecology

Courses taught recently
Recent Honors Students* and Research Assistants
Isle Roayle Research Team
Isle Royale Research Team 2005 on the MV Ranger III returning from Isle Royale July 2005.
Top Row: Clara Hard, Prof. David Smith, Ellen Crocker
Front Row: Meredith Gansner, Prof. Joan Edwards, Lisetta Shaw

Ellen and Whitaker filming
Ellen Crocker and Prof. Dwight Whitaker (Physics Department) filming exploding Impatiens fruits using the ultra high-speed video camera. Williamstown, July 2005
Chris Eaton
Chris Eaton ‘05 examining Potentilla fruticosa for Empria larvae.
Isle Royale, July 2004.
Nancy and Cathy looking at Impatiens
Nancy Piatczyc, Electron Microscopy Technician, and Cathy Small ’09 looking at Impatiens pallida pollen with short raphides on the SEM.
Pollen grains of Impatiens
Pollen grains of Impatiens pallida
with raphide (calcium oxalate) needles.

Lilium philadephicum
(Wood Lily)
Lonicera canadensis
(Fly-Bush Honeysuckle)
Cornus Canadensis (Bunchberry) visited by Evodinus monticola
(a long-horn beetle)
Empria obscurata (Early Strawberry Slug) larvae eating the petals of Potentilla fruticosa (Shrubby Cinquefoil)


My main research focuses on the evolution of plant-animal interactions—flower-pollinator associations and plant-herbivore interactions. I am particularly interested in how plant behaviors enhance reproductive success. Flower-pollinator studies include the evolution of exploding flowers— e.g., explosive flowering in bunchberry (Cornus canadensis) and stinging nettles (Urtica spp.), and other flower behaviors—e.g., studies on pollen protection in wood lilies (Lilium philadelphicum) (see PDF) and in jewelweed or touch-me-not (Impatiens spp.), and patterns of flower longevity in boreal plants. My plant-herbivore studies include sawfly (Empria obscurata) herbivory on shrubby cinquefoil (Potentilla fruticosa) and other plants in the rose family (Rosaceae) and moose-plant interactions.

I also have two long-term studies of plant population dynamics. Both studies have permanently marked quadrats, which are checked annually. The first are rocky shoreline plants at the northeastern end of Isle Royale National Park. The second are populations of the invasive plant, garlic mustard (Alliaria petiolata), in temperate deciduous forest of Hopkins Memorial Forest.

Each project is described briefly below.

Exploding Flowers
The 1st millisecond of a Cornus canadensis bloom. Each frame is 0.1ms. The blur in each fram shows the distance moved in each 1/10th of a millisecond!

Exploding Flowers and Ultra-fast Plant Movements

One typically thinks of plants as sedentary and slow moving, but the most rapid movements in animals rely on stored mechanical energy (not muscle power!), thus plants should be able to match or surpass the fastest plant movement. Using ultra high-speed video (10,000fps) we measured the speed of rapid movements in plants. Our web site on the exploding dogwood flowers gives more details. We are also studying other rapid plant movements from the explosion of Impatiens fruits to the air-gun propulsion of spores in Sphagnum. And we worked with Dr. Dave Kelly at the University of Christchurch, New Zealand on exploding Mistletoes (PDF of paper and link to Dave’s web site).

Reversible Cryptic Coloration in the sawfly, Empria obscurata (Early Strawberry Slug) (Hymenoptera)

Many animals use cryptic coloration to avoid predators. Most have fixed colors to match one background. A few can some alter their color to match different background. We discovered that the larvae of Empria obscurata are translucent, taking on the color of their food. We are studying the adaptive significance of this extraordinary trait.

Pollination Biology and Seed Dispsersal in Impatiens

Rhingia nasica (Syrphidae, Diptera) on Impatiens pallida (Balsaminiferae) flowers. Rhingia collects both pollen from the anthers and nectar from the spur on the sepal (see below), but is a “robber” as it does not make the correct contacts to effect pollination.

Floral Behavior of Boreal Forest Plants

Moose-Plant Interactions

I studied moose-plant interactions at Isle Royale National Park where I observed moose feeding behavior (300+ hours of observing moose and recording their diet in terms of the number of bites of each plant species) and studied their impact on plants. See papers on Aralia nudicaulis (2 pdf’s) and moose behavior (3pdf’s).

Long-term Population Dynamics of Great Lakes-Arctic disjuncts. Isle Royale National Park, Lake Superior, Michigan.

The rocky shoreline at the Northeastern end of Isle Royale National Park harbors relict populations of arctic plants. Often the next closest population is in the arctic. Since 1999 we have mapped and kept track of individual plants on three different islands and seven different sites.

Long-term Population Dynamics of the invasive Eurasian Plant, Garlic Mustard (Alliaria petiolata, Brassicaceae). Hopkins Memorial Forest, Williamstown, Massachusetts.

We designed permquads (stainless steel quadrats) that are 0.5 x 0.5 meters on a side and are anchored to the ground with u-shaped stainless steel pins). Each year we record the number of rosettes, flowering plants in the quadrat. We also count the number of seeds on each plant and in each seed trap. These data provide information to chart invasion, fluctuations in populations levels, and to project future population sizes.

Selected Publications (*undergraduate co-author)