My Work with Pitcher's thistle
Since 2011, I've worked with federally threatened Pitcher’s Thistle (Cirsium pitcheri) both at Chicago State University (as a graduate student and assistant) as well as the Morton Arboretum (as a Conservation Intern). I've conducted population viability analyses on several C. pitcheri populations spanning Indiana, Illinois, and Wisconsin as well as determined growth trajectories, estimated the impacts of weather and the effect of seed sources on the establishment of the only reintroduced population in Illinois. Below are some of the projects, I've exclusively worked on and have published or in the process of publishing. For more info on Pitcher's thistle visit http://www.pitchersthistle.org/ .
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Reintroductions in Meta-populations
My master’s thesis focused on the management and restoration of an Pitcher’s Thistle (Cirsium pitcheri) from a meta-population perspective in Indiana. Three native populations have been monitored since 1988 (the year I was born) by Kathryn McEachern. In 1994, she planted 3 restoration population, of which 2 successfully established. Using a 23 year data set, my objective was to determined how the viability of the current Indiana meta-population has responded to the addition of two new populations via Population Viability Analysis. Conclusion from this research was that while the reintroduction of populations improved meta-population viability, management effort would be better spent maintaining the current populations, possibly through enhancements rather that creating new population. This study has been published in Restoration Ecology.
Building upon this, I examined the relative contributions of each population in respect to their population life-history strategies using sensitivity analysis to determine which aspect of the population (Growth, Survival or Reproduction) requires greater attention from the management. This study has been published in Ecosphere |
Last year in the Society for Ecological Restoration news, I got a little bit of press for my first published manuscript.
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Microhabitat and restorations
When reintroducing a species, practitioners face several challenges, such as identifying optimal habitat. Knowing the precise microsite requirements of a species can allow for restoration efforts to be directed in a way that is more effective both in terms of time and cost. In this study, we evaluate effects of transplant size and microhabitat on restoration success of the federal threatened Pitcher's thistle, Cirsium pitcheri using a dataset of transplants planted over a 10-year period beginning in 1991. Using general and generalized linear models, we determined how microhabitat variables influenced first year transplant survival and growth. Our data show that the probability of first year survival is influenced by the size at transplantation. We also found that the characteristics of plant microhabitat influence plant growth with C. pitcheri planted at higher elevations growing larger and those on steeper slopes regressing to a smaller size. Slope also influences the amount of sunlight received, with flatter slopes receiving more sunlight. These results have the potential to direct restoration efforts. Depending on the resources available we recommend that in the context of a one-time reintroduction effort, the best option for success may be maximizing plant size to ensure the greatest survival. For restoration to be more effective, more research is needed to identify the habitat that is suitable for transplant success.
This study has been published in Ecological Restoration.
This study has been published in Ecological Restoration.
Spatially Explicit Population Viability Analysis
Plants inhabit spatially and temporally heterogeneous habitat with various landscape characteristics influencing growth, survival and reproduction. Utilizing microhabitat variables such as slope, elevation and aspect can allow for a spatially explicit approach to understand the important ecological drivers of population persistence. By applying knowledge about individual plant demographics and their response to microhabitat variables, inferences into how the entire population responds over time are made possible. We used a spatially-explicit individual based modelling (SEIBM) approach to model the population demographics and distribution of a restored population of Cirsium pitcheri in Illinois. Using regression analysis, we estimated model parameters for survival, growth and reproduction which were subsequently chosen by comparing observed and projected abundances. Projected population abundances followed the same trajectory as the observed abundances for our chosen model. Using that model, 100-year projections revealed that this Illinois Beach population has a median time to extinction (MTE) of 20 years, presenting a slightly more optimistic outlook for C. pitcheri as compared to traditional matrix modelling approaches. We then analyzed how landscape characteristics influenced plant occupancy via hotspot analysis to determine optimum locations. Optimum plant habitat include low, east-facing slopes with elevation having limited influence. This approach presents a formal modeling exercise for using spatially explicit, individual-based models to conduct population viability analysis. By comparing this SEIBM approach to matrix modelling methods, we affirm that SEIBM are a valid tool for population viability analysis while also having the ability to include information that is spatially explicit to the habitat upon which C. pitcheri occupies. This study has been published in Ecological Modelling.