Sexual reproduction and population genetics of the clonal dioecious macrophyte Vallisneria americana Michx.

Populations of clonal species are predicted to be genetically depauperate compared to non-clonal species, as clones growth tends to be the primary mode of reproduction in these populations. Vallisneria americana is a dioecious, clones aquatic macrophyte that regularly flowers and produces seed. Sites from the Great Lakes (20) and Florida (5) were assayed for allozyme polymorphisms. The sites were found to be genetically variable (mean H exp = 0.216), and multiclonal (D range 0.744--0.967). Little genetic differentiation was detected among Great Lakes sites (FST = 0.038); Florida sites were somewhat differentiated (FST = 0.122) corresponding to geographical disjunction, and were significantly different from Great Lakes sites (FST = 0.124). This lack of differentiation among sites within a water system, coupled with high levels of genetic variation and clones diversity, suggest that sexual reproduction and gene flow are significant evolutionary processes in V. americana populations. Studies of sexual reproduction in V. americana showed that male and female shoots did not differentially compete with each other, nor were they allelopathic. Nutrient regimes, sediment composition and light differences were not correlated with flowering, seed production and biomass at three sites in the Huron-Erie corridor. In controlled pollinations, outcrossing and inbreeding effects were not detected in seed production or seedling vigour measures in crosses between nearby mates nor between distant mates. Differences in seedling performance were, however, associated with maternal identity. Vallisneria americana populations in the Huron-Erie corridor were found to produce significant numbers of seeds, and maintain a seed bank. Despite an efficient mode of clonal reproduction, sexual reproduction appears to play a significant role in populations of V. americana , a finding similar to that for a range of clonal plant and animal species. This role, and the potential for significant gene flow among sites are considered in the context of population genetics and evolutionary processes in populations of V. americana.Dept. of Biological Sciences. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2000 .L65. Source: Dissertation Abstracts International, Volume: 61-09, Section: B, page: 4530. Adviser: Lesley Lovett-Doust. Thesis (Ph.D.)--University of Windsor (Canada), 2000