Recent and rapid losses in plant diversity due to habitat loss and climate change have been documented and may be underestimated. Studies of endangered plants often focus on niche-based approaches, which include range analyses, life history studies that document demographic responses to various environments, and physiological studies of particular limiting factors. Despite many rare plant species being dispersal limited, a neutral approach is underrepresented in studies of endangered and rare plants. Pitcher’s thistle (Cirsium pitcheri), a federally threatened and state endangered dune species endemic to the Great Lakes, is threatened by climate change, habitat degradation, and invasive species. Although numerous studies have documented C. pitcheri natural history and demography, subsequent restoration efforts have not been entirely successful, and work continues on finding optimal reintroduction environments. In a remnant, thriving natural population of C. pitcheri on a remote island in Lake Michigan, we used transect surveys to correlate C. pitcheri presence with large-scale environmental factors across dune gradients, followed by fine-scale monitoring of individual plant growth with Arduino-based sensors to identify which environmental factors yielded greater growth within a season.
Results/Conclusions
We found that, as in previous studies, C. pitcheri on Beaver Island is generally more prevalent on open dunes that are dry, exposed to the sun, and have high soil temperatures. However, despite their prevalence, individual C. pitcheri plants did not actually perform better, as measured by seasonal leaf vegetative growth, within this microclimate compared to wetter, cooler, or more shaded microclimates. Furthermore, short-term growth did not correlate with fine-grained environmental factors monitored by in situ sensors. We conclude that the distribution and success of this rare plant may well be linked to stochastic and very localized dispersal. We suggest that a neutral or dispersal-based approach should be given stronger consideration in endangered species conservation efforts.