Monday, July 1, 2013

Botany Rules 4: Who Makes the Rules?

Nasturtium officinale
Nasturtium officinale
NOT Nasturtium nasturtium-aquaticum
     Why is it Nasturtium officinale not Nasturtium nasturtium-aquaticum as some other botanist proposed?

    Who makes the rules for plant names?

   The answer is: The International Association of Plant Taxonomists (IAPT) (home page).

Tropaeolum, Tropaeolaceae
Tropaeolum, determined to be
sufficiently different from
other plants that it is the
only genus in family Tropaeolaceae
   The rules for naming plants and for how they are organized into groups are agreed upon by vote of the International Association of Plant Taxonomists. They meet at International Botanical Congresses, about every 6 years. Suggestions and amendments come out of committees, are voted on by mail and then ratified by the membership attending the International Congress. In this way, the rules of plant naming evolve. Current rules:  

     Like all of science, it is a human activity. Like all human activities, therefore, it is subject to quirky human behavior. 

    Good ideas for coherence in plant naming always run into resistance based upon tradition. This leads to politics and, when things go well, to happy compromises. Compromises are sensible and in human endeavors, necessary. But years later, when I explain the rules to someone new to the system, the compromise can seem pretty weird.

    (Disclosure: I am a plant ecologist not a plant taxonomist. I am a user of plant names, not a maker of orderly plant names. I confess I sometimes find the debates of taxonomists puzzling or amusing.)

      There are well over 400 families of plants subject to the IAPT's naming rules. A coherent system for the names of families was obviously going to be very helpful. So a system was proposed: each family was to be named by adding -ceae to a genus in the family. Thus. the rose family, Rosaceae, is named for the genus Rosa and the Ulmaceae for Ulmus, elms. 
Rosa Rosaceae
a rose, genus Rosa, rose family, Rosaceae
     However there were several big families with traditional names. People did not want to change familiar names. The debate at the International Botanical Congress was resolved by a compromise. All families received a name based on one of the genera in the family, but a few families could retain their traditional name. For them, both names were accepted. 

    The families with two names are: 
the carrot family, Apiaceae, traditionally called the Umbelliferae; 
the palms, Arecaceae, traditionally Palmae;
the sunflower family, Asteraceae, traditionally called the Compositae; 
the mustards, Brassicaceae, traditionally Cruciferae; 
the clusia family, Clusiaceae, traditionally Guttiferae; 
the grass family, Poaceae, traditionally called Gramineae; 
the pea famly, Fabaceae, traditionally Leguminosae, and
the mint family, Lamiaceae, traditionally called Labiatae.

To read the formal language on families go to: International Code of Nomenclature for algae, fungi, and plants Sect. 18 This agreement was reaffirmed by the Eighteenth International Botanical Congress in Melbourne, Australia, July 2011, called the Melbourne Code. 
palms, Arecaceae, palm family
palms, Palmae, palm family

palms, Palmae, palm family
palms, Arecaeae, palm family



     For these families, both family names are correct, use the one you prefer.

      People learning the plant families for the first time find the system odd, since they can comfortably learn Arecaceae and Brassicaceae and most of them have no stake in the old names. 

    In defense of the old names, I should note that they tend to be descriptive: Umbelliferae describes the shape of the flowers in the family (umbels), Palmae is obviously descriptive compared to Arecaceae, Compositae refers to the compound (composite) flowers in the family, Cruciferae the cross-shaped (4-petal) flowers of mustards, etc. 

     Functionally, this ongoing compromise means that in an alphabetized list of plant families, if you can’t find the carrot or dill in the A’s (Apiaceae), look under U (Umbelliferae), and if the sunflowers aren’t under A, check C (Compositae). 

     It also makes it just a bit harder to recognize a family name. If it is capitalized and ends in -ceae, then it is the name of a plant family. But the older family names end in -ae. I do not think there are genera or species that end in ae, so -ae or -eae clues you to the fact it is a higher category, in fact, a family, but it is not as clear as seeing -ceae.

     <to be continued in next post: Botany Rules 5: New Rules and Ongoing Discussion >

Kathy Keeler, A Wandering Botanist

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