Oh the Diversity of Dorstenia

When I first encountered a member of this genus, I was given ample opportunity to decipher the family to which it belongs. Try as I might, I simply could not conjure up enough of a search image to place it. To add to the matter, I was only seeing a single representative. The most troubling feature were the strange structures that stuck out above the leaves. What could they possibly be? My first guess was a spent flower but my hand lens revealed that the little pock marks covering the shallow bowl-like structure were in fact flowers. What on earth was this plant?!

It was soon revealed that this was a member of the fig/mulberry family Moraceae. The plant in question hails from the genus Dorstenia. As it turns out, this is quite possibly the most peculiar genus within the family. The Dorstenia are a rather widely distributed grouping of plants that exhibit an even wider variety of growth forms. Whereas most of the Moraceae are woody trees, Dorstenia is largely dominated by both herbaceous and succulent forbs as well as semi-woody or "suffrutescent" forms. 

The reproductive structures are strange. They are reminiscent of a fig that has been turned inside out. The shallow bowl is covered in tiny flowers. Fruits ripen within the tissue and then explode when ripe, catapulting their seeds. 

Aside from their appearance, Dorstenia also exhibit an interesting distribution. They are found in both the Old and New World tropics. A lot of work is being done to elucidate exactly where this genus evolved and how it radiated outward to its current distribution. Molecular evidence suggests that Dorstenia arose in the Old World tropics and gradually radiated outward across land bridges. A possible explanation for their presence in the Americas could be that they crossed the ancient land bridge between Asia and North America and radiated out from there. As climates began to cool, Dorstenia in North America would have gradually been reduced to all but those living in Central and South America. Without fossils, no one can say for sure. 

Regardless of where they came from and how they got there, Dorstenia are interesting plants. Their peculiar appearance has earned them a following in the more exotic gardening corners. They are certainly a conversation piece. 

Photo Credits: Cerlin Ng (http://bit.ly/1WMzwg5) and 22Kartika (Wikimedia Commons)

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