College of Natural & Agricultural Sciences

Boris Bar

Boris Claude Bar

Professor of Entomology

1996-2000 PhD in Biology, ETH Zurich, Switzerland: “The importance of genetic variability as a defence against parasites”; supervisor Professor Paul Schmid-Hempel. 

1994-1995 Masters in Biology (Diploma), University of Zurich, Switzerland and Muséum National d’Histoire Naturelle, Paris: “Feeding ecology of the red handed tamarin (Saguinus midas midas) in tropical rainforest of French Guyana”; supervision Professor Hans-Ulrich Reyer and Professor Robert Martin. 

1990-1993 Undergraduate studies in Biology, University of Zurich, Switzerland.

Research Areas

Interested in the study of evolutionary processes such as immune and stress response as well as sexual conflicts on the molecular/protein scale.

Contact Information
283 Entomology Bldg
(951) 827-5833

I have used honeybees, leaf cutting ants and bumblebees to study aspects of social insect reproduction and immunity. To do this I pursue an integrative approach, which combines biochemical technologies such as proteomics and evolutionary biology. An important part of my work is to conduct biochemical analyses and to use their outcomes to formulate hypotheses that can be experimentally tested in the field. My idea is to help building a new field of research, which I refer to as evolutionary proteomics. Evolutionary proteomics will not only aim to understand evolutionary processes at the protein level, but will also attempt to quantify variations in proteomic profiles and investigate their consequences for natural and sexual selection.  I am specifically interested in the proteomic mechanisms underlying self-non-self recognition systems in honeybees and leaf-cutting ants, and will continue to address how transcriptional and translational modifications translate into protein-level mechanisms for discrimination against non-self agents such as microbial and protozoan parasites or ejaculates of competing males during insemination. Such knowledge will be of fundamental significance, but will also be applied in new breeding programs for honeybee stock improvement in collaboration with beekeepers in California and Western Australia. My overall goal is to develop a scientifically-guided breeding program that selects for honeybee lineages that are tolerant against diseases and more versatile in coping with environmental stressors. The species I use for my work  are all ideal model species for such work as they can be kept in the lab and the availability of techniques such as artificial insemination allow sophisticated experimental manipulations.

Awards Received

Australian Bee Industry Award (2016). 

The Premier’s Science Award of Western Australia (2014). 

Swiss Award, Swiss Australian Chamber for Commerce and Industry (2013). 

"Busy Bee" award by the Western Australian Apiarists Association (2012). 

ETH silver medal for exceptional PhD Thesis (2001). 



Paynter, E., Millar A. H., Welch, M., Baer-Imhoof, B., Coa, D., & Baer, B. Insights into the molecular basis of long-term storage and survival of sperm in the honeybee (Apis mellifera). Sci. Rep.,7: 40236.
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Dosselli, R., Grassl J., Carson, A., Simmons, L. W., & Baer, B. Flight behaviour of honey bee (Apis mellifera) workers is altered by early infections of the fungal parasite Nosema apis Sci. Rep., 6: 36649.
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Kurze, C., Dosselli, R., Grassl, J., Le Conte, Y., Kryger, P., Baer, B. & Moritz, R.Differential proteomics reveals novel insights into Nosema - honey bee interactions Insect Biochem. Mol. Biol., 79: 42-49.
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Liberti, J., Baer, B. & Boomsma, J. J. Queen reproductive tract secretions enhance sperm motility in ants Biol. Letters, 12: 20160722.
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Peng, Y., Grassl, J., Millar, A. H. & Baer, B. Seminal fluid of honey bees contains multiple mechanisms to combat infections of the sexually transmitted pathogen Nosema apis Proc. R. Soc. B, 283: 20151785.
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Grassl, J., Peng, Y., Baer-Imhoof, B., Welch, M., Millar, A. H., & Baer, B. Infections with the sexually transmitted pathogen Nosema apis trigger an immune response in the seminal fluid of honey bees (Apis mellifera) J. Prot. Res. available online. 
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Baer, B., Collins, J., Maalaps, K. & den Boer, S. P. A. Sperm use economy of honeybee (Apis mellifera) queens  Ecol. Evol., 6 (9): 2877-2885.
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Baer, B. & Millar, A.H. Proteomics in Evolutionary Ecology J. Prot. 135: 4-11. 
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Collins, J., Baer, B. & Weber, E.J. Evolutionary Biology in Economics: A Review The Economic Record, 92: 291–312.
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Baer, B. Proximate and ultimate consequences of polyandry in ants (Hymenoptera: Formicidae) Myrmecol. News 22: 1-9. 
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Peng, Y., Baer-Imhoof, B., Millar, A.H. & Baer, B. Consequences of Nosema apisinfection for male honey bees and their fertility Sci. Rep. 5: 10565. 
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Roberts, K., Evison, S., Baer, B. & Hughes, W.O.H. The cost of promiscuity: Sexual transmission of Nosema microsporidian parasites in polyandrous honey bees Sci. Rep. 5: 10982, 1-7. 
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Hoppe, P. P., Safer, A., Amaral-Rogers, V., Bonmatin, J. M., Goulson, D., Menzel, R., & Baer, B. Effects of a neonicotinoid pesticide on honey bee colonies: a response to the field study by Pilling et al. (2013) Environ. Sci. Eur. 27: 28. 
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Shaw, J., Boyd, A., House, M., Woodward, R., Mathes, F., Cowin, G., Saunders, M., & Baer, B. Magnetic particle mediated magnetoreception J. R. Soc. Interface, 12: 20150499. 
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Baer, B. Female Choice in Social Insects. In Peretti, A. & Aisenberg, A. eds.: Cryptic Female Choice in Arthropods: Patterns, Mechanisms and Prospects. Springer, pp 461-477.
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Collins, J., Baer, B. & Weber, E. J. Sexual selection, conspicuous consumption and economic growth J. Bioecon. 17: 189-206. 
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Lach, L., Kratz, M. & Baer, B. Parasitized honey bees are less likely to forage and carry less pollen J. Invertebr. Pathol. 130: 64-71. 
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den Boer, S.P.A., Stuerup, M., Boomsma, J.J. & Baer, B. The ejaculatory biology of leafcutter ants J. Insect Physiol. 74 : 56-62. 
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Baer, B. Sexual Selection in Social Insects. In Simmons, L.W.S. & Shuker, D. eds.: The Evolution of Insect Mating Systems. Oxford University Press, Oxford. pp 261-274.

Collins, J., Baer, B. & Weber, E. J. Economic growth and evolution: Parental preference for quality and quantity of offspring. Macroecon. Dynamics, 18 (8): 1773-1796. 
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Babis, M., Holman, L., Fenske, R., Thomas, M. & Baer, B. Cuticular lipids correlate with age and insemination status in queen honeybees Insect. Sociaux, 61 (4): 337-345. 
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Paynter, E., Baer-Imhoof, B., Linden, M., Lee-Pullen, T., Heel K., Rigby, P. & Baer, B. Flow cytometry as a rapid and reliable method to quantify sperm viability in the honeybee Apis mellifera Cytometry Part A 85 (5): 463-472. 
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Peng, Y., Pullen-Lee T., Heel, K., Millar, A.H. & Baer, B. Quantifying spore viability of the honey bee pathogen Nosema apis using flow cytometry. Cytometry Part A, 85(5) 454-462. 
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Stuerup, M., Baer, B. & Boomsma, J. J. Short independent lives and selection for maximal sperm survival make investment in immune defences unprofitable for leaf-cutting ant males  Behav. Ecol. Sociobiol. 68: 947-955. 
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Zareie, R., Eubel, H., Millar, A. H. & Baer, B. Long term survival of high quality sperm: Insights into the sperm proteome of the honeybee Apis mellifera. J. Prot. Res. 12(11): 5180-5188. 
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Stuerup, M., Baer-Imhoof, B., Nash, D. R., Boomsma, J. J. & Baer, B. When every sperm counts: factors affecting male fertility in the honeybee Apis mellifera, . Behav. Ecol. 24(5): 1192-1198. Download from Behavioral Ecology or Read abstract.

den Boer, S. P. A., Boomsma, J. J., & Baer, B. A technique to artificially inseminate leafcutter ants. Insect. Soc. 60: 111-118. 
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Chappell, P., Roberts, K., Baer, B. & Hughes, W. O. H. Mating system and population genetic structure of the bulldog ant Myrmecia pavida.. Myrmecol. News 18: 25-32.Download from Myrmecological News or Read abstract

Collins, J., Baer, B. & Weber, E. J. Population, technological progress and the evolution of innovative potential. University of Western Australia Discussion paper 13.21. Download from SSRN eLibrary or Read abstract


Jaffé, R., Garcia-Gonzalez, F., den Boer, S. P. A., Simmons, L. W. & Baer, B. Patterns of paternity skew among polyandrous social insects: What can they tell us about the potential for sexual selection? Evolution, 66 (12): 3778-3788.
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Baer, B., Zareie, R., Paynter, E., Poland, V. & Millar, A. H. Seminal fluid proteins differ in abundance between genetic lineages of honeybees. J. Prot. 75 (18): 5646-5653.Download from Journal of Proteomics or Read abstract.


Hartke, T. R. & Baer, B. The mating biology of termites: A comparative review. Anim. Behav. 82: 927-936.
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Lowe, E. C., Simmons, L. W., Baer, B. Worker heterozygosity and immune response in feral and managed honeybees (Apis mellifera). Aust. J. Zool. 59: 73-78.
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Fitzpatrick, J. L. & Baer, B. Polyandry reduces sperm length variation in social insects. Evolution 65: 3006-3012.
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King, M., Eubel, H., Millar, A. H. & Baer, B. Proteins within the seminal fluid are crucial to keep sperm viable in the honeybee Apis mellifera . J. Insect Physiol. 57: 409-414.Download from Journal of Insect Physiology or Read abstract

Poland, V., Eubel, H., King, M., Solheim, C., Millar, A. H., & Baer, B. Stored sperm differs from ejaculated sperm by proteome alterations associated with energy metabolism in the honeybee Apis mellifera. Mol. Ecol. 20:2643-2654.Download from Molecular Ecology or Read abstract

Baer B. The copulation biology of ants (Hymenoptera: Formicidae). Myrmecol. News 14: 55-68.
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Stuerup, M., den Boer, S. P. A., Nash, D. R., Boomsma, J. J., & Baer, B. Variation in male body size and reproductive allocation in the leafcutter ant Atta colombica: Estimating variance components and possible trade-offs. Insect. Soc. 58: 47-55.
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den Boer, S. P. A., Baer, B. & Boomsma, J. J. Seminal fluid mediates ejaculate competition in social insects. Science 327: 1506-1509.
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Armitage, S. A. O., Boomsma, J. J. & Baer, B. Diploid male production in a leaf-cutting ant. Ecol. Entomol. 35: 175-182.
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den Boer, S. P. A., Baer, B., Dreier, S., Aron, S., Nash, D. R. & Boomsma, J. J. Prudent sperm use by leaf-cutter ant queens. Proc. R. Soc. B 276: 3945-3953.
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Baer, B., Eubel, H., Taylor, N. L., O'Toole, N. & Millar, H. A. (2009) Insights into female sperm storage from the spermathecal fluid proteome of the honeybee Apis mellifera. Gen. Biol. 10: R 67.1 - 67.16.
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Baer, B., den Boer, S. P. A., Kronauer, D. J. C., Nash, D. R. & Boomsma, J. J. (2009) Fungus gardens of the leafcutter ant Atta colombica function as egg nurseries for the snake Leptodeira annulata. Insect. Soc. 56: 289-291.
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To see the electronic appendix click here

Himler, A. G., Calderal, E. J., Baer, B., Schultz, T., Fernandez-Marin, H. & Mueller U. G.(2009) No sex in fungus-farming ants or their crops. Proc. R. Soc. B 276: 2611-2616.
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Baer, B., Dijkstra, M., Nash, D. R., Mueller, U. & Boomsma, J. J. (2009) Sperm length evolution in the fungus-growing ants. Behav. Ecol. 20: 38-45.
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Baer, B., Heazlewood, J. L., Taylor, N. L., Eubel, H. & Millar, H. A. (2009) The seminal fluid proteome of the honeybee Apis mellifera. Proteomics 9: 2085-2097.
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Den Boer, S. P. A., Boomsma, J. J & Baer, B. (2009) Honeybee males and queens use glandular secretions to enhance sperm viability before and after storage. J. Insect Physiol. 55: 538-543.
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Den Boer, S. P. A., Boomsma, J.J & Baer, B. (2008) Seminal fluid enhances sperm viability in the leafcutter ant Atta colombica. Behav. Ecol. Sociobiol. 62: 1843-1849.
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Wilfert, L., Gadau, J., Baer, B., Reber, & Schmid-Hempel, P. (2007) Natural variation in the genetic architecture of a host-parasite interaction in the bumblebee Bombus terrestris. Mol. Ecol. 16: 1327-1339.
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Baer, B., Armitage, S. A. O. & Boomsma, J. J. (2006) Sperm storage induces an immunity cost in ants. Nature 441: 872-875.
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Baer, B., de Jong, G., Schmid-Hempel, R., Schmid-Hempel, P., Høeg, J. T. & Boomsma, J. J. (2006) Heritability of sperm length in the bumblebee Bombus terrestris. Genetica 127: 11-23.
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Baer, B. & Boomsma, J. J. (2006) Mating biology of the leaf-cutting ants Atta colombicaand A. cephalotes. J. Morph. 267: 1165-1171.
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Baer, B. & Schmid-Hempel, P. (2006) Phenotypic variation in male and worker encapsulation response in the bumblebee Bombus terrestris. Ecol. Entomol. 31: 591-596.
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Boomsma J. J., Baer B. & Heinze J. (2005): The evolution of male traits in social insects. Annu. Rev. Entomol. 50: 395-420.
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Baer, B. & Schmid-Hempel, P. (2005) Sperm influences female hibernation success, survival and fitness in the bumblebee Bombus terrestris. Proc. R. Soc. L. 272 (1560): 319-323.
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Baer, B. (2005) Sexual selection in Apis bees. Apidologie 36 (2), 187-200.
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Brown, M. J. F. & Baer, B. (2005) The evolutionary significance of long copulation duration in bumblebees. Apidologie 36 (2): 157-167.
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Baer B., Krug A., Boomsma J. J. & Hughes W. O. H. (2005) Examination of the immune responses of males and workers of the leaf-cutting ant Acromyrmex echinatior and the effect of infection. Insect. Soc. 52 (3): 298-303.
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Baer B. & Boomsma J. J. (2004): Male reproductive investment and polyandry in fungus-growing ants. Behav. Ecol. 15 (3): 426-432.
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Baer, B. (2003): Bumblebees as model organisms to study male sexual selection in social insects. Behav. Ecol. Sociobiol. 54 (6): 521-533.
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Baer B. & Schmid-Hempel P. (2003): Effects of selective episodes in the field on life history traits in the bumblebee Bombus terrestris. Oikos 101 (3): 563-568.
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Baer, B., Schmid-Hempel, P., Høeg J. T. & Boomsma, J. J. (2003): Sperm length, sperm storage and mating system evolution in bumblebees. Insect. Soc. 50 (2): 101-108.
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Baer B. & Schmid-Hempel P. (2003): Bumblebee workers from different sire groups vary in susceptibility to parasite infections. Ecol. Letters 6 (2): 106-110.
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Brown M. J. F., Baer B., Schmid-Hempel R. & Schmid-Hempel P. (2002): Dynamics of multiple mating in the bumblebee Bombus hypnorum. Insect. Soc. 49 (4): 315 319.
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Baer B. & Schmid-Hempel P. (2001): Unexpected consequences of polyandry for parasitism and fitness in the bumblebee B. terrestris. Evolution 55 (8): 1639-1643.
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Sauter A., Brown M. J. F., Baer B. & Schmid-Hempel P. (2001): Males of social insects can prevent queens from multiple mating. Proc. R. Soc. L., 268 (1475): 1449-1454.
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Baer B., Morgan E. D. & Schmid-Hempel P. (2001): A non-specific fatty acid prevents females from re-mating in bumblebees. Proc. Natl. Acad. Sci. 98 (7): 3926-3928.
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Baer B., Maile R., Schmid-Hempel P. Morgan E. D. & Jones G. R. (2000): Chemistry of a mating plug in bumblebees. J. Chem. Ecol. 26 (8): 1869-1875.
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Baer B. & Schmid-Hempel P. (2000): Applied aspects of the artificial insemination for bumblebees. In Sommeijer, M J. & de Ruijter, A. eds: Insect pollination in greenhouses. Koninklijke Bibliotheek, Den Haag.

Baer B. & Schmid-Hempel P. (2000): The artificial insemination of bumblebees. Insect. Soc. 47 (2): 183-187.
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Duvoisin N., Baer B. & Schmid-Hempel P. (1999): Sperm transfer and male competition in a bumblebee. Anim. Behav. 5 (4): 743-749.
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Baer B. & Schmid-Hempel P. (1999): Experimental variation in polyandry affects parasite loads and fitness in a bumblebee. Nature 397 (6715): 151-154.
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Brodmann P. A., Reyer H. U. & Baer B. (1997): The relative importance of habitat structure and of prey characteristics for the foraging success of water pipits (Anthus spinoletta). Ethology 103 (3): 222-235.
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