'Deep Green' project tracing all plants' roots
By Steve Hatch, Globe Staff, 5/28/2000
Sooner or later, most gardeners start using the scientific names of plants, those unpronounceable, unspellable, unrememberable Latin names. They are precise - there are several things we might call black-eyed Susans, but only one Rudbeckia hirta - and they are universal, used in Weston Nurseries in Hopkinton, the Royal Botanic Gardens at Kew in England and my garden in Marshfield.
The problem is, they change. Sweet autumn clematis has gone from Clematis paniculata to C. maximowicziana to C. terniflora. Members of the genus chrysanthemum were split among several other genuses.
And much more change may be on the horizon.
That's one possible outcome of Deep Green, a ''big science'' effort to trace the phylogeny, or evolutionary development, of all 500,000 known species of green plants on the planet. Formally, the Green Plant Phylogeny Research Coordination Group, this enormous, five-year project was funded by the US Department of Energy, National Science Foundation and Department of Agriculture and involved more than 200 investigators from at least 12 countries.
Deep Green issued its report last summer at the International Botanical Congress in St. Louis. It was a blockbuster.
For example, all green plants evolved from a fresh-water plant, an ''Eve plant.'' The nearest living relatives to the ''Eve plant'' are not waterlilies or magnolias but amborella, a small genus confined to the island of New Caledonia. (It has creamy flowers, red fruit, and I want one.) And of the two great groups of plants, monocots and dicots, the monocots (the grasses and their ilk) do share a single ancestor, but the dicots do not, which means they are not a natural grouping.
None of this will affect us gardeners, but the next might: Deep Green has resulted in calls for conventions to reflect cladistics, which is another name for classification, based on the phylogenetic relationships and evolutionary history of groups of organisms.
That is big, huge.
According to Brent Mishler, one of the principal investigators of Deep Green, names should reflect reality, so ''even though it's inconvenient to have a name change, it's better to have names that bring them together.'' Besides, he said, at least half of the Linnaean classifications are wrong.
Mishler, director of the herbaria at the University of California at Berkeley, wants to get rid of the system of taxonomic ranks - kingdom, phylum, class, order, family, genus and species - that he calls a holdover from an 18th-century creationistic world view.
The way things work now, taxonomists group or rank plants, then nomenclaturists name them based on those rankings.
The current system groups species by the number and arrangement of their reproductive organs, the stamens and pistils, among other things. Because it is arbitrary, revisions happen, and plants get booted from one genus to another. Plant names also are based on who first published their descriptions, and so plant historians can get a name changed on that basis. Attempts to freeze names to present usage have failed.
Under a cladistic naming convention, a plant would not be in a group. Its full scientific name would be based on its evolution, would in a sense be its family tree. According to Mishler, corn's name might be: Mays Zea Gramineae Monocots Angiosperms Eukaryota Life. Humans would be: Sapiens Homo Homidae Primate Mammalia Vertabrata Metazoa Eukaryota Life. Each component of this name represents an evolutionary branching, not arbitrary groupings like class and family. Any later adjustments would simply involve sticking one piece of the naming code inside the new one.
The value of cladistics lies not only in pure science but in knowing the true relationships of plants ''and using that to make predictions for genes that are potentially useful to biotechnology and medicine,'' Mishler told me in a recent telephone interview. ''Even though it's inconvenient, it's actually important for predicting things like resistance to pests. It's very predictive. It's the single most predictive thing about unknown properties.''
Most new drugs come from natural products, Mishler noted. And knowing what plants are closely related to crop plants might allow plant breeders to transfer desirable traits from wild relatives to domestic species. ''So there's a whole host of really cutting-edge things that may come from this,'' he said.
Deep Green's first five-year grant has expired, but new applications are pending and a second round of investigation is expected. Mishler said the project still is concentrating on compiling the clades, collections of branches with single common ancestors, and will turn to nomenclature later.
But discussions have begun nonetheless, and they are vigorous. The proposal has been called everything from ''the greatest thing since sliced bread'' to ''moronic,'' and this by usually reserved academics. The range of predictions is also wide, from a new convention being a dead certainty to it will never happen. The worst thought may be that both systems will happen, resulting in a confusing mishmash of names, or perhaps it will all work out nicely, with cladistic naming evolving into the finally surviving system. (My guess is that any new system will retain the binomial species names, simply to keep the peace.)
''I know full well that there is resistance ... to name changes,'' Mishler said. ''I'd really like to convince the users of plant names.''
Cladistics on the broad scale of Deep Green was possible only in the last 15 years, with the development of DNA analysis and the availability of computers to analyze that data. The present system of taxonomy did pretty well based on superficial observation, but getting down to chromosomes establishes real identities.
Ultimately, this kind of research may lead to harmonization of nomenclature systems (botany, zoology, bacteria) into a general ''biocode'' for all biological sciences. There are now thought to be five kingdoms: red algae, green plants, animals, fungi, and stramenopiles, which look like plants but do not photosynthesize. These embrace the 1.4 million organisms identified so far, with an additional 10 million or more remaining to be identified.
As with human royalty, these kingdoms are related. Among plants, it is believed that the chloroplasts inside the plant cells are more closely related to each other than are the plants themselves. And fungi are more closely related to animals than to plants.
Mishler understands all this better than most. In an interview with the Canadian Broadcasting Corp. last fall, he said: ''If you're eating a salad that has both lettuce and mushrooms on it, you're more closely related to the mushrooms than you are to lettuce. But you are related to both, and I don't mean metaphorically, I mean literally, you're related to both.''
This story ran on page 14 of the Boston Globe's Northwest Weekly on 5/28/2000.
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