Field & Street | Field & Street | Chicago Reader

News & Politics » Field & Street

Field & Street

by

comment

Illinois' last wild population of the lakeside daisy was accidentally buried under a slag heap at Commonwealth Edison's Joliet generating station in 1981. Even without Com Ed's massive intervention, the plant was almost certainly headed for extinction. Only about 30 plants remained alive at the end and they had not produced any seed since monitoring began in 1970.

Fortunately, a man named John Kolar was able to pull three plants from the wreckage. He planted them in his backyard where they thrived and even reproduced by vegetative means. But despite the presence of bumblebees and other pollinators during the plant's flowering season, the daisies remained barren. They produced no seeds. The time seemed right for removing them from the endangered list in Illinois and officially declaring them extirpated.

The move might have been made if the problem of the lakeside daisy hadn't drawn the attention of Marcella DeMauro, a graduate student in biology at the University of Illinois at Chicago. DeMauro was looking for a thesis project at the time, a project that would be both good science and a contribution to conservation. The lakeside daisy seemed just the thing.

The lakeside daisy, like our familiar oxeye daisy, is a member of the Compositae, the huge family of flowering plants that also includes sunflowers, black-eyed Susans, asters, and thousands of others. Composites get their names from the structure of their flowers. What looks like a single flower is actually a whole cluster of flowers, a dense central group of disk flowers--the black "eyes" of a black-eyed Susan--and a surrounding ring of petallike ray flowers. Both disk and rays of the lakeside daisy are a bright yellow.

Lakeside daisies belong to a genus, Hymenoxys, whose center of abundance is in the west, particularly the dry, shortgrass prairies of the Great Plains. The species ranges from Texas to British Columbia, but the plants in our region belong to a distinct variety, Hymenoxys acaulis glabra, which grows only near the Great Lakes.

It is likely that this plant invaded the east during a period of unusually dry, warm climate four to six thousand years ago. It survived through the cooler, wetter periods that followed by occupying an unusual habitat called a dolomite prairie.

Dolomite is a form of limestone that is very rich in magnesium. The dolomite around the Great Lakes dates from about 400 million years ago and was laid down on and around coral reefs in the seas of the time. It is hard rock that tends to form uplands. The most prominent midwestern dolomite is the Niagara escarpment, a narrow, arcing band of rock that extends from Milwaukee all the way to Rochester, New York. The route is north through the Door Peninsula--where it forms the cliffs in Door County--east along the southern edge of upper Michigan, and then southeast through a chain of islands in Lake Huron and the Bruce Peninsula in Ontario to Niagara Falls. Another band of dolomite extends from the western end of Lake Erie to northeastern Illinois.

Dolomite prairies grow where the bedrock is at, or very near, the surface--where the shallow soil dries out quickly after rains. The dominant plants of the dolomite prairie are mainly species more typical of western grasslands than of the lush, black-soil prairies of Illinois.

There were several dolomite prairies on the floodplain of the lower Des Plaines River. Few remain now, but two--the Lockport Prairie and the Romeoville Prairie--have survived long enough to be set aside as Illinois nature preserves. The last Illinois lakeside daisies, the ones Com Ed buried, were a few miles downstream from Lockport.

The only other known populations, of the Great Lakes variety of the lakeside daisy are on Manitoulin Island on the Canadian side of Lake Huron--part of the Niagara Escarpment--and on the Sandusky Peninsula on the southwestern shore of Lake Erie in Ohio. The Ohio plants, several thousand of them, all live in an old dolomite quarry. Both of these populations set seed and reproduce normally.

The first step in Marcy DeMauro's project was to transplant four of John Kolar's plants to the university's greenhouse, where she could find out why they weren't setting seed. Her work confirmed her initial suspicion that the problem was, in her words, "an obligate outcrossing breeding system that is enforced by a genetically controlled, sporophytic incompatibility system."

An incompatibility system is a sort of botanical incest taboo that prevents plants from fertilizing themselves or from fertilizing close relatives. Normally, sexual reproduction in plants involves a pollen grain landing on the tip of the pistil of a flower. The grain germinates, and a pollen tube grows into the pistil until it reaches the ovule. Sperm moves through the tube to fertilize an egg. In plants with incompatibility systems, the pistil, in effect, reads the relevant portion of the pollen's genetic code and blocks the growth of the pollen tube if the genes are too similar to its own. In other words, the Illinois lakeside daisies were not reproducing because all the remaining plants were close relatives. Perhaps they all had the same mother.

The next step in DeMauro's project was to get permission from the Ohio Department of Natural Resources to collect some plants from their one population. Once she had that, she brought back 20 Ohio plants and began crossing them with her Illinois specimens. They produced seed like crazy, but what could she do with it?

Some exploration turned up six possible sites for wild lakeside daisies along the lower Des Plaines, four on unprotected land plus the two Illinois nature preserves. There was one other possible site, the Manitou Nature Preserve along the Illinois River in Tazewell County. This is a gravel hill prairie, where the gravelly soil and the elevation of the land combine to produce dry conditions like those on the dolomite prairies. Lakeside daisies grew there in the 30s, but had disappeared by the early 60s.

Early this spring, she submitted a proposal to the Illinois Nature Preserves Commission outlining a plan to transplant lakeside daisies to the Romeoville and Lockport prairies. She had germinated the plants in the greenhouse last November and had kept them growing though the winter under sodium-vapor lights. She chose the two sites not only because they are protected, but also because they are in Will County. She now works as a natural resources manager for the Will County Forest Preserve District, which manages the preserves for the state.

The commission is bound to look on a proposal like this with some suspicion. Our nature preserves are not outdoor greenhouses for endangered species. They are supposed to be the most pristine, undisturbed examples of native plant communities remaining in the state. The commission's job is to keep those communities healthy. Introducing new species, even species that we believe ought to be a part of these communities, always carries some risk. What if the new species become serious competitors with established plants?

DeMauro's response to this question was to point out that neither of her sites was entirely pristine. At Lockport, for example, the low wet areas are very high quality marsh and sedge meadow, but the higher ground had been heavily grazed, and the highest ground is actually the remains of an old haul road built to carry dolomite from a quarry at one end of the preserve. Her lakeside daisies--which favor the highest and driest land--would be introduced into disturbed ground, successional communities, weedy places in the process of changing back into healthy, stable, climax communities. The daisies would be competing with weeds like European buckthorn and meadow parsnip rather than with native plants.

On May 10, the commission voted four to three to approve the project, and DeMauro went to work. Using forest preserve staff augmented by volunteers, she set out 600 plants. On May 24, she led me through both sites to check on the progress of the plants.

The lakeside daisy has a growth form rather like a dandelion. The leaves are all clustered in a rosette, at the base of the plant. The leafless flowering stalk grows out of the center of the rosette. On the newly planted seedlings, the rosettes are only an inch or two across. Plastic popsicle sticks mark the places where they were planted, and without them, we couldn't have found very many. The sticks are all numbered and color coded so that the success of the various genetic strains can be monitored.

The soil at Lockport Prairie is no more than six inches deep at most, and in many places, the bedrock is right at the surface. Lakeside daisies love this sort of situation, and many of the plants were placed in cracks between slabs of exposed rock. Tiny cairns surrounded the seedlings, providing some support and protection for them. When the roots are better established, DeMauro will remove these cairns.

So far, the plants seem to be doing well. We saw only one obviously dead specimen. The rest looked green and healthy, and one precocious individual had already grown a bright yellow flower. Lakeside daisies bloom in April and May--they are the first flower of spring on a dolomite prairie--and these plants could carpet the ground with bright yellow as early as next spring.

The real question is how long they can survive. Twenty different family lines, each with a different maternal parent, are represented on the prairies now. The random loss of genes through the actions of chance could reduce that number. Natural selection could reduce it further if some of the lines are not well adapted to their new situation. DeMauro's work may in the end only delay the loss of the lakeside daisy.

To ensure the long-term survival of our wild plants and animals, we need preserves big enough to support large populations with gene pools big enough to overcome the normal losses of life in the wild. "Diversity comes with numbers," DeMauro told me, and diversity is what keeps nature alive.

Add a comment