Bradley R. Anholt

Director, BMSC
Professor, University of Victoria

Research Interests:
Population and community consequences of antipredator defenses in ciliated protozoans.

Ecology and evolution of sex ratios in a marine copepod.

My research focuses on how adaptive changes in behaviour affect other members of a food-web through their indirect connections.

I have worked extensively on amphibian larvae and their predators in southern Michigan and on hybridogenic frogs in Europe. The work has demonstrated strong inter-dependencies between the availability of resources and mortality-risk for individuals and that changes in behaviour can alter the competitive regime.

The complex life histories of amphibians preclude a complete study of their population dynamics. So, I have established a model protozoan system to test the rapidly developing theories of the population and community dynamic consequences of induced anti-predator defenses.

In addition we have been investigating the evolution and ecology of biased sex ratios in the marine copepod Tigriopus californicus. This variation is heritable, and has an environmental component as well.


Phone: 250-728-3301 ext. 215


Department of Biology, University of Calgary, Calgary, AB, Canada


Current Research: Evolution of biased sex ratios in Tigriopus californicus.
Principal Ivenstigator: Dr. Brad Anholt, BMSC, University of Victoria.

The harpacticoid copepod, Tigriopus californicus inhabits high intertidal splash pools along the west coast of North America from Baja California to Alaska. Although its habitat provides refuge from a diverse predator fauna, the high intertidal pools are characterized by extreme fluctuations in temperature and salinity. Clutch sex ratios (proportion of males in a brood) from natural populations of T. californicus often deviate from the binomial distribution. We have been accumulating corroborative evidence in support of the hypothesis of a polygenic sex determination mechanism. Under this model, variation in sex ratio is a consequence of an underlying trait, the value of which is determined by the additive effect of many alleles at multiple loci.

Alexander, H.J., Richarson, J.M.L., Edmands, S., and B.R. Anholt. 2015. Sex without sex chromosomes; genetic architecture of multiple loci independently segregating to determine sex ratios in the copepod Tigriopus californicus. J. Evol. Biol. 2015 Dec; 28(12): 2196-207.

Alexander, H.J., Richardson, J.M.L. and Anholt, B.R. 2014. Multi-generational response to artificial selection for biased clutch sex ratios in Tigriopus californicus populations. J Evol Biol. 27 (9): 1921-1929.

Bateman, A. W., Vos, M. and Anholt, B. R. 2014. When to defend: Antipredator defenses and the predation sequence. American Naturalist, 183(6): 847-855.

Fisher, J. T., Pasztor, C., Wilson, A., Volpe, J. P., and Anholt, B. R. 2014. Recolonizing sea otters spatially segregate from pinnipeds on the Canadian Pacific coastline: The implications of segregation for species conservation. Biological Conservation, 177: 148–155.

Richardson, J. M. L., Govindarajulu, P., and Anholt, B. R. 2014. Distribution of the disease pathogen Batrachochytrium dendrobatidis in non-epidemic amphibian communities of western Canada. Ecography, 37(9): 883-893.

Fisher, J. T., Anholt, B. R., Bradbury, S., Wheatley, M. and Volpe, J. P. 2013 Spatial segregation of sympatric marten and fishers: the influence of landscapes and species-scapes. Ecography, 36(2): 240-248.

Fisher, J. T., Bradbury, S., Anholt, B. R., Nolan, L., Roy, L., Volpe, J. P. and Wheatley, M. 2013. Wolverines (Gulo gulo luscus) on the Rocky Mountain slopes: natural heterogeneity and landscape alteration as predictors of distribution. Canadian Journal of Zoology-Revue Canadienne De Zoologie, 91(10): 706-716.

Hamilton, P. T., Richardson, J. M. L., and Anholt, B. R. 2012. Daphnia in tadpole mesocosms: trophic links and interactions with Batrachochytrium dendrobatidis. Freshwater Biology, 57(4): 676–683.

Hamilton, P. T., Richardson, J. M. L., Govindarajulu, P., and Anholt, B. R. 2012. Higher temperature variability increases the impact of Batrachochytrium dendrobatidis and shifts interspecific interactions in tadpole mesocosms. Ecology and Evolution, 2(10): 2450-2459.

Kratina, P., LeCraw, R. M., Ingram, T., and Anholt, B. R. 2012. Stability and persistence of food webs with omnivory: Is there a general pattern?. Ecosphere, 3(6).

Fisher, J. T., Anholt, B. R. and Volpe, J. P.  2011. Body mass explains characteristic scales of habitat selection in terrestrial mammals. Ecology and Evolution, 1(4).

Kratina, P., Hammill, E., and Anholt, B. R. 2010. Stronger inducible defences enhance persistence of intraguild prey. Journal of Animal Ecology, 79(5): 993–999.

Hammill, E., Petchey, O. L., and Anholt, B. R. 2010. Predator functional response changed by induced defenses in prey. American Naturalist, 176(6): 723-731.

Hammill, E., Kratina, P., Beckerman, A. P., and Anholt, B. R. 2010. Precise time interactions between behavioural and morphological defences. Oikos, 119(3): 494-499.

Voordouw, M. J.; Anholt, B. R.; Taylor, P. J.; and Hurd, H. 2009. Rodent malaria-resistant strains of the mosquito, Anopheles gambiae, have slower population growth than -susceptible strains. Bmc Evolutionary Biology, 9: 76.

Voordouw, M. J., Stebbins, G., Robinson, H. E., Perrot-Minnot, M., Rigaud, T., and Anholt, B. R. 2008. Genetic variation in the primary sex ratio in populations of the intertidal copepod, Tigriopus californicus, is widespread on Vancouver Island. Evolutionary Ecology Research, 10(7): 1007-1023.

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