Clonal Diversity and Resistance
Claus Holzapfel, RUN Department of Biology; Francisco Artigas, MRRI Director; Edward Kirby and Huimin Man, RUN Department of Biology
Large portions of brackish marsh have been invaded by non-native genotypes of the common reed (Phragmites australis). Within the Hackensack Meadowlands only fractions are still (or again) dominated by low marsh Spartina alterniflora and high marsh Spartina patens (both being native species). From the latter species, only isolated patches remain that nevertheless appear to be stable (Artigas pers. com.). These patches vary in size and seem to resist encroachment by other species through their peculiar growth form: the formation of dense “cowlick” mats consisting of prostrate grass shoots. This high marsh has been used in historic time for hay making (Smith 1942) or was burned to facilitate goose grazing and/or muskrat trapping. Current dense mats of S. patens apparently developed after these management practices ceased. Today, the presence of the Spartina high marsh is contributing to the landscape diversity and species diversity in the Meadowlands and is attracting a wide range of wildlife.
We are interested in exploring the factors that allow these patches to persist in the presence of dominant and highly competitive Phragmites. In particular we would like to investigate (a) whether the peculiar prostrate growth form of S. patens allows it to compete with other species and (b) whether larger patches of S. patens consists of more competitive clones than small patches. Three goals drove the initial stage of this research:
Methods and Results:
We propose a series of pilot experiments that will compare the strength of both the dispersal and pollination filters at the species and community levels.
Genetic description of clonal structure of patches
Descriptive measurements of the effects of S. patens mats on isolated stems of competitors such as Phragmites australis
Conclusions and outlook
We found evidence that border zones between Phragmites and Spartina patens stands are different between small or large remnant patches of Spartina high marsh. The fact that the stand overlaps in these border areas are smaller and the border therefore sharper, suggests that differences in competitive interaction exist.
The preliminary result, that the sampled Spartina patens clones have very similar genetic structure, has to be confirmed with additional studies. These are currently conducted by graduate student Tingling Wu in cooperation with the lab of Edward Kirby.