As a travel destination, the Big Bend has a long list of passionate partisans. Outdoors adventurers come for the mountain trails and remote canyons, art-world cognoscenti for Donald Judd’s work, Old West enthusiasts for the cowboy poetry.
Then, there are the “herpers.”
Trans-Pecos Texas has a stunning diversity of reptiles and amphibians, and herpetologists, both professional and avocational, flock here from around the world.
Now, researchers are turning their attention to one example of that diversity – a mysterious lizard known as the Dixon’s whiptail.
Dr. Corey Roelke is a professor at UT-Arlington.
“The questions kind of never end with whiptails,” Roelke said. “There's just a lot of good questions to answer, and they're excellent study organisms.”
An Indiana native, Roelke knew by age 10 he wanted to be a herpetologist, and to work in Texas.
West Texas is rich in whiptail lizards. Slender-bodied and long-tailed, they race and dart across the desert floor on blazing summer days, hunting insects. Diverse species typically stick to specific niches – defined by elevation, slope and other factors. But, apparently, those boundaries don’t always hold.
“Occasionally you get these accidents where two species hybridize,” Roelke said, “and when they hybridize, a lot of times they produce a new species, and that new species becomes asexual. So at that point, they're all female and they produce clones of themselves.”
In 1973, researchers in the Chinati Mountains found the product of one of these “accidents.” Named for a famed Texan herpetologist, the Dixon’s whiptail appeared to be a hybrid of two common species – the marbled whiptail and the rusty-rumped whiptail. The lizard has since been spotted in only one other locale, a tiny area in the New Mexico bootheel.
Now, Roelke and his colleague Matthew Fujita have received a Texas Parks & Wildlife grant to study the creatures. Next summer, they’ll be out in the Chinatis with “lizard lassos” – long poles with tiny loops – hoping to catch 15 to 20 Dixon’s whiptails.
They’ll try to estimate the population size. And, after euthanizing captured lizards, they’ll analyze their DNA – with cutting-edge techniques that were unavailable to their scientific predecessors.
“Our tools to look at the genomes of these lizards are so much more powerful than they were even 10 years ago,” Roelke said. “So we can essentially sequence entire genomes of these lizards and much more cheaply than we used to be able to.”
That DNA analysis will reveal if the Dixon’s whiptail is in fact a distinct species. If that’s the case, these lizards are certainly rare, and they might be eligible for listing as an endangered species.
Roelke and his colleagues have noted two “pattern classes” – two groups of Dixon’s whiptails with slightly different characteristics. Each group, Roelke said, is likely the result of a single instance of interbreeding.
These lizards have endured in the Chinatis as a female-only population for untold years. But their future isn’t guaranteed, Roelke said. Their kin – the marbled whiptails – are an aggressive bunch, and can outcompete the Dixon’s for resources.
Marbled whiptails favor low, hot deserts. But as the West Texas climate warms and dries, they’re moving into higher elevations. And that could press the Dixon’s whiptails further into the stony heights of the Chinatis.
“Well, at some point,” Roelke said, “and this is a problem for lots of mountain-dwelling reptiles and amphibians and mammals and birds, is that you eventually may run out of mountain.”
Amidst the desert immensity, the Big Bend contains a hidden diversity of landscapes and habitats. And as the Dixon’s whiptail shows, it also contains a hidden diversity of inhabitants.
