Joan Edwards

Research Interests

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.

In Williamstown, I am studying the conservation of fall blooming asters and goldenrods.  These species are an important part of our New England biodiversity heritage.  We are in the center of diversity  for  goldenrods (Solidago spp.).  In New England as forest is replacing field habitat, the number of  asters and goldenrods is declining. These are species are not only important for maintaining floral diversity but they also provide nectar and pollen for pollinators just before they overwinter.  Currently we are studying how mowing practices impact both the flowers and their pollinators.

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.

More on Research

Each research project is described briefly below:

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.

Recent Honors Students* and Research Assistants

• Lauren Buckley ’00*
• Brendan Reid ’02
• Sarah Klionsky ’03*
• Kimberly Kemper ’03*
• Jacqueline Hom ’04
• Ken Brown ’05
• Chris Eaton ’05*
• Ellen Crocker ’06*
• Donald Mitchell ’06
• Clara Hard ’06*
• Alejandro Acosta ’06
• Lauren Moscow ’07
• Sarah Martin ’07
• Catherine Small ’09
• Kimberley Taylor ’08*
• Emily Brown ’08*
• Jacob Blessing ’09*
• Allie Gardner ’10*
• Jessy LeClair ’10*
• Nora Mitchell ’10*
• Jillian Hancock ’11*