26 June 2006
Project Title: Determination of Genetic Diversity and Restoration Potential of the Pitcher Plant (Sarracenia purpurea) in the Lake Superior Watershed.
Principal Investigators: Jennifer M. Karberg, Margaret R. Gale
Semi-Annual Progress Report – FY2006
Research Purpose:
The purpose of this study is to characterize the genetic diversity, and potential restoration of Sarracenia purpurea (the northern pitcher plant) in forested wetlands, particularly in the Great Lakes Region. Sarracenia purpurea is a prominent component of forested peatlands in the Great Lakes Region, a habitat type that is becoming increasingly scarce with development. Many federal and state agencies have shown interest in the importance of including this plant species in wetland restoration plans, particularly the Indiana Dunes National Lakeshore for the purposes of this study. In order to perform successful restoration, there is much still to learn about Sarracenia purpurea and how it interacts with surrounding communities.
One issue we are examining is the pattern of gene flow that exists between established populations around the Great Lakes. Some of these populations are found on potential isolated island systems such as Isle Royale National Park and the Apostle Islands National Lakeshore. We are attempting to examine if these island populations are genetically different from mainland populations on the Keweenaw Peninsula, Sleeping Giant Provincial Park in Canada and Pictured Rocks National Lakeshore. This would hopefully give an idea of dispersal distances of the plant, gene flow across long distances and if the plant tends to adapt to individual microhabitats. We would also like to examine the range of genetic diversity available to this plant to aid in planning restoration. This information would help locate viable seed sources for restoration if (a) the plant has not local adaptation or (b) seed sources must be selected locally for successful restoration. Information obtained from this project will help in the planning of restoration of Sarracenia purpurea in Cowles Bog at Indiana Dunes National Lakeshore.
Research progress 2003-2006:
To answer these questions in 2003 we located peatlands on Isle Royale, Sleeping Giant, and the Keweenaw Peninsula. Genetic material was collected and the populations were surveyed for plant number, leaf number, flower number and fruit number – morphological measures with which to compare plant populations.
We discovered moderate to low genetic diversity in all of the Sarracenia purpurea populations with all of the populations fairly similar genetically. The Canadian populations were smaller in all morphological characteristics and slightly different genetically from the Keweenaw and Isle Royale populations. Because of the low overall genetic diversity we were not able to determine gene flow, mainly because this species tends to reproduce clonal and conserve genetic diversity. These populations in the Great Lakes Region probably all colonized the area at a similar time following the retreat of the last glacier and hence the founding populations would have been closely related genetically. The Canadian populations are in an area dominated by limestone bedrock, unlike the Keweenaw and Isle Royale areas. Limestone tends to create fairly alkaline conditions and Sarracenia purpurea tends to inhabit very acidic environments. The physical and genetic differences observed in populations could be related to different bedrock materials and pH quality of the Sarracenia purpurea habitats.
To further answer this question, in the summer of 2005 and 2006 we located populations of Sarracenia purpurea in more wetlands around the Great Lakes region – particularly the Apostle Islands National Lakeshore, Pictured Rocks National Lakeshore, Indiana Dunes National Lakeshore, and populations in the northern Lower Peninsula of Michigan. We hoped to encompass a variety of bedrock and pH types with this sampling method. Populations were surveyed and sampled in the same manner as the previous sites and DNA analysis is currently in progress. This will hopefully allow an analysis of how closely adapted Sarracenia purpurea populations are to their local microhabitat and help design broad and local restoration and conservation plans.
Impact:
This research is beginning to provide valuable information to land managers, National Park officers, and ecosystem restoration and creation planners. Forested peatlands are increasing in the focus of wetlands restoration and creation for a number of reasons: potential for carbon sequestration, water quality purification, and the unique nature of the habitat. For these reasons federal and state officials are looking for well thought out and successful restoration and management plans.
To create successful management plans; a thorough understanding of the ecology of some of the dominant plant species of the ecosystem is needed. The survival of these key plant species in restored and created wetlands is vital to the perceived and functional success of these sites.
This study has begun to provide valuable insights into the ecology of Sarracenia purpurea and some important considerations for restoration of these forested wetland systems, so important in northern-forested regions. In this study we expected to see that isolated populations would be genetically different due to limited gene flow across Lake Superior. If we had seen this phenomenon then restoration would require seed sources from localized regions and would require the placement of populations close enough together to facilitate gene flow.
Instead we saw no real differences related to isolation, all populations appear closely related genetically likely related to historical colonization of the area by Sarracenia purpurea at a time following the glaciers when forested peatlands were wide spread. This fact means that, when restoring populations and reintroducing Sarracenia purpurea, seeds and plants can be taken from any number of locations and still preserve the local genetic diversity. This is important for areas such as Indiana where there are very few populations left. Seed sources can be selected from areas of dense Sarracenia purpurea populations and not put a strain on the areas with low populations density or areas where the plant is endangered. This makes for cheaper, less time consuming and more successful restoration of these forested wetlands.
The second important fact already taken from this study is that the Canadian populations were beginning to be morphologically and genetically differentiated from the other populations. This small genetic differentiation was not related to distance or isolation but rather to the bedrock and substrate type of the region. It appears that this ecosystem type, although it prefers acidic conditions, can develop in alkaline regions. These populations appear to be adapted both morphologically and genetically to the alkaline condition. This indicated that restoration of populations would require an examination of the substrate quality as an important consideration when looking at seed sources and ecosystem type.
These issues raise more questions to be considered. The first part of the study did not examine pH of the various wetland types to thoroughly examine the concept of alkalinity vs. acidity. Also, in the Great Lakes region, these plants grow in purely alkaline, non-forested wetland systems. We need to understand how these systems related to our forested wetlands and what makes them unique.
Overall this study is in the process of providing valuable information related to the restoration and conservation of forested peat wetlands in the northern United States.
Remaining Work – Summer 2006:
During the summer of 2006, lab work will be completed on the genetic analysis of plant populations from the US and Canadian National Parks. These populations will be compared and conclusions regarding sources for reintroduction will be made. From this information a report on viable sources for Sarracenia purpurea restoration will be created for Cowles Bog, Indiana Dunes National Lakeshore. A final report will be submitted in December 2006 for the completion of this project.