Hybrid Spartina Forum
Article for Cal-IPC News by Ingrid Hogle

A unique assemblage of managers, agency personnel, representatives of environmental organizations, environmental consultants and world-class research scientists gathered for two full days to learn about and discuss the “end game” of invasive cordgrass eradication at the recent Hybrid Spartina Forum. Held March 10-11 at Oakland’s Preservation Park, the forum drew a crowd of 85 participants all of whom hold a stake in deciding the fate of hybrid Spartina in the San Francisco Estuary.

The forum was timely as the State Coastal Conservancy (SCC) marks the10th year of its San Francisco Estuary Invasive Spartina Project (ISP). The SCC initiated the ISP in 2000 with the goal to reverse the spread of invasive Spartina, and to eradicate it from the Estuary if possible.

This invasive Spartina is primarily a result of hybridization between the native Pacific cordgrass (Spartina foliosa) and smooth cordgrass (Spartina alterniflora) from the East Coast which was introduced by the Army Corps of Engineers in the 1970s. The resulting hybrid plants, discovered and documented by scientists at UC Davis in the late 1990’s, were found to be extremely invasive “ecosystem engineers” that threatened the integrity of marshes, mudflats, flood control channels, mosquito abatement efforts and habitat restoration efforts around the Bay.

Successful, coordinated, regional treatment of invasive, hybrid cordgrass by the ISP since 2005 has led to a 10 fold reduction in Spartina acreage throughout the Estuary. However, genetic results indicating presence of hybrid spartina in sites that appear to contain only pure Pacific cordgrass complicate the issue of when and what to treat, and thus complicate the definition of eradication. The devil is truly in the details of how one defines the target of eradication.

SCC Project Manager Marilyn Latta kicked off the forum with the announcement that the Conservancy expects control to be completed by 2013, and expects continued monitoring for zero net acres through 2016. ISP Project Director Peggy Olofson explained that eradication of all discernable hybrids is possible, and that the challenge is now to determine what to do about those hybrids that are not discernable. The question, she posed, is “how far do we go?”

The forum was designed to provide an opportunity for thoughtful consideration this question in light of the management objectives of stakeholders. Participants were asked to consider the likely impacts of continued elimination of discernable S. alterniflora x foliosa hybrids from the marshes and mudflats of the San Francisco Bay in light of their organization’s mission and the tidal ecosystem goals for the entire Estuary.

To inform the consideration of this question, a multitude of invited speakers proceeded to give presentations on topics ranging from genetics to restoration, and from ecology to federal endangered species policy.

Geneticist Valerie Hipkins from the USDA National Forest Genetics Lab spoke about the unique challenges of conducting management-based genetic work. Malika Ainouche travelled from her lab in France to explain the complexities of Spartina evolution, explaining that the degree of genetic divergence between S. foliosa and S. alterniflora is very small and discussing work done in her lab
on similarly closely related hybrids of different Spartina species. Tom Witham discussed his work on hybrid cottonwoods, eucalyptus and other species which indicates that minor variation in genotypes within a species can impact the accumulation of heritable traits, and that these traits even include community composition and ecosystem diversity. His work suggests that changes to the genetic structure of a species within a site can change the community of other plants and animals supported by that species, and may ultimately affect the evolution of the entire community.

Joy Zedler discussed the ecology of the native Spartina foliosa, especially as it grows in southern California, where it appears to have great phenotypic plasticity in response to wet or dry years, and where she has found a long period of low salinity a requirement for its establishment in restored marshes. She compared the hybridization of Spartina in northern California to the hybridization of Typha in the Great Lakes, concluding that it is too late to control invasive Typha, but that there is hope for Spartina.
Dan Simberloff discussed examples of other invasive, hybrid species and cautioned that in no success stories of eradication has there been an issue of hybridization. With regard to the eradication of hybrid Spartina, he pronounced: “If you succeed…it would be the greatest triumph of invasion biology.”

Marc Holmes of the San Francisco Bay Joint Venture described the history of tidal marsh restoration in the San Francisco Bay, putting into perspective the impressive size and extent of current restoration projects underway in the Bay area and emphasizing how each project builds on the successes of previous projects. John Bourgeois of the South Bay Salt Pond Restoration gave an overview of the planning process and current activities of this incredibly large and ambitious restoration project. Both the ISP and the South Bay Salt Pond Restoration are projects managed by the State Coastal Conservancy. Bourgeois discussed conversations that have taken place between his project and the ISP regarding best practices to use when moving forward with restoration knowing that invasion by hybrid Spartina threatens the success of restoration, and creation of new habitat for invasion threatens to delay the success of invasive Spartina eradication.

Diane Elam of the U.S. Fish and Wildlife Service presented an impressive number of case studies involving endangered species and hybridity. She gave examples illustrating case-by-case listing, delisting, and recovery action decisions for each species based on scientific evidence, current botanical standards and species definitions, and concluded by emphasizing that the Service plans to continue employing a case-specific criteria to all listing decisions and recovery planning efforts involving hybridizations.

In addition to the many speakers, participants had a chance to see first-hand the challenge of discerning pure S. foliosa from hybrid Spartina though an impressive display designed by ISP field staff, which included live plant samples (previously frozen during the field season!), photos, maps and score cards of morphologic and environmental characteristics of each sample. Participants had the chance to vote on the species of each sample, and on Day 2 the field identifications of staff and the lab identifications from microsatellite testing were revealed!

On each day, participants were assigned to one of four break-out groups to discuss a question and then report back to the whole group. On Day 1, their exercise was to describe the main impact of invasive, non-native Spartina in terms of the mission of their organization, and to describe their organization’s current goal with regards to Spartina. On Day 2, the question was “Do you care if any hybrid alleles are left? If so, why? If not, why not?” In other words, does it matter to you and/or your organization if any genetic variability not present in pure native S. foliosa prior to the introduction of S. alterniflora, remains in any of the spartina left behind by the ISP that is not visually discernable as hybrid spartina.

Consensus was not the goal of this exercise, and differences in opinions were encouraged by facilitator Debra Rogers. However, a consensus did seem to arise in which participants acknowledged that the goal of removing every last allele from every last non-discernable hybrid plant was unrealistic.

There were suggestions regarding how to prioritize monitoring, both in terms of field monitoring and in terms of genetic testing. There was discussion about the paramount importance of ecosystem function. Some scientists called for more information through monitoring, managers called for less impact through less monitoring. Managers from Oregon and Washington expressed concerns that hybrids not be allowed to escape to their states.
There were numerous calls for common garden studies to inform the targeting of plants with invasive capabilities. There was talk about the importance of targeting functional traits rather than
neutral genetic markers. PhD student Laura Feinstein spoke of her common garden and her work on associative mapping of functional traits, and encouraged more research in this direction.

At the end of the forum, participants seemed to echo one another that the tidal wetland conservation community should prioritize the big picture goal of conserving and restoring tidal ecosystem functions. Participants seemed to be generally comfortable with the idea of allowing neutral hybrid spartina alleles to remain, after concluding that the detection and removal of all hybrid alleles was simply not feasible.

Fears that those alleles left behind from hybrids might be able to recombine and allow the re-emergence of undesirable invasive traits in future generations of plants was a strong concern. Such a re-emergence of invasive spartina traits could once again threaten the ultimate goal of maintaining and restoring the existing tidal ecosystem function in the San Francisco Bay. This forum was funded entirely by the American Recovery and Reinvestment Act through a grantfrom National Oceanic and Atmospheric Administration.