Biology

Evolutionary Ecology, Population Genetics, and Conservation of Amphibians.

Research in my lab uses field and laboratory experimentation in conjunction with molecular genetic tools to understand local adaptation, speciation, and gene flow using amphibian species as models. Current projects include analyses of tiger salamander (Ambystoma tigrinum) hybrid zones using single nucleotide polymorphisms (SNPs), and landscape genetics of several California amphibian species (Ambystoma californiense, Bufo boreas, Pseudacris regilla, Rana aurora, and Taricha torosa) using microsatellites. Our goal is to provide empirical data that are relevant to the conservation and management of amphibian populations while simultaneously improving our understanding of evolution and ecology in general.

Postdoc:  Evolution and Ecology, UC Davis

Ph.D. 2005 Evolution and Ecology, University of Missouri

B.S. 1999 Ecology, Ethology, and Evolution, University of Illinois

Johnson, J. R., M. E. Ryan, S. J. Micheletti, and H. B. Shaffer.  2013.  Short pond hydroperiod decreases fitness of non-indigenous hybrid salamanders.  Animal Conservation.  DOI:  10:1111/acv.12029.

Ryan, M. E., J. R. Johnson, B. M. Fitzpatrick, L. J. Lowenstein, A. M. Picco, and H. B. Shaffer.  2013. Agricultural landscape in California favor introduced hybrid tiger salamanders.  Conservation Biology 27: 95102.

Wang, I. J., J. R. Johnson, B. B. Johnson, and H. B. Shaffer. 2011. Effective population size is strongly correlated with breeding pond size in the endangered California tiger salamander, Ambystoma californiense. Conservation Genetics 12:911-920.

Johnson, J. R., R. C. Thomson, S. J. Micheletti*, and H. B. Shaffer. 2011. The origin of tiger salamander (Ambystoma tigrinum) populations in California, Oregon, and Nevada: introductions or relicts? Conservation Genetics 12:355-370.

Johnson, J. R., B. B. Johnson, and H. B. Shaffer. 2010. Genotype and temperature affect locomotor performance in a tiger salamander hybrid swarm. Functional Ecology. 24:1073-1080.

Johnson, J. R., B. M. Fitzpatrick, and H. B. Shaffer. 2010. Admixture dynamics of tiger salamanders: Fitness of early-generation hybrids and the retention of low-fitness genotypes in contemporary populations. BMC Evolutionary Biology 10:147.

Fitzpatrick, B. M., J. R. Johnson, D. K. Kump, J. J. Smith, S. R. Voss, and H. B. Shaffer. 2010. Rapid spread of invasive genes into a threatened native species. PNAS 107:3606-3610.

Thomson, R. C., I. J. Wang, and J. R. Johnson. 2010. Invited Review: Genome-enabled molecular marker development for ecology, evolution, and conservation. Molecular Ecology 19:2184–2195.

Fitzpatrick, B. M., J. R. Johnson, D. K. Kump, H. B. Shaffer, J. J. Smith, and S. R. Voss. 2009. Rapid xation of non-native alleles revealed by genome-wide SNP analysis of hybrid tiger salamanders. BMC Evolutionary Biology 9:176.

Ryan, M. E., J. R. Johnson, and B. M. Fitzpatrick. 2009. Ecological consequences of introduced genes: Invasive tiger salamander genotypes impact native amphibians. PNAS 106:11166-11171.