Piecing together the tree of life

Summer is ending, and I’ve migrated back to Copenhagen for the rest of the year.

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Being an ecologist, one of the first places I went to visit was the botanical garden and the university’s geological museum. I stumbled upon an exhibit of the Flora Danica – a guide to all the plants of Denmark, published under royal authority in 1761. The flora consists of thousands of engravings, each drawn carefully to help the reader identify the species from flowers, leaves, stems, and root. Color prints made from the engravings were distributed freely to bishops around the country, with other editions’ prices subsidized by the crown. It is a beautiful piece of work, but what struck me most was its complete lack of organization. Today, we have a robust system for organizing species, which we depend on heavily for a range of science and conservation applications. To me, seeing a book of plants without an organization scheme is like imaging a dictionary that isn’t published in alphabetical order. To understand why, we have to go back in time.

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In the 1700s, taxonomy (the study of classification of organisms) was a new subject. Linnaeus published his famous Systema Naturae in 1735, but his ideas were by no means well-accepted immediately, nor was his approach based on arguments deeper than morphological similarity. As a result the Flora Danica, published a few decades later, was produced as an arbitrarily ordered set of color plates. Each publisher or book-binder could arrange these plates however they pleased. While charming, that system made it difficult to generalize and think more scientifically about plants. In fact, it was unclear that there should even be a correct way to organize species (why not group by poisonous and not-poisonous, for example) until the advent of evolutionary biology. Darwin showed that species arise from other species, providing a natural organization – more related species in the same groups, because they share the same evolutionary history. Gnetum, for example, looks passingly similar to Apocynum, but the groups are actually separated by tens of millions of years of evolution.

Modern cladistics, under Hennig, pushed the evolutionary idea forward and gave us the basis for our modern groupings of species.Below, you can see a small part of the botanist Alwyn Gentry’s monumental work, A Field Guide to the Families and Genera of Woody Plants of North west South America, giving the characters that help to separate different evolutionary groups of plants.

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Illustrations have also changed – the lush detail of the Flora Danica is replaced by sparse line drawings, equally informative, but perhaps missing some indefinable romanticism of the earlier work.

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Modern cladistics and molecular biology work – DNA sequencing, for example – have almost made it possible to know the full plant tree of life. You can see an evolutionary tree from one of the more recent studies (from 2010) below.

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I think that in the next few decades the work of classifying all the plants of the world – and perhaps, all the known species – will be largely complete. We are riding a wave of advances in computer power and DNA sequencing methods that will build us a complete tree of life. Such a thing – a catalog and moreover an index to all the species that live – would surely be inconceivable to the royal botanists compiling a flora all those centuries ago.

5 Comments Add yours

  1. brubaek says:

    Hi Benjamin. A really nice piece on Flora Danica and cladistics. I have followed your blog for a while, and was trilled to see that our exhibition Flora Danica inspired you to write.
    I have been meaning to tell you, for a while now, that I think your a brilliant communicator. You manage to take experiences from your daily work and put them into a larger context, in a apparently seamless way. Working with exhibitions, I know how difficult it is to make complex knowledge available, in a way that the rest of us can understand it. I think your blog is managing just that.

    All the best,
    Birgitte Rubæk, Exhibition Designer,
    Natural History Museum of Denmark

    1. bblonder says:

      Thanks, Birgitte. The Flora Danica exhibit is beautiful – I only wished there was an opportunity to look at more of the plates, or actually handle the original engravings. Were you part of the design team? I hope we will run into each other soon now that CMEC is part of SNM.

      1. brubaek says:

        Thank You! I was the project manager at two Flora Danica exhibitions. *Remember there is an extra exhibition Flora Danica Zoom, in the botanical garden. But that one closes end august!
        If you want you can see the real FD live at the Botanical library. Henning Knudsen is a treasure of knowledge on the subject and very generous. Give me a call if you deside to go there at some point, it would be nice to meet you.

      2. bblonder says:

        Thanks! I’m traveling for a conference now but would love to see the original once I’m back.

        Ben

  2. monomiao says:

    This reminds me of the feeling when I visited the National Postal Museum in DC and saw the history of mail box. There were no mail boxes at the beginning when people started using mails. I also had this kind of feeling when someone told me the story that the speed on highway wasn’t limited initially. It is interesting to think back about the histories of these things that we take their existence for granted toady.

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