Gregory S. Gilbert Research Group

Environmental Studies Department, University of California Santa Cruz

Abbreviated Curriculum Vitae
Yuri P. Springer, Ph.D.

Current Position
Disease Ecologist, National Ecological Observatory Network, (neon), Boulder, CO

Education
University of Otago, New Zealand (Postdoctoral Fellow, 2008-2009)
University of California Santa Cruz (Ph.D. Ecology & Evolutionary Biology, 2006)
University of California Los Angeles (B.S. Biology with emphasis in Marine Biology, 1994

Research Interests
Biogeography and spatial structure of species interactions
Epidemiology of chronic and infectious diseases
Ecological and evolutionary roles of parasites in natural ecosystems
Population and community ecology in marine ecosystems

Honors
Summa cum laude honors, 1997
Phi Beta Kappa honors society, 1997
Highest Honors, UCLA biology department, 1997
Honors, UCLA College of Letters and Sciences, 1997
Undergraduate research award, UCLA biology department, 1997
UCLA honors program, 1992-1997

Select Recent Publications
Springer, Y.P., Hardcastle, B.H., and G.S. Gilbert. 2007. Soil calcium and plant disease in serpentine ecosystems: a
      test of the pathogen refuge hypothesis. Oecologia, 151(1): 10-21 pdf
Springer, Y.P., 2007. Clinal resistance structure and pathogen local adaptation in a serpentine flax/flax rust interaction.
      Evolution, 61(8): 1812-1822 pdf
Springer, Y.P., 2009. Edaphic quality and plant/pathogen interactions: effects of soil calcium on fungal infection of a
      serpentine flax. Ecology, 90(7): 1852-1862 pdf
Springer, Y.P., Koehler, A.V, and R Poulin. 2009. Isolation and characterization of 27 polymorphic microsatellite loci
      for Maritrema novaezealandensis, a marine trematode from New Zealand. Molecular Ecology Resources, 9: 1375-1379
Springer, Y.P., Do extreme environments provide a refuge from pathogens? A phylogenetic test using serpentine flax.
      American Journal of Botany, 96(11): 2010-2021 pdf
Springer, Y.P., Hays, C.G, Carr, M.H, and M.R. Mackey. Towards ecosystem-based management of marine macroalgae:
      the bull kelp, Nereocystis luetkeana. Oceanography and Marine Biology: An Annual Review (in press)
Springer, Y.P., Samuel, M.C., and G. Bolan. Socioeconomic gradients in STD infection: a geographic information system
      (GIS)-based analysis of poverty, race/ethnicity, and Gonorrhea rates in California between 2004 and 2006.
      American Journal of Public Health (in press)

Select work experience
Postdoctoral fellow, Zoology dept., University of Otago, New Zealand (Mar 2008-June 2009)
   Experimental studies testing genetic and morphological constraints on host specificity of parasites
Research Associate, STD epidemiology/surveillance branch, California Department of Public Health (June 2007-~present)
   GIS-based analyses of racial and socioeconomic gradients in Gonorrhea rates across California
Research fellow, University of California Santa Cruz (June 2006-June 2007)
   Ecology and potential impacts of harvesting of marine algae on coastal marine ecosystems

Select teaching experience
Assistant Instructor, UCSC, Departments of Biology and Environmental Studies, 1998-2006 Courses taught: General Principles of Biology, Introduction to Cellular/Molecular Biology, Introduction to Physiological/Development Biology, Introduction to Ecology/Evolutionary Biology, Evolution, Behavioral Ecology, Marine Ecology, General Ecology, Kelp Forest Ecology, Field Methods in Marine Ecology, Marine Conservation, Animal Physiology, Plant Pathology, Principles of the Physical and Chemical Environment, and Invertebrate Zoology (at UCLA, 1996)
Biology tutor, Georgiana Bruce Kirby College Preparatory School, 2006

Leadership
Graduate Student Representative, UCSC Biology Department, 2002-2004 Elected delegate representing graduate students at meetings of departmental faculty and the university-wide graduate student association

Expanded Research Interests. My dissertation project was motivated by a strong interest in the patterns, causes, and implications of spatial variation in host/pathogen interactions. In a biogeographic sense, hosts are distributed among multiple, spatially discrete populations across the species’ range. The frequency and intensity of interactions with a particular pathogen species may vary considerably among these populations. Within particular populations, host/pathogen interactions may be modulated by any number of biotic and abiotic factors. The resulting spatial variation in the frequency, intensity, and/or outcome of interactions between hosts and pathogens should further produce geographic heterogeneity in their coevolution. In particular, traits that underlie host resistance and pathogen virulence should be under different selection pressure in different interacting populations, and this may generate predictable patterns in coevolved traits. My work focuses on characterizing patterns of spatial variation in the frequency and intensity of host/pathogen interactions, identifying the ecological mechanisms that underlie this variation, and exploring the resulting impacts on geographic patterns of coevolution.

Many pathogens are able to infect more than one host species, and I am also interested in phylogenetic variation in host/pathogen interactions. Why are some pathogen host specialists while others are more general? For the generalists, what factors determine which host species they can attack, and how does pathogen virulence vary among these hosts? What biotic and/or abiotic factors promote host switching and changes in host range breadth? To investigate these questions I attempt to explicitly incorporate phylogenetic characteristics in my studies of host/pathogen interactions.

Study System: My dissertation focused on interactions between 13 species of wild flax in the genus Hesperolinon and their common fungal pathogen, the rust Melampsora lini. All of the host species grow on serpentine soils, which are known for their many unique and biotically stressful edaphic properties: coarse rocky texture with low water-holding potential, high concentrations of magnesium, iron, silica, and various heavy metals, and extreme deficiencies in nutritive elements including calcium, nitrogen, phosphorus, and potassium. Calcium deficiencies seem to be particularly important for serpentine plant ecology, and evidence from the literature of calcium’s important roles in various plant immune responses further suggests that low calcium levels should have important consequences for interactions with pathogens.

Helen Sharsmith, who wrote the original monograph for the genus in 1961 conducted extensive observational studies of all 13 Hesperolinon species and concluded that some are serpentine specialists (i.e., only found on extreme, low calcium serpentine soils) while others are generalists with broader edaphic tolerances that grow on soils with a range of serpentine influence. I hypothesized that the low calcium content of serpentine soils should create conditions that strongly influence host susceptibility and the consequences of infection for associated plants. Specifically, host populations or species associated with low calcium soils should experience more frequent and/or severe infection. Because of variation in edaphic associations in the genus Hesperolinon, both among populations of soil generalists and among species, this system is an ideal one in which to test for spatial and phylogenetic variation in host/pathogen interactions.

Chapter 1: Working with Bree Hardcastle, an undergraduate senior thesis student, I conducted a greenhouse inoculation experiment to test for the effect of serpentine soil calcium levels on pathogen infection. We experimentally manipulated the calcium concentration in field-collected serpentine soils, inoculated flax plants growing in these soils with fungal spores, and recorded levels of disease. We used the edaphic generalist H. californicum as the host species. Results demonstrated a significant negative relationship between disease prevalence (the percentage of hosts in a particular soil treatment showing disease symptoms) and soil calcium concentrations.

Springer, Y. P., B. A. Hardcastle, and G. S. Gilbert. 2007. Soil calcium and plant disease in serpentine ecosystems: a test of the pathogen refuge hypothesis. Oecologia 151(1):10-21. (link to article PDF)

Chapter 2: To see whether this mechanism influenced patterns of infection in the field I conducted a 4-year epidemiological study of M. lini infection of H. californicum. I collected data on infection prevalence and severity during annual surveys in 16 populations spanning the host’s biogeographic range, and I also analyzed soil samples from each site. Results confirmed that plants growing in low calcium soils were associated with higher levels of disease prevalence and severity. Studies of the fitness effects of disease revealed that rust infection caused significant reductions in host survival and fecundity, and there was evidence of a demographic feedback between infection prevalence and host density across survey years. Epidemiological surveys identified a latitudinal cline in disease: the prevalence and severity of symptoms was high in northern host populations and decreased gradually and continuously towards the south.

Springer, Y. P. 2009. Edaphic quality and plant-pathogen interactions: Effects of soil calcium on fungal infection of a serpentine flax. Ecology 90(7):1852-1862. (link to article PDF)

Chapter 3: I conducted a greenhouse inoculation experiment to investigate whether this clinal pattern of disease was reflected in the distribution of rust resistance genes among host populations. To characterize host resistance structure, I inoculated multiple maternal lines from each of the 16 H. californicum study populations with 10 samples of rust, each collected from a different host population. Results elucidated a clinal pattern in resistance structure: levels of genetic resistance were very low in northern host populations and increased towards the south. Analyses of cross-inoculation data further revealed some interesting patterns of local adaptation of the pathogen.

Springer, Y. P. 2007. Clinal resistance structure and pathogen local adaptation in a serpentine flax-flax rust interaction. Evolution 61(8):1812-1822. (link to article PDF)

Chapter 4: Through DNA sequencing analyses I constructed a phylogeny of the host genus. In parallel with the epidemiological surveys conducted for H. californium I collected three years of infection data in at least five populations of each of the remaining 12 Hesperolinon species. I also collected and analyzed soil samples from each of these locations. Using phylogenetically independent contrast analyses I then compared the soil/disease relationship across the entire host genus. Surprisingly, these results were opposite of those for H. californicum: host populations growing on more extreme serpentine soils were associated with lower levels of disease prevalence and severity. This result supported a “pathogen refuge effect” hypothesis by suggesting that abiotically extreme environments may be associated with reductions in the frequency and/or intensity of antagonistic species interactions. As part of related analyses I also performed ancestral-state reconstruction using soil data to investigate evolutionary patterns associated with plant specialization on extreme serpentine soils.

Springer, Y. P. 2009. Do extreme environments provide a refuge from pathogens? A phylogenetic test using serpentine flax. American Journal of Botany 96(11):2010-2021. (link to article PDF)

I have quite a few tissue samples (extracted DNA) and a fairly sizable seed collection left over from my thesis. If you are interested in using them for studies involving Hesperolinon, or if you’d like to collaborate with me on research involving these or other plants, please drop me an email: yurispringer@gmail.com.