Saturday, May 16, 2015

Running Buffalo Clover

According to the Internet, yesterday was Endangered Species Day! I saw a lot of posts about all of the endangered animals worldwide, of which there are a lot of fascinating and adorable creatures. But, I noticed very little attention being paid to the plant kingdom. I felt someone should change this! According to the US Fish & Wildlife Service’s Environmental Conservation Online System, there are over 600 federally recognized endangered plant species in the United States. If you count threatened and endangered, there are a total of 886. Being from the Midwest, I decided to pick a plant that was endangered in my local area to highlight today. Without further delay, may I introduce Trifolium stoloniferum Muhl. ex Eaton, commonly called running buffalo clover. 
Photo by U.S. Fish and Wildlife Service, Sarena Selbo

Running buffalo clover is part of the Fabaceae family, the legumes, which also includes soybean and peas. It used to be wide spread across the Midwest, commonly reported in the trails left by buffalo (hence the common name), deer and elk. At one point, it was considered to be extinct until two populations were discovered in West Virginia in 1985. Since then populations have been rediscovered in Indiana, Ohio, Kentucky, Missouri and Arkansas. 

I’m sure you’ve seen clovers, I know I spent plenty of time as a child combing through a field of clover looking for the supposedly lucky 4 leaf variety. There are over 200 recognized species of clovers, so how does one identify the endangered running buffalo from the more common introduced white clover (Trifolium repens L.)? First, buffalo running clover puts out runners over the soil letting it spread across the plains, hence the running portion of its name. Second, notice in the diagram drawings that the stem of white clovers flower do not have any leaves, while the running buffalo has two paired triple leaves on the flower stem. Third, buffalo running clover lacks the white lines on its leaves that are typically observed in clovers of the genus Trifolium. And last, if you can get up close to the flowers, they have little purple tinges where white clover are all white.
Running Buffalo Clover
White Clover

When I first saw that a clover was endangered in my area, my immediate thought was that it must have been out-competed by any number of the clovers that have been introduced. Native species being squeezed out by introduced species is common in the plant kingdom. But after some reading, it turns out that running buffalo clover was decimated by the loss of bison and other large herbivores from the Midwest. The clover needs the disturbance of herbivory to thrive. The seeds can be spread via passage through the intestinal system. So it would appear that the loss of the major herbivores has led to the decline of this unique clover species. Though development (loss of habitat) and competition with invasive species certainly do not help its recovery chances. 

One of unique things about running buffalo clover is it's lack of nodulation. A lot of legumes have nodules where symbiotic Rhizobium bacteria reside and fix nitrogen. In a field study, there found no nodules on the roots of running buffalo clover and no significant nitrogen fixation rates. In comparison, white clover fixes a large amount of nitrogen (128 kg N/hectare/year) because of nodules containing Rhizobium. Was the lack of symbiosis always the case for running buffalo clover or has it's particular species of bacteria been lost to time? The answer to that question is unknown. 

Hopefully the next time you're on the hunt for a four leaf clover, you will now recognize running buffalo clover by using the tips above. They should be flowering right about now!

Diagrams from USDA-NRCS PLANTS Database / Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York. Vol. 2: 357-358

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