Interspecific competition and relative success of the endangered Great Lakes coastal dune species: Cirsium pitcheri.

Abstract

Cirsium pitcheri is studied because it is an endangered species found in a very specific environment, offering a template for recovery plans of other dunal species that are suffering diminishing populations due to lack of ecosystem management. The objective of this experiment was to determine relationships between vegetative density and success of Cirsium pitcheri, at the individual and population levels, that could be useful in the recovery of Pitcher's thistle populations. We predicted that populations of Cirsium pitcheri would thrive in areas with less than 50% cover by vegetation, and that individual plants would be most successful with a total distance between neighbors that is in the immediate range of observed neighbor distance. None of our predictions were shown to be statistically significant in this experiment. Our results in this experiment imply that vegetation density surrounding the Pitcher's thistle has little to do with plant success. Research shows that it is difficult to quantify relationships such as interspecific competition for growth space in the short-run, because of the inherent population ecology of the Pitcher's thistle. Populations vary in age and size every year due to fluctuations in seed germination because of environmental factors. Although Cirsium pitcheri is difficult to study in the short run, it should be studied in the long run because of its intrinsic value and because it can be studied as a template for recovery of other dunal species on the decline in the Great Lakes. It is important to study endangered endemic plants such as Pitcher's thistle because of the contribution they make to local ecosystems and for the intrinsic value of appreciating such a uniquely specialized plant species.