John Demboski, PhD

Dr. John Demboski is an evolutionary biologist that studies how different processes -- like climate and geological change, gene flow/hybridization, and speciation -- create diversity in western North American mammals. He combines fieldwork and lab work to look into the basic questions about how and why species occur where they do.

  • POSITIONCurator of Vertebrate Zoology
  • EXPERTISE Evolutionary biology
  • PhD

    University of Alaska Fairbanks

  • PHONE NUMBER303.370.6443
  • EMAIL[email protected]
  • RESUME Click to Download
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  • 1

    Hird, S., Reid, N., Demboski, J.R, and Sullivan, J. 2010. Introgression at differentially aged hybrid zones in red-tailed chipmunks. Genetica, 138(8):869-883.

  • 2

    Good, J.M., Hird, S., Reid, N., Demboski, J.R., Steppan, S.J., Martin-Nims, T.R. and Sullivan, J. 2008. Ancient hybridization and mitochondrial capture between two species of chipmunks. Molecular Ecology, 17(5): 1313-1327.

  • 3

    Carstens, B.C., Brunsfeld, S.J., Demboski, J.R., Good, J.A., and Sullivan, J.M. 2005. Investigating the evolutionary history of the Pacific Northwest mesic forest ecosystem: Hypothesis testing within a comparative phylogeographic framework. Evolution, 59(8):1639-1652.

  • 4

    Demboski, J.R. and Sullivan J.M. 2003. Extensive mtDNA variation within the yellow-pine chipmunk, Tamias amoenus (Rodentia: Sciuridae), and phylogeographic inferences for northwest North America. Molecular Phylogenetics and Evolution, 26(3):389-408.

  • 5

    Demboski, J.R. and Cook, J.A. 2001. Phylogeography of the dusky shrew, Sorex monticolus (Insectivora, Soricidae): Insight into deep and shallow history in northwestern North America. Molecular Ecology, 10(5):1227-1240.


A Comprehensive Multigene Phylogeny of Chipmunks (Rodentia: Tamias): Testing Divergence with Gene Flow

What is a species? The "biological species concept" defines a species as members of a population that are capable of interbreeding. But according to Dr. John Demboski of the Denver Museum of Nature & Science, this is not entirely accurate.

"It's not as easy as what you learned in your high school text book," Dr. Demboski said, explaining that the theory does not accommodate asexual organisms or interbreeding between distinct species like wolves and coyotes.

Dr. Demboski and collaborator Dr. Jack Sullivan of the University of Idaho aim to solidify the term "species" through a comprehensive study of the phylogeny -- or evolutionary tree -- of chipmunks, which are small ground squirrels. According to Dr. Demboski, western chipmunks are a great study system because they are a recently evolved group that still appears to be in the middle of speciating-the process through which new species arise.

"Chipmunks give us a snapshot of the process," Dr. Demboski said.

Chipmunks are among the most diverse mammals in the West with 23 currently defined species and extensive diversity within species. Many chipmunks partition into distinct habitats or niches to minimize competition between species. Some of these habitats overlap, however, creating contact zones where different species meet and potentially interbreed. When this occurs and chipmunk species exchange genes, it creates a complex family tree.

"Because chipmunks tend to be very similar in appearance, it can be difficult to figure out how these 23 species are related to each other and how they came to be so diverse in the West," Dr. Demboski said.

But there is one way to tell them apart: chipmunk species have very distinct genital bones.  This has been thought to promote reproductive isolation among species through a "lock and key" mechanism. However, as Dr. Demboski and his colleagues have discovered, interbreeding still occurs.

"We have identified numerous instances where gene flow occurs between ecologically and anatomically distinct species, suggesting hybridization may be important during the evolution of this and other groups," Dr. Demboski said.

Hybridization in chipmunks is not easy to detect. Dr. Demboski uses genetic data (e.g., DNA sequences) to identify the otherwise cryptic occurrences.  Molecular techniques can also be used to date hybrid events and determine the lineage of individual specimens.

Over the last 10 years, Dr. Demboski has collected specimens in 12 western states and Canada, discovered new hybrid zones (one in Colorado's Front Range), and uncovered previously unknown genetic diversity in chipmunks, possibly including new species.


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