Isozyme variation and genotypic diversity in three different-aged populations of Ammophila breviligulata (Fern.) (American beachgrass) were investigated in order to determine the nature and causes of intra-species changes during sand dune succession. Ramets of Ammophila breviligulata were collected along three randomly located transects in each of three populations on Castle Neck, a barrier island in Ipswich, MA. Populations ages (I $<$ 7 yrs., II = 10-20 yrs., III $>$ 35 yrs.) were estimated by examining a series of aerial photographs taken over the last 35 years. The ramets were randomly transplanted to a common field plot in Amherst, MA. Ten soluble isozyme systems extracted from young leaf tissure were surveyed in a total of 300 transplanted ramets using starch gel electrophoresis and the zymogram technique. Microgeographic differentiation of populations has occurred with respect to particular allozyme phenotypes. Significant differences were found among study populations in the frequencies of allozyme phenotypes at three of seven polymorphic isozyme loci (Duncan's multiple range test, p $<$ 0.05). Factors such as random drift, founder effects, and natural selection may have contributed to the differences in phenotype frequencies among populations. Changes in population structure appear to have occurred with time. Significant differences were found among populations in the frequencies of 19 multilocus genotypes (G-test, p $<$ 0.05), suggesting that populations may consist of ecotypes. Genotypic diversity increased significantly with greater population age (Duncan's multiple range test, p $<$ 0.05). The mean number of populations in which a genotype was found was significantly higher in the younger population than in the older population (Duncan's multiple range test, p $<$ 0.05). These results suggest that changes toward increased genotypic diversity and increased niche specialization of genotypes occurred within the populations during sand dune succession. The inter-species changes found in this study parallel the inter-species changes found in other studies of ecological succession. The high degree of genotypic differentiation among populations has implications for those who use Ammophila breviligulata in beach stabilization efforts. Current dune management techniques involve planting dunes with a single genotype. This study indicates that monoculture of man-made dunes should be abandoned in favor of planting various genotypes better adapted to the particular environmental conditions.
| Identifer | oai:union.ndltd.org:UMASS/oai:scholarworks.umass.edu:dissertations-6917 |
| Date | 01 January 1987 |
| Creators | CARLSON, LARS HERBERT |
| Publisher | ScholarWorks@UMass Amherst |
| Source Sets | University of Massachusetts, Amherst |
| Language | English |
| Detected Language | English |
| Type | text |
| Source | Doctoral Dissertations Available from Proquest |
Page generated in 0.0058 seconds