In 1861, American Physician and Naturalist James Graham Cooper described a new species of tortoise from the deserts of California, and a 150-year mystery began. He named this new discovery Agassiz’s Land Tortoise (Gopherus agassizii), but the name was changed some years later to Desert Tortoise. Fast forward 140 years later to a review that was published in 2002 on the conservation of the Desert Tortoise and the status of existing populations. It summarized evidence that Gopherus agassizii was not a single species, but was actually two to four species. Subsequent research by Dr. Bob Murphy, ROM Senior Curator of Herpetology, and the Kunming Institute of Zoology, Chinese Academy of Sciences, and colleagues from the US Geological Survey, Arizona Research Laboratories, California Academy of Sciences, and Lincoln University, confirmed that the United States populations of Desert Tortoise are in fact two species.
The procedures Dr. Murphy and his colleagues used in unravelling this mystery are a testament to the importance of museum specimens and the application of cutting-edge molecular genetics analyses to assist in the conservation of endangered species. The original description of Gopherus agassizii by Cooper was based on three juvenile specimens that he stated were found “in the mountains of California near Fort Mohave,” Arizona, and the species was described in the scientific literature as being from Arizona. During an investigation into the population genetics of the Desert Tortoise, DNA was obtained from the original 150-year-old type specimen in the Smithsonian Institution for comparison with hundreds of specimens from the Southwest plus another species of Gopherus from Baja California that shared similar morphological characteristics and habitat preferences. The analyses revealed that G. agassizii was originally from California, not Arizona, as sometimes claimed. An investigation into the historical literature surrounding Cooper’s original report describing the species revealed that the specimens were likely collected around Soda Lake in California. What this means is that the populations of Gopherus east of the Colorado River in Arizona and adjacent Mexico were not Gopherus agassizii, but a different, then un-named species. The new species has now been named Gopherus morafkai, after a pioneer in tortoise research, the late David J. Morafka.
What this also means is that the range of Agassiz’s Desert Tortoise has now shrunk by 70% – this species exists west of the Colorado River only. The conservation implications are huge as Gopherus agassizii has already experience a drastic decline in the number of individuals because of disease, urban expansion, and habitat destruction. It is currently listed as threatened and faces increasing pressure from construction of solar development sites in its Mohave Desert habitat. Perhaps its status should be upgraded to endangered? This would facilitate stronger protective legislation that is needed to ensure that the species does not suffer a further decline, only to be on the brink of extinction merely 150 years after it was first discovered.
Murphy, Robert W. et el. “The dazed and confused identity of Agassiz’s land tortoise, Gopherus agassizii (Testudines, Testudinidae) with the description of a new species, and its consequences for conservation.” Zookeys, 113: 39 – 71.