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Maintenance of Genetic Variation in a Salt Marsh Plant

PIs: R. M. Mauricio (Dept of Genetics, Univ of Georgia, Athens, GA, USA) and C. L. Richards (Dept of Plant Biology, Univ of of Georgia, Athens, GA, USA)

Support: Georgia Sea Grant College Program.

Timeframe: 2004

Project Objectives and Overview:
1) To determine if plants are adapted to local conditions in contrasting salt marsh environments.
2) To characterize how selection varies across contrasting salt marsh environments.
3) To identify whether correlations among traits may constrain adaptive evolution.

Our research is conducted on Sapelo Island, Georgia, which contains some of the last unaltered salt marshes along the Atlantic coast. These pristine marshes form a key component of both the SINERR and the GCE-LTER. The current research is focused on the Sea Oxeye Daisy, Borrichia frutescens because this species occurs across a broad range in environmental factors (for example, salinities range from 25 ppt to over 100 ppt) and exhibits extreme trait variation (heights from over 100 cm to less than 10 cm) making this species ideal for studying the action of selection across contrasting salt marsh environments. This C3 composite is abundant in the high marsh, which is marked by infrequent tidal flooding. Recent studies have shown that Borrichia tolerates high substrate salinities by increasing succulence, actively taking up sodium and other ions as well as manufacturing the nitrogen rich compatible solutes proline and glycine-betaine. Borrichia reproduces both clonally and sexually. Although the relative contribution of each type of reproduction is currently unknown, preliminary results suggests that there is sufficient genotypic variation on which selection can act. Previous work has also shown that genetic neighborhood sizes in Borrichia are relatively small, indicating that gene flow may be limited enough to maintain genetic differentiation of plants at opposite ends of the gradient.

This work synthesizes the ecology, physiology and genetics of an important salt marsh plant species to deepen our understanding of microevolution in natural plant populations. These results will increase our understanding of the mechanisms underlying salt marsh plant ecology and evolution and thereby greatly enhance salt marsh conservation and restoration efforts.


Richards, C. L. (2004). Evolution in closely adjacent salt marsh environments. PhD thesis, University of Georgia.

Richards, C.L., L.A. Donovan, and R. Mauricio. In prep. Selection, but no local adaptation of plant physiological traits in contrasting salt marsh environments. To be submitted to Evolution.

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This page was updated October 13, 2006