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Gottscho, Andrew



Smithsonian Institution

National Museum of Natural History

Washington, DC USA


Current address:

10x Genomics,

Pleasanton, California USA


The Colorado Desert, where the Colorado River meets the San Andreas Fault system (Salton Trough), is home to iconic lineages of lizards found nowhere else on Earth. Including the hottest and driest lands in California, Baja California, Arizona, and Sonora, this desert extends approximately from the Coachella Valley to the Gulf of California. Multiple species of fringe-toed lizards (genus Uma) have been described from this region, including the Coachella Valley fringe-toed lizard (Uma inornata) and the Mohawk Dunes fringe-toed lizard (Uma thurmanae). Uma are specialized for wind-blown sand substrates, and different dune systems are effectively islands to Uma. Flat-tailed Horned Lizards (Phrynosoma mcallii) also range from the Coachella Valley to the Gulf, but are represented by only a single species. Why has Uma apparently speciated here while P. mcallii has not? Now we have two published, highly comparable genomic datasets, collected using nearly identical ddRADseq protocols and with similar sampling across the Colorado Desert, for both Uma and P. mcallii (Gottscho et al. 2017, 2024). Phylogenetic and clustering algorithms reveal similar patterns in both lineages, but there are also key differences. For P. mcallii, there is evidence for a very severe, very recent population bottleneck, and for hybridization with parapatric Phrynosoma species. Potential conservation implications will be discussed, as U. inornata is a federally threatened species, and P. mcallii is the subject of a long-standing Rangewide Management Strategy.

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