Position: Associate Professor of Biology & Environmental Studies
Location: HLSB 347
Phone: (540) 665-4711
Email: mzimmerm4@su.edu
Employed Since: 2014
Educational History:
B.S., Biology, Muskingum College M.S., Biology, Wake Forest University Ph.D., Biology, Wake Forest University
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Fields of Expertise:
Parasitology, Host-Parasite Interactions, Ecology, Evolution, Population Genetics, and Aquatic Ecosystems
I have two major areas of research. The first area of investigation is the infection patterns of trematode parasites in aquatic mollusks and how these infections impact not only the snail communities, but other hosts in the aquatic ecosystem. Since trematodes frequently have complex life cycles, many of the hosts within an aquatic ecosystem are directly impacted by the parasites, along with avian visitors that frequent the bodies of water. Identifying seasonal patterns of infection, the distribution of the infected hosts, and the impact of the parasites on the mollusks can help identify patterns of infection and disease in a variety of hosts and lead to potential solutions to reducing the parasite burden of wildlife.
My second area of research investigates parasite infection in Bluegill sunfish (Lepomis macrochirus). Bluegill are a sport fish frequently caught by fisherman in North America, but they have some interesting aspects of their biology that are often overlooked by the amateur angler. Bluegill are sexually dimorphic in that males have a drastically different size and appearance than females. Males are larger and more colorful, oftentimes having bright orange breasts and a deep blue color on their face in addition to their olive dorsal coloration. Females on the other hand, tend to have silver body coloration with light yellow or white breast coloration. Many anglers have probably noticed these clear differences in the male and female fish they have caught, but the system has an underlying secret that goes further than their outward appearance. The Bluegill mating system actually has two male morphotypes that differ in both appearance and behavior.
The previously described large colorful male is referred to as an α-male and is dominant in terms of territoriality, behavior, and diet. These dominant males are more aggressive and often chase subordinate β-males from their territory, which leads to greater reproductive success. The α-male is responsible for nest building, courting females, and brood care and has a high energy investment into reproduction. The β-males are considered to be nest parasites and partake in either sneak mating or mimicking behaviors to fertilize eggs, but do not partake in parental care. This Bluegill mating system in which multiple behavioral males are present is referred to as an evolutionary stable system (ESSt), meaning that as long as a stable mating strategy persists in a population, multiple mating tactics may co-exist. The stable mating strategy in Bluegill is represented by the α-male that has a high amount of investment into reproduction, while the β-males that try to reproduce without high energy investment are considered a mutant strategy that is not sustainable without the α-males.Â
There are many trade-offs in this Bluegill reproductive system. For instance, β-males tend to mature sooner in an attempt to maximize their lifetime reproductive output, while α-males will invest in growth in an attempt to increase their success of courting females. However, α-males have a greater contribution to the offspring and increased reproductive success. Since α-males represent the stable reproductive strategy and are solely responsible for courting and brood care, it would be expected that α-males should be the dominant Bluegill morphotype in a population; however, this is not the case. This means that there must be some other selective pressure that either enhances β-male survival or decreases α-male subsistence. One selective pressure that is often overlooked in ecological systems is parasitism. Parasites can have monumental impacts not only on individual hosts, but entire ecosystems. Behavioral differences between the morphotypes, particularly relating to diet, may result in distinct differences in not only parasite composition, but also parasite abundance. Parasitism can have deleterious effects not only on host survival, but also host body condition and reproductive output. The role of parasites in the ESSt has never been investigated and may be impacting its maintenance and the persistence of the β-male morphotype in Bluegill populations, despite their reduced reproductive output. The main focus of my research is investigating the potential differences in parasitism between α- and β-male morphotypes to evaluate if parasites may be an influencing factor in the maintenance of the ESSt in Bluegill sunfish.
Professional Highlights:
Students conducting independent research projects under my direction are encouraged to participate in local, regional, and national conferences to present their research. These students have won a number of awards at various conferences in addition to publishing peer reviewed manuscripts.
Student Presentation Awards
2016 – SUPr Summit (Shenandoah University) – Outstanding empirical analysis in an individual project (Craig Hollander)
2016 – Warrington Symposium (Shenandoah University) – Alpha Chi Prize for best original research (Craig Hollander)
2016 – Helminthological Society of Washington – Stirewalt- Lincicome Student Paper Award, 2nd Place (Craig Hollander)
2017 – SUPr Summit (Shenandoah University) – Outstanding empirical analysis in an individual project (Brandi Griffith)
2017 – Warrington Symposium (Shenandoah University) – Alpha Chi Prize for best original research (Brandi Griffith)
2017 – Helminthological Society of Washington – Stirewalt- Lincicome Student Paper Award, 1st Place (Brandi Griffith)
2018 – SUPr Summit (Shenandoah University) – Outstanding empirical analysis in an individual project (Candace Ashworth)
2018 – Warrington Symposium (Shenandoah University) – Alpha Chi Prize for best original research (Nicholas Strait)
2018 – Helminthological Society of Washington – Stirewalt- Lincicome Student Paper Award, 1st Place (Candace Ashworth)
2018 – Virginia Academy of Science – Best Student Presentation, Natural History and Biodiversity
Selected Manuscripts (** – Denotes an SU undergraduate)
**Hollander, C. A., **B. N. Griffith, and M. R. Zimmermann. 2019. Differences in endohelminth parasite infection between male morphotypes of bluegill sunfish (Lepomis macrochirus). Journal of Parasitology, In press.
**Strait, N. S., **C. E. Ashworth, and M. R. Zimmermann. 2019. The potential role of strigeid parasite infection in the maintenance of alternative reproductive morphotypes in bluegill sunfish (Lepomis macrochirus). Comparative Parasitology, In press.
Personal Quote:The small school atmosphere and personal interactions you get with students make SU an ideal teaching and learning environment.
Personal Highlights:
Married, with one son and a dog. I enjoy being outside, particularly fishing and hiking with my family, and am an avid baseball fan.
Recommended Link(s):
A brief summary video from one of my research students can be found here: