Examining the Potential for Local Adaptation of Apocynum cannabinum Populations at an Abandoned Limestone Quarry

Bryan Helm, Science Research Fellow

in collaboration with Dana Dudle, Vanessa Fox, David Pope, and Aaron Randolph

Click below to download:
Bryan Helm's poster (powerpoint; 5.1 MB)
Bryan Helm's report (microsoft word; 6.0 MB)

Abstract:

The DePauw University Nature Park’s diverse microhabitats provide a unique opportunity for ecological research, especially combined with the knowledge of the recent history of land use. Formerly a limestone quarry, it offers a unique opportunity to look into the biology of colonizing species and the selective pressures imposed by human-induced succession. Specifically, Apocynum cannabinum, a native perennial weed was chosen for study because of its presence in and around the abandoned limestone quarry. To identify the possibility of local adaptations that allowed A. cannabinum to survive in the quarry bottom, variations in the plants had to be documented. A comparison study was conducted between two sites of A. cannabinum, one in the quarry bottom (QB, Quarry Bottom) and one in a nearby wet meadow (QRS, Quarry Roadside). Random samples were taken from both sites also.

Our hypothesis was that the plants in the quarry bottom would be stressed because of the harsher environment, and would therefore not be able to flower or fruit as much. Populations density, flowering individual density, number of umbels, and number of fruits were sampled from “patches” of A. cannabinum in the quarry bottom and from the wet meadow population. In addition we took data on the microsite types in those patches, and collected soil for water content.

We found that the microsite types differed significantly between the quarry roadside and quarry bottom, and there was more water in the quarry roadside soil than the quarry bottom soil. The microsite types did not differ between the A. cannabinum patches and random samples from either site. This shows that the two environments were much different, but there was not much of a difference between sites where A. cannabinum grew and random samples. The patchy distribution of the A. cannabinum population indicates that microsite or soil conditions suitable for germination and/or vegetative spread of this species may be rare in the QB relative to the QRS. We also found that the population of A. cannabinum in the quarry roadside was more robust, having an overall larger population density, more flowering individuals overall, more umbels per area, and more fruits per area. Plants in the quarry roadside were more likely to flower than in the quarry bottom; however, we found that the number of umbels and number of fruits per flowering individual did not differ between the two sites. This shows that some individuals are able to overcome a harsher environment. The barrier for the plants in the quarry bottom seems not to be in their ability to produce fruits or inflorescences, but in flowering initially. It may be that intense competition at the QRS, prevent higher levels of flower and fruit production at the QRS, despite the less stressful conditions.

Bryan's poster
Bryan's report