A tribute to Professor Curtis Strobeck, Conservation Geneticist

Abstract

In Graeme Caughley's (1994) pithy review of the field of conservation biology, population genetics is given substantial attention, but he concludes that genetic contributions to conservation are insufficiently based on data. Curtis Strobeck's career followed the path outlined by Caughley. His early work contributed to the theory of population genetics, and in his later years, he amassed a remarkable catalog of examples of how population genetics relates to conservation.

Curtis Strobeck died on 8 May 2025 at the age of 84 in Edmonton, Alberta. Curtis was professor emeritus in the Department of Biological Sciences at the University of Alberta and cofounder of Wildlife Genetics International (WGI) in Nelson, British Columbia. Curtis had an extraordinary influence on applications of quantitative and molecular genetics to conservation and trained over 20 graduate students during his 50-year career.

A native of Casper, Wyoming, Curtis attended Caltech in Mathematics and finished both a BA and MA in mathematics at the University of Montana in Missoula. He undertook his doctoral education during the heyday of theoretical ecology and evolution at the University of Chicago, receiving his PhD in theoretical biology in 1971. A brief postdoc with legendary Richard Lewontin at Chicago was followed by a 4-year fellowship with John Maynard Smith at the University of Sussex in England. After a year as an assistant professor at the State University of New York at Stony Brook, where he worked with George Williams, he was recruited by the University of Alberta as an associate professor and later was promoted to professor in 1983. He served at the University of Alberta until his retirement at 65 in 2005.

Curtis was a productive and influential scholar, publishing over 200 peer-reviewed papers, and he served on the editorial boards of Theoretical Population Biology, Evolution, and the Canadian Journal of Genetics and Cytology. His early work was theoretical and made important contributions to the ideas of n-species competition (Strobeck, 1973), selection in fine-grained environments (Strobeck, 1975), and gene hitchhiking (Strobeck et al., 1976). Brian Charlesworth commented that Curtis had “an unerring eye for exposing bullshit.” In later years, he focused on applications of molecular genetics to conservation, especially of mammals of northern North America.

Curtis’ most heavily cited paper was on fluctuating asymmetry (FA) with his colleague Rich Palmer (Palmer & Strobeck, 1986), who attributes the mathematical insights to Curtis. Their work synthesized a diverse array of approaches to quantifying FA and proposed an analytical approach—still widely used—to test whether true differences between sides were significantly greater than simple measurement error, which yields the same pattern of variation. Numerous applications in conservation biology have been suggested in which FA represents developmental instability and environmental stress. Curtis continued his fascination with the topic and he published follow-up papers (Palmer & Strobeck, 1992, 1997; Palmer et al., 1993) with Palmer that further refined analytical approaches to studying FA.

When I moved to the University of Alberta in 1999, Curtis was working on a paper with Garth Mowat on how to use mark–recapture methods with DNA from hair samples to estimate population size of grizzly bears (Mowat & Strobeck, 2000). This method has seen abundant application around the world, the sampling protocol for which was refined in 2004 (Boulanger et al., 2004) and more recently applied to spatially explicit capture recapture. These DNA methods generated enormous demand for DNA technology, and along with his former PhD student, David Paetkau, Curtis founded WGI in Nelson, British Columbia. After Curtis retired, he kept involved with science. He seldom missed departmental seminars, and he was delighted to serve as an external examiner for candidacy exams and thesis defenses for graduate students.

Curtis used molecular DNA methods to study spatial structuring and dynamics of the genomes of many taxa, including bears, wolves, mountain sheep, caribou, bison, seals, mustelids, and lynx. Extensive dispersal by lynx (Lynx canadensis) homogenizes much of the geographic variation among populations over vast areas of the North, calling into question local conservation measures (Campbell & Strobeck, 2006). In contrast, with Mike Proctor (Proctor et al., 2002), he documented that genetic drift had resulted in surprising differentiation among grizzly bear (Ursus arctos) populations, and the source of females could be identified by mitochondrial DNA on either side of Highway 3 in southern Alberta. Curtis and I participated in a workshop on wolves (Canis lupus) in Sweden in 2002 that focused on the consequences of small population size on wolf genetics and population recovery. It was clear that he was excited to learn about natural history, for example, from his participation in the genetics group for the endangered Peary caribou (Rangifer tarandus pearyi) on islands in the far north of Canada.

Bison genetics was an intriguing quagmire that Curtis unraveled. Based on experimental crossing of domestic cattle with bison in the early 20th century, Curtis found that most bison (Bison bison) herds in North America share mitochondrial DNA with cattle, including those in Custer State Park, which has been the source for many domesticated bison herds in the United States (Polziehn et al., 1995). When conservation has been a priority, the challenge for managers has been to find genetically pure stocks of bison, such as those in Yellowstone National Park, United States, and Elk Island National Park, Canada.

Professor Strobeck's theoretical contributions to population genetics provided insights that have rescued genetics from irrelevance to its proper place in conservation science. Curtis is survived by his daughter, Natasha Prepas-Strobeck, who studies microplastics at the University of Waterloo in Kitchener, Ontario.