UVM Theses and Dissertations
Format:
Print
Author:
Yankel, Christine
Dept./Program:
Botany and Agricultural Biochemistry
Year:
2004
Degree:
M.S.
Abstract:
Clonal reproduction is a common process in many plants, the frequency and pattern of which can influence the genetic structure and the evolutionary potential of populations. Despite this, relatively little attention has been given to the production of clonal propagules that are dispersed (as opposed to attached offshoots). In Cystopteris bulbifera, bulbils, specialized clonal reproductive structures are produced on the underside of the fern frond. The goals of this project were to determine the extent of clonal reproduction in this fern, and to see how this unique mode of reproduction affected he distribution of genotypic and genetic diversity within and between populations, and whether bulbils might potentially serve for dispersal within and between populations.
Ferns from four populations in the Champlain Valley of Vermont were mapped, and fronds collected. A microsatellite marker was developed and used in conjunction with amplified fragment length polymorphisms (AFLP)- to genotype the mapped plants. A total of 46 unique genotypes were identified among the 60 plants genotyped with the two marker types, yielding an average proportion distinguishable (PD) of .75. The average size of a clone, Nc, was 1.3 copies, though the number of copies of each clone varied, with the most common present in four copies. Genotypes were all local, with any given genotype restricted to a single population. Within a population, clonal reproduction resulted in some patchiness of genotypes, with clonemates more clustered 0-6 meters of each other than would be expected by chance. There was a large amount of genetic differentiation between populations, suggesting limited gene flow between these populations, with no apparent correlation between geographic distance and genetic distance.
The most genetically similar populations (Nei's genetic distance of.07) were separated by a distance of almost 60 kilometers, while two populations separated by less than one kilometer were much more different (Nei's genetic distance of .26). Thus, it appears that bulbils serve only in limited dispersal and reproduction within populations of Cystopteris bulbifera, and there is no evidence of their dispersal between even very close neighboring populations.
Ferns from four populations in the Champlain Valley of Vermont were mapped, and fronds collected. A microsatellite marker was developed and used in conjunction with amplified fragment length polymorphisms (AFLP)- to genotype the mapped plants. A total of 46 unique genotypes were identified among the 60 plants genotyped with the two marker types, yielding an average proportion distinguishable (PD) of .75. The average size of a clone, Nc, was 1.3 copies, though the number of copies of each clone varied, with the most common present in four copies. Genotypes were all local, with any given genotype restricted to a single population. Within a population, clonal reproduction resulted in some patchiness of genotypes, with clonemates more clustered 0-6 meters of each other than would be expected by chance. There was a large amount of genetic differentiation between populations, suggesting limited gene flow between these populations, with no apparent correlation between geographic distance and genetic distance.
The most genetically similar populations (Nei's genetic distance of.07) were separated by a distance of almost 60 kilometers, while two populations separated by less than one kilometer were much more different (Nei's genetic distance of .26). Thus, it appears that bulbils serve only in limited dispersal and reproduction within populations of Cystopteris bulbifera, and there is no evidence of their dispersal between even very close neighboring populations.