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Biodiversity Blog

 

CAMPUS BIODIVERSITY: Urban Orchids

 Corallorhiza wisteriana patch

For the observant visitor to the UT-Austin campus, the 40 Acres sometimes reveal botanical treasures.  For example, not many local inhabitants are aware that the campus harbors native wild orchids. In recent weeks, the spring coral root orchids, Corallorhiza wisteriana have been experiencing an exceptionally good bloom. 

Corallorhiza wisteriana is widespread in the United States and the mountains of adjacent Mexico, but, like many orchids, it is nowhere very common within its large range. By wildflower standards, these orchids are not particularly showy, except when the flowers are magnified with a hand-lens, revealing the subtle beauty of the arched sepals and the spotted lip which serves as a landing pad for pollinators like bees and flies.

Most orchids have connections to soil-borne fungi known as mycorrhizal associations. These same fungi frequently also are connected to nearby tree species. The plants are able to get water and nutrients through the expanded below-ground surface area, and the plant roots provide a stable, moist environment for the fungi to function in during dry times.

However, the genus Corallorhiza has taken this process one step further and its species are entirely lacking in chlorophyll. This means they derive all of their water and nutrients parasitically from the fungus. Such mycotrophic plants are sometimes also called secondary plant parasites, as nutrients can move from surrounding woody “hosts” through the fungi, and into the parasite.  Because they lack chlorophyll but produce abundant anthocyanin pigments, coral root plants usually have a dark purple to maroon color, and the leaves have become reduced to a few small scale-like structures on the stems.

 Corallorhiza wisteriana specimen

On campus, the patch of coral roots emerges each year from among the ground covers in the shade under a huge live oak near 24th and Guadalupe. Thousands of students, staff, faculty, and visitors walk by them every day, but only the observant passerby ever notices these small beauties, and many who see the plants do not know they are orchids.

Despite its relative obscurity, this plant is no newcomer to campus. When Doug Goldman was a doctoral student in Plant Sciences at UT, he learned about the campus population. In 1997, he documented it with a specimen now housed in the University of Texas Herbarium at the Billie L. Turner Plant Resources Center. This specimen indicates Corallorhiza wisteriana has been present at this particular location for more than two decades and likely for a much longer time.

Specimens like this in the Herbaria serve as important time capsules that provide historical context to biodiversity observations and physical artifacts to document the distributions of species. The UT Biodiversity Center includes extensive biological resource collections that record the flora and fauna of Texas and the world in time and space.

George Yatskievych is a Curator in the Billie L. Turner Plant Resources Center in the Biodiversity Center

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