Tuesday, July 19, 2016

More Crop Mimics

I've previously posted about a form of mimicry in plants (called Vavilovian mimicry) where one [or several] wild species end up mimicking a crop species due to the selection pressures in crop fields. Since then, I've come across a few other species that are useful examples for the topic.

Wheat (top) vs. Darnel (bottom).
[from link]
Darnel (Lolium temulentum) is a  mimic of wheat. It looks almost identical to wheat plants right up until the seed heads form (see at right). The seeds themselves are large and are indistinguishable from those of wheat after threshing. The seeds are also highly poisonous, leading to the common name of "Poison Darnel". When wheat contaminated with sufficient Darnel is milled into flour, the resulting bitter taste reduces its value.

Darnel control efforts have limited success and the plant is found essentially everywhere wheat is grown. Even though the toxic character of this species (when infected) means it will likely never be developed into a primary crop, it is still a nice example of Vavilovian mimicry.

Another common weed in wheat fields is Small Canary Grass (Phalaris minor). It also produces large seeds that would probably get sorted with wheat seeds at the end of the season and its seedlings look very much like those of wheat.

As a general rule, any random grass species is going to be a much better mimic of the grass we call wheat than any other random type of weed would be. Of the five weed mimics of wheat that I've come across (below), all are grasses and three have become major crops in their own right.

Rice crops are often plagued by weedy forms called "Red Rice" due to the red color of their seeds. They are generally less productive than the main cultivated varieties, so farmers try to keep it out of their paddies. Red-Rice happens to be the same species as the cultivated types. It evolved from (or alongside) cultivated rice so it really isn't a case of Vavilovian mimicry, even though it is a useful example in the discussion of crop weed mimics.