• Linking within-host and between-host processes to better understand the ecology and evolution of

    host-microbe interactions





    Jessica L. Hite

    PoE Postdoctoral Fellow

    Cressler Lab

    University of Nebraska



  • Hosts can employ numerous mechanisms to defend themselves against pathogens — this arsenal ranges from behavioral changes to cultivating beneficial microbes. Each of these defenses interacts through direct and indirect pathways and carry cost-benefit tradeoffs depending on the genetic, nutritional, and environmental conditions that govern the host's physiology, exposure to pathogens, and susceptibility to disease. These host-pathogen interactions carry substantial ecological and evolutionary consequences.


    My research focuses on understanding: (1) the physiological underpinnings of host defense, (2) the subsequent life-history trade-offs for both hosts and pathogens, and (3) how these individual-level processes scale-up to drive population-level outcomes (e.g., host population stability, the evolution of pathogen virulence). I address these questions using invertebrates as models.


    The production, development, and clearance of parasites within individual hosts fundamentally shapes the transmission and spread of parasites among hosts. These cross-scale dynamics modulate the ecology and evolution of host-parasite interactions — with implications for public health concerns such as how current biomedical practices influence directly or indirectly affect host defenses and pathogen evolution, the use of nutrition-driven approaches to combat disease ('immunonutrition'), and managing wildlife diseases. In addition to advancing our ability to understand and managing infectious disease, accounting for these cross-scale feedbacks also provides crucial insight into the role of parasites in natural food webs.


    To date, most empirical studies tend to focus on a single scale:

    the production or clearance of parasites within hosts or the transmission of parasites between hosts.

    My work focuses on developing novel approaches (empirical and theoretical) to integrate across these different scales of biological organization. Host nutrition drives both within-host and between host processes. While resources form the cornerstone to ecological questions, they have been largely overlooked in epidemiological studies (especially theory). Understanding how these resource-driven feedbacks (at both the individual and population level) shape the life history traits of both hosts and parasites is a major focus of my research.


    This endeavor also allows me to address key ecological questions such as:

    •  How does the individual-level variation in key traits of hosts (e.g., size, stage, sex, genotype) modulate variation in exposure, susceptibility, and transmission of parasites? 
    •  How does this intraspecific variation scale up to drive population-level dynamics (e.g., the demographic structure and stability of host populations; the invasion, spread, and severity of disease)?
    • How do parasites shape the dynamics and stability of their host populations?
    • How do host population dynamics shape parasite plasticity and evolution?


    By merging two, currently separate bodies of work (consumer-resource and epidemiology), my work illustrates that classical models often miss crucial components of host-parasite interactions because they overlook intraspecific variation.


    My approach combines experiments (individual to population level), field surveys, & mathematical models in a few different host-parasite systems and carries implications for both basic and applied biology.


  • Research

    Motivating questions:

    (1) How do links between individual-level variation (e.g., size, stage, genotypic, gut microbiota) and parasites influence:

    • The structure and dynamics of natural populations
    • Host-parasite interactions
    • Parasite evolution

    (2) How does environmental variation (e.g., UVR, resources) alter these interactions and their population-level consequences


    General Approach:

    I use theory as a guide to understand patterns and processes in natural systems.


    My work combines theory from several different fields:

    • consumer-resource 
    • epidemiology
    • stage structure
    • sex-ratio
    • adaptive dynamics
    • life-history

    This mix of theory helps to disentangle results that often arise through complex feedbacks and multiple indirect effects.



    Jaime Bosch (CSIC, Spain) - Identifying multiple pathways that drive Amphibian chytrid dynamics


    Kristi Montooth (UNL) - host (Drosophila) nutrition, physiology, and parasite evolution


    Justin Buchanan (UNL) - host (Drosophila) nutrition, physiology, and parasite evolution


    John DeLong (UNL) - Gillespie Evolutionary Models (GEM), host diversity, and pathogen evolution


    Paul Orlando (IU) - Stage-structured interactions

  • Research Projects

    Parasites shape the demography and stability of host populations.

    What do the stage structure and stability of host populations have in common? both are parasite-mediated


    Synopsis: Across multi-year, multi-lake field surveys and multiple in situ mesocosm experiments where we created experimental epidemics, we show that during epidemics of a virulent fungal parasite (Metschnikowia bicuspidata):


    1) host populations become more juvenile dominated

    (this decreases overall biomass of a key consumer/resource in aquatic ecosystems and may even increase the host's risk of extinction)


    2) Destabilizes host populations by shifting juvenile and adult hosts into more synchronized cycles (which increases overall population variation).

    Parasites & Host allocation to sex

    How do parasites influence host allocation to sex?


    Synopsis: Across a multi-year, multi-lake field survey and a field-deployed mesocosm experiment, we found that a zooplankton host (Daphnia dentifera) appears to increase allocation to sex during fungal epidemics. We then tested two mechanistic drivers of this pattern. Specifically, we evaluated whether: (1) infection-stressed hosts allocate more to sexual reproduction or (2) apparent changes in sex resulted because males resist infection and become overrepresented during epidemics.


    We used a combination of field patterns, experiments, and model of infection risk (parameterized with experimental data), to arbitrate our two mechanistic hypotheses. We found no support for the resistance hypothesis; males were not more resistant, hence likely did not escape culling by parasites. Instead, we found that individual female hosts increased allocation to sex when infected. Together, these results advance understanding of the mechanisms driving variation in allocation to sex across natural populations.

    Direct & indirect drivers of disease

    Using a combination of multi-year field surveys and in situ experiments, my collaborators and I asked:


    How do habitat, predators of parasites, host stage structure, and host diversity jointly drive epidemics of the devastating amphibian chytrid fungus?

    Parasite evolution, host resources, and population stability

    Synopsis: Clay Cressler and I are investigating how host resources and influence host population dynamics and in turn, how these processes modulate the evolution of parasite life history traits (e.g., virulence).


    To address these questions, we began by integrating an energetic model of disease to identify evolutionarily stable strategies (ESS) using an adaptive dynamics approach.


    Our results illustrate that during stable limit cycles, feedbacks between host resources and immune function become particularly important. These feedbacks can lead to the emergence of evolutionary bistability where parasites can evolve a high virulence strategy that strongly stabilizes the host population or a low virulence strategy, that only weakly stabilizes.


    Theory typically predicts that parasites should stabilize their host populations, so we were surprised to find the low virulence ESS. It turns out, that this strategy allows the parasite to 'ride the cycles' of their host populations and maintain epidemics during periods of low host population density.


    We are currently working on experiments to test these predictions.


  • Publications

    Hite J.L. and C.E. Cressler. Resource-driven changes to host population stability alter the evolution of virulence and transmission. 2018. Philosophical Transactions of the Royal Society, B.



    Strauss, A.T., J.L. Hite, M.S. Shocket, M.A. Duffy, C.E. Cáceres, and S.R. Hall. Rapid evolution rescues hosts from competition and disease and – despite a dilution effect – increases the density of infected hosts. 2018. Proc. Roy. Soc. London B.



    Shocket, M.S., A.T. Strauss, J.L. Hite, M. Šljivar, D.J. Civitello, M.A. Duffy, C.E. Cáceres, and S.R. Hall. Temperature drives epidemics in a zooplankton-fungus disease system: A trait-driven approach points to transmission via host foraging. 2018 American Naturalist 191(4).



    Hite J.L. R. M. Penczykowski, M. S. Shocket, K. Griebel*, A.T. Strauss, M. A. Duffy, C. E. Cáceres, and S.R. Hall. 2017. Allocation, not male resistance, increases male frequency during epidemics: a case study in facultatively-sexual hosts. Ecology. 98(11), 2773-2783. http://onlinelibrary.wiley.com/doi/10.1002/ecy.1976/full


    Hite, J.L., S. Fernández-Beaskoetxea, D.C. Medina, J. Bosch, and S.R. Hall. 2016. Joint effects of habitat, predators, host stage structure, and diversity on amphibian chytrid. Proc. Roy. Soc. London B. 283. http://rspb.royalsocietypublishing.org/content/283/1835/20160832


    Hite, J.L., R.M. Penczykowski, M.A Shocket, A.T. Strauss, P. A. Orlando, M.A. Duffy, C.E. Cáceres, and S.R. Hall. 2016. Parasites destabilize host populations by shifting stage-structured interaction. Ecology 97(2): 439-449.



    Strauss A.T., M.S. Shocket, D.J. Civitello, J.L. Hite, R.M. Penczykowski, M.A. Duffy, C.E. Cáceres, and S.R. Hall. 2016. Habitat, predators, and hosts regulate disease in Daphnia through direct and indirect pathways. Ecological Monographs. 86(4), 393-411. http://onlinelibrary.wiley.com/doi/10.1002/ecm.1222/full


    Civitello, D.J., J.L. Hite, and S.R. Hall. 2014. Potassium enrichment stimulates the growth and reproduction of Daphnia. Oecologia 175: 773-780. https://link.springer.com/article/10.1007/s00442-014-2943-5


    Wojdak J. M., J. C. Touchon, J. L. Hite, B. Meyer*, and J. R. Vonesh. 2014. Consequences of induced hatching plasticity depend on predator community. Oecologia 175: 1267-1276.


    Civitello, D.J., R.M. Penczykowski, J.L. Hite, M.A. Duffy, and S.R. Hall. 2013. Potassium stimulates fungal epidemics in a freshwater invertebrate. Ecology 94: 380-388.


    Hite, J.L., C.A. Rodríguez Gómez, S.C. Larimer, A.M. Díaz–Lameiro, and R. Powell. 2008. Population densities and structural habitat use of St. Vincentian Anoles. The Caribbean Journal of Science 44: 102-115.


    In the works (full manuscripts in review/revision, available upon request)

    Hite. J.L., M. C. Hughey, K.M. Warkentin, and J.R. Vonesh. Cross-ecosystem effects of terrestrial predators link tree frogs, zooplankton, and aquatic primary production. In review.


    Shocket, M. S., D., Vergara, A. Sickbert, J. Walsman, A.T., Strauss, J.L. Hite, M.A., Duffy, C.E., Cáceres, S.R., Hall. Parasite rearing and infection temperatures jointly influence disease transmission and shape seasonality of epidemics. Accepted: Ecology


    Hite J.L., R. M. Penczykowski, D. J. Civitello, M. S. Shocket, A. T. Strauss, M. A. Duffy, C. E. Cáceres, and S. R. Hall. Parasites shift stage structure of hosts towards more juveniles in a planktonic disease system. In revision


    Orlando, P.A., Hite. J.L., and Spencer R. Hall. Disease as a cause of cohort cycles: theory for disease in a physiologically structured host population. In revision


    Orlando, P.A., Hite. J.L., and Spencer R. Hall. Stage structure increases opportunities for fluctuation-dependent coexistence. In revision


  • Outreach: Combining Art & Science

    Outreach is an essential component that strongly informs my approach to teaching and research (and vice versa).


    Since 2014, I have been working with the local Audubon Chapter (Sassafras Audubon Society) where I helped develop a conservation and outreach program 'Swifts in the City' — a collaborative project focused on improving the plight of the chimney swift (a "near-threatened" bird species).


    Chimney swift ('the dolphins of the sky') populations appear to be declining quite drastically (i.e., IUCN “near threatened” in the US, COSEWIC “federally threatened” in Canada). While the causes of these declines are multifaceted, a major issue is the loss of breeding habitat (old hollow tree snags, and industrial and residential chimneys).


    Through collaborations involving numerous community partners (e.g., local and national Audubon Chapters, community artists, schools, WonderLab museum of science, health, and technology, and numerous funding agencies), we designed, built, and installed eight new breeding habitats "functional sculptures" that mimic freestanding chimneys. We also led numerous outreach projects to:


    (1) provide additional breeding and roosting habitat for this endangered bird.

    (2) increase awareness and appreciation of this amazing bird and their role in the global food web by combining art and science


    For more information on chimney swifts or this project, please visit our website:

    Swifts in the City



    Pop-up card from an art-science class on 'City Birds' at Harmony School

  • Teaching

    I have been fortunate to teach a variety of classes and mentor several outstanding undergraduate students. These experiences have helped me refine my teaching and mentoring practices.



    Three unifying principles guide my teaching and mentoring approach:

    (1) combining foundational principles with practical application

    (2) guided active learning

    (3) quantitative reasoning



    I believe this approach helps to ensure a higher level of understanding, critical thinking, empowerment, enthusiasm for learning, and student engagement.


    I connect lessons in the classroom to real-world current issues. This approach helps simplify abstract ideas and make them more tangible and applicable for students.


    In both the classroom in the lab, I cultivate a supportive interactive environment where students not only become comfortable asking questions but also help each other discover answers and ways to address open questions.



  • Curriculum Vitae

  • Contact Info.

    University of Nebraska

    School of Biological Sciences

    Cressler Lab

    Manter Hall 402

    Lincoln, NE 68588-0118

    Phone: 402.472.2720

    Email: jhite2@unl.edu