(1) How do links between individual-level variation (e.g., size, stage, genotypic, reproductive mode) and parasites influence:
(2) How environmental variation (e.g., UVR, resources) alters these interactions and their population-level consequences
I find that using theory as a guide can provide a powerful foundation for understanding patterns and processes in natural systems. This exciting challenge motivates much of my research.
My work typically combines theory from several different fields:
This mix of theory helps to disentangle results that often arise through complex feedbacks and indirect effects.
Currently, I am working with Clay Cressler to use adaptive dynamics to understand how feedbacks between host resources and stage structure influence host populations dynamics and parasite evolution.
Parasites & Host population Stage Structure
What do the stage structure and stability of host populations have in common? They are both 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.
This paper is in press at Ecology
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 stability
Synopsis: We are currently investigating how host resources and stage structure influence host population dynamics and in turn, how these processes modulate the evolution of parasite life history traits.
We are using a combination of modeling and experimental evolution approaches. More coming soon!
Hite J.L. and C.E. Cressler. Resource-driven changes to host population stability alter the evolution of virulence and transmission. In press. Philosophical Transactions of the Royal Society, B.
Hite J.L., R. M. Penczykowski, M. S. Shocket, K. Griebel*, A.T. Strauss, M. A. Duffy, C. E. Cáceres, and S.R. Hall. Allocation, not male resistance, increases male frequency during epidemics: a case study in facultatively-sexual hosts. In press at Ecology.
Hite, J.L., S. Fernández-Beaskoetxea, D.C. Medina, and J. Bosch. 2016. Joint effects of habitat, predators, host stage structure, and diversity on amphibian chytrid. Proc. Roy. Soc. London B. 283.
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.
Civitello, D.J., J.L. Hite, and S.R. Hall. 2014. Potassium enrichment stimulates the growth and reproduction of Daphnia. Oecologia 175: 773-780.
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.
Hite, J.L., D.S. Steinberg, and R. Powell. 2008. Sphaerodactylus kirbyi. Catalogue of American Amphibians and Reptiles 852: 1-2.
Steinberg, D.S., J.L. Hite, and R. Powell. 2008. Sphaerodactylus vincenti. Catalogue of American Amphibians and Reptiles 853: 1-6.
In the works (full manuscripts in review/revision)
Orlando, P.A., Hite. J.L., and Spencer R. Hall. Stage structure increases opportunities for fluctuation-dependent coexistence. In review
Shocket, M.S., D. Vergara, A.J. Sickbert, J.M. Walsman, J.L. Hite, A.T. Strauss, M.A. Duffy, C.E. Cáceres, and S.R. Hall. Past and current temperature jointly influence parasite transmission and shape seasonality of epidemics. In press, Am. Nat.
Strauss, A.T., J.L. Hite, M.S. Shocket, M.A. Duffy, C.E. Cáceres, and S.R. Hall. Colliding ecology and evolution of the dilution effect: Rapid host evolution rescues hosts from competition and disease but elevates the density of infected hosts. In review
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 prep
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
Outreach: Combining Art & Science
Outreach is an essential component that strongly informs my approach to teaching and research and vice versa.
In 2014, I began working with the local Audubon Chapter (Sassafras Audubon Society) to 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 swifts are pretty amazing and entertaining critters whose populations appear to be declining quite drastically (i.e., IUCN “near threatened” in the US, COSEWIC “federally threatened” in Canada).
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 8 "functional sculptures" and led numerous outreach projects to:
(1) provide new 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:
Pop-up card from an art-science class on 'City Birds' at Harmony School
Teaching & Mentoring
I have been fortunate to teach a variety of classes and mentor several outstanding undergraduate students.
Two unifying principles guide my teaching and mentoring approach:
(1) combining foundational principles with practical application
(2) guided active learning
I believe this approach helps to ensure a higher level of understanding, critical thinking, empowerment, enthusiasm for learning, and student engagement.
I frequently 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.