This is a story about how historically valuable museum specimens coupled with state-of-the-art DNA sequencing present new frontiers for research.
In 1871, Edward Drinker Cope described Salmo stomias (currently valid as Oncorhynchus clarkii stomias, greenback cutthroat trout) based on syntype specimens in the Academy’s fish collection. Those two specimens now have yielded DNA to a team of researchers.
Working at the University of Colorado, Boulder, and at the Australian Centre for Ancient DNA, CU postdoctoral scientist Jessica Metcalf led the team that recovered DNA sequence data for fragments of two mitochondrial genes (ND2 and CO1). Analysis of the DNA sequence data from the Academy syntypes, along with important documents recovered from Academy Archives (with help from Clare Flemming and Megan Gibes) helped resolve a longstanding mystery surrounding the origin of Cope’s cutthroat trout.
First, it is reasonably clear that the syntypes were collected and sent to the Academy by William Alexander Hammond (1828–1900), Abraham Lincoln’s surgeon general during the Civil War and founder of the Army Medical Museum (now the National Museum of Health and Medicine). Cope assumed that the cutthroats, like other Hammond specimens sent to the Academy, were collected while Hammond served as surgeon on an Army expedition under the command of Lt. Francis T. Bryan.
Bryan’s expedition traveled from Fort Riley, Kan., to Fort Bridger, Wyo., and back again in 1857 (and was preceded by a similar expedition in 1856, though unaccompanied by Hammond). The oldest label associated with the specimens indicates “Fort Riley, Kansas” and their origin subsequently became associated with the headwaters of the South Platte River in Colorado.
The DNA sequence data, however, groups Hammond’s cutthroats with the Rio Grande cutthroat, Oncorhynchus clarkii virginalis, sampled from New Mexico. Hammond’s field notes and correspondences in the Academy Archives confirm that he: 1) never entered the South Platte River drainage during Bryan’s 1857 expedition, but instead traveled through the troutless waters of the Laramie plain and North Platte River in Wyoming, and 2) was stationed as a medical doctor near Sante Fe from 1849 to 1852.
In a letter to Leidy dated June 1855, Hammond confided that he was headed back to Santa Fe with a topographical survey. A subsequent letter to John Le Conte, dated May 12, 1856, suggests that samples collected on that trip to New Mexico were sent to the Academy in 1856.
Based on the DNA sequence data and Hammond’s letters, the Academy syntypes of Cope’s greenback cutthroat appear to have originated from tributaries of the Rio Grande near Santa Fe around 1855-1856, not the upper South Platte River in Colorado. That relocation has muddled the nomenclature of cutthroats.
Technically, Cope’s (1871) cutthroat, Oncorhynchus clarkii stomias, is a junior synonym of Girard’s (1856) Oncorhynchus clarkii virginalis, the scientific name in use for the Rio Grande cutthroat trout. In other words, Cope’s scientific name is neither valid, nor applicable to South Platte River cutthroats. However, Cope’s name stomias has long been used for the South Platte River trout, commonly known as the greenback cutthroat and, incidentally, Colorado’s state fish.
Furthermore, the greenback cutthroat was thought to have gone extinct in 1937. But Jessica Metcalf and her team identified a single surviving population of greenbacks in Bear Creek (Arkansas River Basin) based on DNA comparisons of modern cutthroats to historical specimens in other museums.
It remains uncertain whether the scientific name stomias will be applied to the Bear Creek population in Colorado. Based on their DNA fingerprints, the type specimens of Cope’s Oncorhynchus clarkii stomias are neither greenback cutthroats, nor from Colorado.
The results of the cutthroat research appear in several recently published scientific articles (Metcalf et al., 2007; 2012) and a popular article in Colorado Outdoors (Rogers, 2012). Their work is a remarkable example of how old, historically valuable museum specimens coupled with state-of-the-art DNA sequencing technology present new frontiers for taxonomic and systematic research, not unlike those presented by the West to explorers like Hammond and Bryan.
By Mark Sabaj, Academy Interim Curator of Ichthyology
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In the Academy’s “Spotlight on the Collections” series, we tell stories about specimens chosen by our scientists and also how researchers and others around the world depend on our collections for issues involving climate change, water quality, evolution, and biodiversity and extinction.
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