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Alyxia

Vallisneria restoration site Human-induced changes declines in submerged aquatic vegetation (SAV) in the Chesapeake Bay have both been caused by and led to declines in water quality. It was once a dominant freshwater and oligohaline species, but, along with most coastal submersed aquatic macrophyte species, it has declined in abundance and distribution (Shafer & Bergstrom 2010) due to stressors that act across a range of spatial scales. Thus, it provides opportunities for theory development and for applying theory to restoration and conservation.

The far-reaching consequences of SAV decline have focused attention on effective ways of restoring these components of the Bay's living resources. Resulting restoration efforts of SAV in the Chesapeake Bay have been impressive; however, success has been undeniably mixed. In collaboration with Dr. Katia Engelhardt at the University of Maryland Appalachian Laboratory, we were funded by Maryland SeaGrant to assess the role genetic diversity and sources of restoration stock on restoring Vallisneria americana. At the same time, we have evaluated the effect of restoration on genetic diversity patterns.

We are interested in V. americana because it was once a dominant species in the Chesapeake Bay, it is considered an keystone food resource for wildfowl, it does not interfere with recreational uses of waterways, and it is used in restoring portions of the Bay by a variety of conservation groups. This submersed aquatic macrophyte is dioecious and is capable of both clonal growth and sexual reproduction vegetative expansion has been considered the dominant form of reproduction.

Katia at Conococheague Creek

Changes in the distribution of SAV including V. americana are monitored using remote sensing techniques by the Virginia Institute of Marine Science. The remotely sensed locations are ground truthed by a dedicated network of agency personnel and volunteers. Thus, historic and current distributions are relatively well known.

The role of genetic diversity in ecological functioning is increasingly recognized as being analogous to the role functional species diversity.Three aspects of genetic diversity are known to fundamentally affect plant fitness and thus probabilities of persistence and potential for restoration success: levels of inbreeding within individuals, levels of diversity among individuals, and adaptation of individuals to local environments. Through a combination of field, laboratory a greenhouse observations and experiments we have been examining the effects of each of these aspects of diversity.

Knowledge of the distribution of genetic diversity within and among populations can guide selection of appropriate donor individuals and populations for restoration. For example, quantifying the number and spatial extent of clones within populations will contribute to generating collecting protocols that increase the potential genetic diversity in restoration stock.

The Boys in the Bay Creek

During 2007 and 2008 Michael Lloyd (Ph.D student) and Robert Burnett (research assistant) spent lots of time in waders, in boats, and in snorkeling gear sampling both natural (n=26) and restored (n=8) populations of V. americana from throughout Chesapeake Bay and its tributaries. When they were not on or in the water, Mike and Robert were in the lab characterizing genetic diversity using microsatellite markers.Map

The sampling design has allowed us to assess the spatial and environmental patterns of genetic diversity in natural beds and to compare those patterns with restored beds of varying ages. Katia has used individuals with known genotypes in controlled environment experiments that are improving our understanding of linkages between neutral genetic diversity and ecological function. In particular we are evaluating fitness related characteristics such as asexual and sexual reproduction, vegetative growth rates, and tolerance to adverse environmental conditions.

Based on our extensive and ongoing work we know that local sites within the Chesapeake Bay vary in genotypic richness from dominance by a single clone to all samples being unique genotypes and some genotypes extend for ~50-160 km along the Potomac River (Lloyd et al. 2011). Variation in clonal dominance appears to be correlated with ecological contexts that affect population extent and dispersal (linear riverine habitats versus oligohaline estuarine environments). Populations also vary in the degree of relatedness among genotypes. Significant genetic structure among populations based on microsatellite diversity is coincident with environmental factors (e.g., tidal influence and salinity. Katia at Conococheague Creek

Brittany West (graduate student) is expanding the work we are doing in the Bay to examine patterns of genotypic and phenotypic diversity and multiple scales within regions along a latitudinal gradient from Maine to Florida.

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