MAKE IT GREEN: How we name plants has changed over the past 50 years

Readers: This is part two of a three-part series about naming plants. I hope you find the story of plant naming as interesting as I do.

Imagine for a moment that you are looking at every kind of living creature on earth. Plants. Fungus. Fish. Bears. Bacteria. Everything. Nobody really knows how many species are currently living on Earth. Some estimate more than 2 million unique organisms populate our planet.

Now, imagine your view stretches back through time, through billions of years, and you are seeing every critter that ever lived, through all of time, countless hundreds of millions of species. Every organism, extinct or not, that ever lived. Every organism that lived and died, each worthy of our respect, and awe.

How do we make sense of this? How do we even give them all names?

Among the plants, nobody establishes the historical picture of naming better than Anna Pavord in her book “The Naming of Plants,” a languid and loving consideration of our relationship with plants through recorded history. Pavord chronicles the earliest plant names, properly credit important work by Arabian scientists, and tells how naming of organisms came to be called taxonomy, which is more properly a specialization of Systemics, which considers variation and relationship of organisms more broadly. It was Pavord’s book that piqued my interest in the topic.

Both of these fields have undergone a bit of a revolution in the past 50 years or so, as taxonomists have discovered computers and have the assistance of DNA to piece out plant relationships.

It’s complicated!

Many of us learned the “Five Kingdom” approach to organizing life: Bacteria, eukaryotes, fungus, plants, and animals. This approach is based on largely body plan, and doesn’t account (much) for evolutionary ancestry. It does, though, lead to the familiar — and still useful — organizational tree remembered by anyone with high school biology: Kingdom, phylum, class, order, family, genus, species.

This grouping process is simple: our first group separates the plants, the animals, and the bacteria. Among the plants, for example, we can further separate those with flowers, and those without flowers. Among the flowering plants, there are those with veins in a straight line, and there are those with articulated veins.

Each point of departure identifies a smaller group that is more similar than previous. Soon, we are talking about the rose family, or the grass family; and then we are talking about the ficus genus, and finally Ficus benjamina, and F. pumila, and F. rubiginosa, and so on.

In the end, each plant not only has a unique name, but is also part of a much bigger picture. Sweet. But is it useful?

Seeing the big picture

Along comes a German entomologist named Willi Hennig in the early 1950s with an approach called Cladistics which has taken the systemics field by storm. Cladistics depends on a powerful idea: that members of a group share a common evolutionary history. Put another way, plants are said to be closely related depending on the proportion of characteristics they share with each other. More important is this: the more they share common characteristics, the more recently they diverged from a common ancestor.

Cladistics defines something called “primitive characters.” These are attributes shared by all members of a group. Mammals, for example, have four legs; all mammals inherited this characteristic from some animal in the olden days, possibly from a reptile or similar creature.

Why is this important? For one thing, cladistics allows scientists to reach back over those billions of years. They can create a lineage of organisms that evolved this way or that into the modern creature.

This single notion ties together the entire natural history of our planet into a coherent image. Living creatures today are only a very small part of earth’s natural history, but cladistics attempts to tell us exactly which part is played by each organism, extant or extinct.

Sure, there are problems with cladistics. Determining which characteristics are considered when comparing, and how to weight them, can be a subjective process. A bigger issue, perhaps, is the incomplete fossil record. Among botanists, inter-specific hybridization is a tough issue for the method.

In the next installment, I’ll look at these issues, and at how Carl Linnaeus attached his name to thousands of plants.

A reminder from your Design Pundit: summer sessions at Barron Collier AdultEd begin the week of June 6. Get the latest information on the web site below.

Michael Spencer is a landscape architect who has been in business nearly 26 years. Visit his website, www.msadesign.com. Email: ms@msadesign.

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