A genus that no longer exists, of plants that stop cell division at metaphase

Animals eat plants. Plants seem to generally object in their varied ways. Over the few hundred million years this has been happening, plants have gotten clever about fighting back. The thorns of the rose are one example of the results of this long running battle between the herbs and the herbivores.

Androcymbium is a genus that no longer stands as valid - it is now part of the genus Colchicum. Like many plants and animals that have been grouped together by morphological taxonomists in decades and centuries past, the groupings have proven to be correct in some ways, and grievously in error in other ways. Those errors started becoming visible when people started sequencing the genomes of these organisms. Molecular phylogenetics has reworked hundreds of years of looking at plants and comparing their features to understand how they are related to each other. Sometimes this has upended what had appeared to be well understood groups.

 

Androcymbium ciliolatum has a new name, Colchicum capense subsp. ciliolatum. My plants came from a Garden Club meeting at the Los Angeles County Arboretum in 1986. I've grown them ever since. This is the first year I've convinced these natives of Namaqualand, South Africa to flower.

This plant has flowers that are actually not the flowers (the same is true of Poinsettia, where the colored "petals" are actually specialized leaves called bracts in some cases. The true flowers hide in the center of these white-green desert chalices.

There is a single flower hiding down in there, with six petaloid filaments ringing the three carpels and styles.

What does this have to do with defenses? 

Androcymbium are poisonous plants if ingested. Their toxin, Colchicine, is a strange one, as it is used in taking photographs of chromosomes. Colchicine is an alkaloid that stops cell division at metaphase. That is the part of cell division where all the chromosomes are lined up in pairs preparing to separate to two new cells. 

Careful use of Colchicine on the growing tips of plants can cause a kind of error in copying the chromosomes. They fail to separate. Then the cell proceeds to go on to more ordinary affairs as if it had divided. The cell now has twice the number of chromosomes that it had prior to its encounter with colchicine. This is how tetraploid plants are made from diploids. Tetraploids are often larger and more vigorous than the diploid plants that they once were.

This same treatment does not work with animals. In animals, the chromosomes line up and do not separate, but the cells do not restart the cycle normally. Often, they die. Sometimes they wait until the colchicine clears the system, then try the cell division again. Generally the more complex the animal, the worse the effects of colchicine. Hence large herbivores that survive taste testing the plant often avoid it for the rest of their lives. Hence the plants are left a bit more alone to grow and reproduce.

This species is native to Namaqualand, an amazing and wonderous part of South Africa - a subtropical humid desert. The same place the "living stones" of the genus Lithops are found. There is little vegetation, and lots of animals looking for a meal. Few bother the Androcymbiums.