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Biodiversity Blog


Featured Species: Fishes of Waller Creek and the Invasive Variable Platyfish (Xiphophorus variatus)

by Adam Cohen (Ichthyology Collection Manager) and Dean Hendrickson (Curator of Ichthyology)

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For the last 25 years, the Hendrickson Lab has been monitoring the fishes of Waller Creek, on the UT campus as well as the surrounding vicinity. Their specimen collections have usually included UT students, the public, or local schools, illustrating the value of this urban creek for environmental education. By comparing these data to those of UT Zoology graduate student Robert Edwards in the 1970s, we find that the dominant species have not changed, but unfortunately, at least five native species that were rare in the 70s are now gone. We also have a new invasive, albeit beautiful, species from northern Mexico – the Variable Platyfish (Xiphophorus variatus), that is now often the most common species. It will likely never be known how it first arrived, but it is suspected to have been released from someone’s aquarium. First collected in 2004 at 24th street, we’ve now documented its spread from the mouth in Ladybird Lake to the headwaters at Denson Drive.

The environmental impact of this species in the creek is uncertain, but may be substantial, and it’s likely the species could spread beyond Waller Creek where its impacts could be even greater. One possible area is Barton Springs, little more than a mile from the mouth of Waller across Ladybird Lake. The presence of this species could provide interesting research opportunities, and coincidently UT has lots of experience with its close relatives. Several other labs in the Department of Integrative Biology (the lab of Dr. Molly Cummings and the lab of Dr. Michael Ryan) have long been doing behavioral research on other species of the genus or family (Poeciliidae). Furthermore, the species is used as a model organism in cancer research.

Unfortunately, earlier collections were rare and not well documented, but we suspect the creek’s fish community was originally more diverse than our data reveals. As much as we’d like to, we can’t go back in time to confirm this. However, going forward with funding from UTs Green fee program, the Hendrickson Lab and other researchers interested in the creek are regularly monitoring the creek’s biota and abiotic factors such as temperature and water chemistry, and documenting what is living there via photography on our iNaturalist Project as well as specimens deposited into UT’s Biodiversity Collections. Thus, future researchers and conservationists will have a long history of collections of physical specimens and a growing diversity of environmental data at their disposal. This will assist with diverse research or for decision-making about creek zone management. As part of our effort to promote interest and research in the creek, we established a permanent searchable archive on UT Libraries’ Texas Scholar Works where we have deposited all of the data, reports, and articles that we could find relating in any way to Waller Creek, and where we hope all new research data will also be deposited.

The second Waller Creek Symposium will be held on Monday, May 7th, where we will present a poster that expounds on what’s presented in this blog post, and many others will be presenting their diverse information about the creek. If this is of interest, you are encouraged to attend! The symposium starts at 9:30 a.m. on Monday, May7th, at the UT Recreational Sports Center. For more details, visit this link.

More about Waller Creek’s fish fauna is available through our Fishes of Texas Project, and we encourage everyone who passes across or through the Waller Creek corridor to submit their own organismal photo observations, or see what’s been submitted by others, in our Waller Creek iNaturalist Project.

Explorer and Botanist: Mary Sophie Young
Focus on Biology - 2018 Integrative Biology Image ...

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