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The University of Texas at ArlingtonThe University of Texas at Arlington

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Department of Biology News

Roelke, Fujita using TPWD grant to study imperiled reptile

Matthew Fujita and Corey Roelke with a photo of a spot-tailed earless lizard and DNA sequencing data.

Biologists from The University of Texas at Arlington are studying a species of lizard found in parts of Texas and northeastern Mexico to find out why the reptile’s numbers have been dwindling dramatically.

They are conducting fieldwork and genome sequencing to learn as much as possible about the spot-tailed earless lizard (Holbrookia lacerata), which has experienced a steady decline in population in Central and South Texas. The work is being supported by a two-year, $130,880 grant from the Texas Parks & Wildlife Department. Corey Roelke, a lecturer in biology, is principal investigator (PI) of the project; Matthew Fujita, an assistant professor of biology, is co-PI.

“We propose a comprehensive study in the natural history, morphology, phylogenetics, and ecological genetics of H. laceratain order to provide a thorough assessment on the conservation and management priorities for an imperiled species,” Roelke wrote in the project abstract.

In addition to Central and South Texas, the spot tailed earless lizard is found in the Mexican states of Nuevo León, Taumalipas and Chihuahua. Its habitat is typically flat, arid and open. It has declined in both its distribution and abundance, particularly in South Texas.

In some southern Texas counties where the lizard has been documented, it had not been seen in over 30 years until the past 12 months, when specimens were found in several places in South Texas. The lizard is not protected by either the state of Texas or the U.S. Fish and Wildlife Service.

“The goal is to learn as much as we can about the spot-tailed lizard because of its rapid decline in central and southern Texas,” Fujita said. “We need to quantify the sizes of their populations in addition to identifying any interactions among populations in order to assess the viability and persistence of this species.”

Fujita and Roelke are joined on the project by researchers from the University of Texas at Austin and Texas A&M University, who are largely conducting field-based surveys of the lizard. Gene sequencing of the samples is being done in Fujita’s laboratory.

“This collaboration will dramatically increase our sample sizes for more powerful genetic-based inferences of population size, migration rates, and genetic diversity,” Roelke said.

For the last two years, Roelke and Fujita have done fieldwork to collect the lizard and its close relatives within the genus Holbrookia. Fujita’s lab has taken the specimens and sequenced the transcriptomes - which are collections of all the gene readouts present in a cell - along with some basic genetic markers to begin quantifying genetic diversity.

“So far, we have sequenced the transcriptomes, or the complete catalog of actively transcribed genes, for the spot-tailed lizard as the first major step in quantifying the genetic variation in this lizard,” Fujita said. “This resource will be invaluable in pursuing the population genetics as soon as more fieldwork is done this year.”

Roelke and Fujita plan to return to Central and South Texas in the coming months to conduct field assessments, take detailed natural history notes, and collect data and more samples to create a comprehensive natural history profile of the lizard.

They hope to answer questions such as what habitat requirements are necessary for local and range-wide population viability; where the lizard’s population is most dense; whether subpopulations of H. lacerataexchange genetic material; and how distinct H. lacerata is from other species of Holbrookia.

The questions are important because the Central and South Texas populations of H. lacerata have distinct morphological differences and may represent distinct species, necessitating different conservation priorities and management plans, Roelke said.

While the factors causing the lizard’s dwindling numbers are unknown, at least some of the decline is likely due to anthropogenic - meaning caused by human activity - habitat change. Potential threats include the use of agricultural herbicides and insecticides; loss of habitat and habitat fragmentation due to conversion of land to agriculture use or road construction. There is a lack of detailed knowledge of the natural history, phylogenetics, and population biology of Holbrookia laceratathat can impart fundamental insight into the best methods of conservation and preservation of the species, Roelke said.

The field work this spring will be followed by more genome sequencing in Fujita’s lab in order to provide a phylogenetic context of the lizard’s evolution; to test whether the Central and South Texas populations are distinct species; and to quantify demographic parameters, including population sizes and gene flow between the Central and South Texas populations.

“These will have important conservation implications,” Roelke said. “These inferences will provide the necessary data and context to recommend a conservation management plan that works to benefit the lizard and private landowners. It’s an interesting project because this is a lizard that has declined greatly and unfortunately, we really don’t know why.”