Dr. John Demboski is an evolutionary biologist who studies how different processes—abiotic and biotic—contribute to diversity in western North American mammals. He combines fieldwork and genetics to look into the basic questions about how and why species diverge and occur where they do. Though John has worked on a variety of small mammals, his primary focus over the last 20 years has been on chipmunks and shrews. He has conducted fieldwork across all the western states and in Canada, Mexico, Mongolia, Paraguay, the Philippines, and Russia. John was born in Hawaii and lived all over the United States before heading off to Purdue University for his BS. An opportunity to volunteer behind the scenes at the Cincinnati Museum of Natural History culminating in an expedition to the Philippines in 1992, led him to the Far North where he received his PhD at the University of Alaska Fairbanks. During that time, he worked extensively in the University of Alaska Museum’s mammal collections. After postdoctoral positions at the University of Idaho and Louisiana State University, John was an assistant professor at the California State Polytechnic University, Pomona. He then landed at DMNS where he has been curator of mammals since 2006. During his time in Denver, he has more than doubled the size of the mammal collections and started new collections in parasites and frozen tissues.
I have been working on a truly fascinating and diverse group of mammals—western chipmunks—over the last 20 years. There are 23 species and extensive diversity within each species. The research has focused on many aspects of their evolutionary biology through extensive fieldwork, genetics and genomics, morphology, and parasites. This has included unraveling phylogenetic relationships among the 23 species, identifying potentially new species, examining the phylogeography of individual species, assessing hybridization between some of the species, investigating genital bone diversity and evolution, understanding co-divergence of chipmunks and some of their parasites (sucking lice, nematodes), learning more about their basic natural history and distribution, and recently, exploring the possibility of phylosymbiosis (similarity between microbiomes mirrors the evolutionary relatedness of the hosts) in chipmunks. None of this would have been possible without the efforts of my long-term collaborators and their students, including Jack Sullivan (University of Idaho), Jeff Good (University of Montana), Kayce Bell (Natural History Museum of Los Angeles County), and funding from the Denver Museum of Nature & Science and the National Science Foundation (#0716200).
Herrera, ND, KC Bell, CM Callahan, E Nordquist, BAJ Sarver, J Sullivan, JR Demboski, and JM Good. (2022) Genomic resolution of cryptic species diversity in chipmunks. bioRxiv 10.1101/2022.02.28.482304
Sarver B. A. J., N. D. Herrera, D. Sneddon, S. L. Hunter, M. L. Settles, Z. Kroneneberg, J. R. Demboski, J. M. Good, and J. Sullivan (2021) Diversification, Introgression, and Rampant Cytonuclear Discordance in Rocky Mountains Chipmunks (Sciuridae: Tamias).Systematic Biology. 10.1093/sysbio/syaa085
Bell K. C., J. M. Allen, K. P. Johnson, J. R. Demboski, and J. A. Cook. 2020. Disentangling lousy relationships: comparative phylogenomics of two sucking louse lineages parasitizing chipmunks. Molecular Phylogenetics and Evolution. 10.1016/j.ympev.2020.106998
Grond, K., K. C. Bell, J. R. Demboski, M. Santos, J. Sullivan, and S. M. Hird. 2019. No evidence for phylosymbiosis in western chipmunk species. FEMS Microbiology Ecology. fiz182. DOI: 10.1093/femsec/fiz182.
Bell, K. C., J. R. Demboski, and J. A. Cook. 2018. Sympatric parasites have similar host-associated, but asynchronous, patterns of diversification. American Naturalist 192(3):E106–E119. DOI: 10.1086/698300
Pigage, H. K., J. C. Pigage, and J. R. Demboski. 2017. Siphonaptera of North American western chipmunks. Comparative Parasitology 84(2):135–141. DIO: 10.1654/1525-2647-84.2.135
Sarver, B. A. J., J. R. Demboski, J. M. Good, N. Forshee, S. L. Hunter, and J. Sullivan. 2017. Comparative phylogenomic assessment of mitochondrial introgression among several species of chipmunks (Tamias). Genome Biology and Evolution 9(1):7–19. DOI: 10.1093/gbe/evw254
Bell, K. C., K. Calhoun, E. P. Hoberg, J. R. Demboski, and J. A. Cook. 2016. Temporal and spatial mosaics: deep host association and shallow geographic drivers shape genetic structure in a widespread pinworm, Rauschtineria eutamii (Nematoda: Oxyuridae). Biological Journal of the Linnean Society 119(2):397–413. DOI: 10.1111/bij.12833
Bell, K. C., D. Matek, J. R. Demboski, and J. A. Cook. 2015. Expanded host range of sucking lice and pinworms in Western North American chipmunks. Comparative Parasitology 82(2):312–321. DOI: 10.1654/4756.1
Sullivan, J., J. R. Demboski, K. C. Bell, S. Hird, B. Sarver, N. Reid, and J. M. Good. 2014. Divergence with gene flow within the recent chipmunk radiation (Tamias). Heredity 113(3):185–194. DOI: 10.1038/hdy.2014.27
Reid, N., J. R. Demboski, and J. Sullivan. 2012. Phylogeny estimation of the radiation of Western North American chipmunks (Tamias) in the face of introgression using reproductive protein genes. Systematic Biology 61(1):44–62. DOI: 10.1093/sysbio/syr094
Hird, S., N. Reid, J. Demboski, and J. Sullivan. 2010. Introgression at differentially aged hybrid zones in red-tailed chipmunks. Genetica 138(8):869–883. DOI: 10.1007/s10709-010-9470-z
Good, J. M., S. Hird, N. Reid, J. R. Demboski, S. J. Steppan, T. R. Martin-Nims, and J. Sullivan. 2008. Ancient hybridization and mitochondrial capture between two species of chipmunks (Tamias: Rodentia). Molecular Ecology 17(5):1313–1327. DOI: 10.1111/j.1365-294X.2007.03640.x
Good, J. M., J. R. Demboski, D. W. Nagorsen, and J. Sullivan. 2003. Phylogeography and introgressive hybridization: chipmunks (genus Tamias) in the northern Rocky Mountains. Evolution 57(8):1900–1916. DOI: 10.1111/j.0014-3820.2003.tb00597.x.
Demboski, J. R., and J. M. Sullivan. 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. DOI: 10.1016/S1055-7903(02)00363-9
I have recently begun to work again on shrews, small mammals that formed the basis of my PhD dissertation in the 1990s. In particular, I examined two species groups of red-toothed shrews (Sorex) that occur in western North America, including some species spilling over into Far East Asia. The cinereus and vagrans groups consist of multiple species of shrews with extensive cryptic genetic diversity, which in some instances might represent new species and possess some very interesting phylogeographic patterns. More recently, in collaboration with Andrew Hope (Kansas State University), we examined North America’s smallest mammal, the pygmy shrew (Sorex hoyi), which weighs in at 2 to 4 grams and is widely distributed across the North American boreal forest biome. An isolated population, S. h. montanus, also occurs in Colorado and Wyoming above 2,800 meters.
Shrews can be very difficult to identify; commonly, characteristics of the teeth, particularly the size and number of unicuspids (one-cusp teeth), are diagnostic. However, this approach can be ambiguous and doesn’t account for underlying cryptic diversity. To this end, we’ve begun to “DNA Barcode” shrews in the Denver Museum of Nature & Science mammal collection. This work is being conducted in the Genetics Lab and will involve our community scientists. This will allow us to definitively identify the specimens in our collection and generate preliminary genetic data.
Hope, A. G., R. S. Stephens, S. D. Mueller, V. V. Tkach, and J. R. Demboski. 2019. Speciation of North American pygmy shrews (Eulipotyphlya: Soricidae) supports spatial but not temporal congruence of diversification among boreal species. Biological Journal of the Linnean Society. blz139. DOI: 10.1093/biolinnean/blz139
Hope, A. G., K. A. Speer, J. R. Demboski, S. L. Talbot, and J. A. Cook. 2012. A climate for speciation: rapid spatial diversification within the Sorex cinereus complex of shrews. Molecular Phylogenetics and Evolution 64(3):671–684. DOI: 10.1016/j.ympev.2012.05.021
Demboski, J. R., and J. A. Cook. 2003. Phylogenetic diversification within the Sorex cinereus group (Soricidae). Journal of Mammalogy 84(1):144–158. DOI: 10.1644/1545-1542(2003)084.
Demboski, J. R., and J. A. Cook. 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. DOI: 10.1046/j.1365-294x.2001.01260.x.
Demboski, J. R., K. D. Stone, and J. A. Cook. 1999. Further perspectives on the Haida Gwaii glacial refugium. Evolution 53(6):2008–2012. DOI: 10.1111/j.1558-5646.1999.tb04584.x.