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A top-notch blotch

Common side-blotched lizards (Uta stansburiana) are a ubiquitous lizard of the North American deserts. These lizards inhabit an extraordinarily broad range across the United States and northern Mexico from California’s Channel Islands to central Texas, and from the southern tip of Baja California to central Washington state. Throughout this range, these lizards demonstrate a wide variety of colors and patterns on their back, likely to better blend in with the diverse backgrounds where they live. In fact, these lizards are often a critical food source for other desert species and are sometimes referred to as the “food of the desert.”

Female side-blotched lizard (Uta stansburiana) by Samuel Fellows

This species is best known for alternative mating strategies associated with throat color in both male and female lizards in some populations. Orange-throated females lay many small eggs while yellow- and blue-throated females lay fewer but larger eggs. Male lizards, in contrast, demonstrate a “rock-paper-scissors” strategy where orange-throated males singly guard a harem of females, blue-throated males cooperatively guard a small group of females, and yellow-throated males sneak into harems guarded by the orange-throated males to mate. Orange-throated males out-compete blue-throated males, blue-throated males out-compete yellow-throated males, and yellow-throated males out-compete orange-throated males.

These evolutionarily stable strategies make common side-blotched lizards an excellent species in which to begin to understand the ways in which these alternative throat colors, mating strategies, and background-matching patterns can persist within and among populations in the same species. They also can help understand the ways in which these same factors promote speciation. This genome will help reveal the genetic underpinnings for throat color, mating strategy, and the beginning stages of speciation.

Today, we release the chromosome-length assembly for the side-blotched lizards (Uta stansburiana). The draft assembly was generated by Sam Fellows and Dr. Danielle Edwards using long-read sequencing data generated by the University of California Davis DNA Technologies and Expression Analysis core on two Pacific Biosciences Sequel II SMRT-cells, and was assembled with Hifiasm (Cheng et al. 2021). The Hi-C data was generated by DNA Zoo and applied to upgrade the draft to chromosome-length using methods described here.

The sample used for this genome assembly came from an orange-throated male from Wright’s Point, Harney County, Oregon, U.S.A. collected by Dr. Pete Zani. The animal comes from a large population of common side-blotched lizards that occupies sagebrush-steppe habitat in the northern Great Basin. The population persists on a volcanic lava flow surrounded on three sides by the Malheur wetlands national wildlife refuge. This population has been the subject of an 18-year long mark-recapture study which has demonstrated that lizards at this site are much longer-lived than those farther south (up to 7 years, in contrast to 1-2 years elsewhere), and that lizards at this location do not demonstrate the rock-paper-scissors mating behaviors associated with other populations.

Check out the 17 chromosomes (2n=34) of the common side-blotched lizard in the interactive Juicebox.js session below, and find out more information about the new reference on the corresponding assembly page.

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