Shoreline modification affects recruitment of invasive Phragmites australis
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ORIGINAL PAPER
Shoreline modification affects recruitment of invasive Phragmites australis Melissa K. McCormick . Dennis F. Whigham . Jared R. Stapp . Eric L. G. Hazelton . Eliza K. McFarland . Karin M. Kettenring
Received: 29 October 2019 / Revised: 9 September 2020 / Accepted: 26 September 2020 Ó This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply 2020
Abstract Shoreline hardening affects ecological processes in nearshore intertidal ecosystems and upland habitats. Invasive species establishment and spread is one consequence of shoreline alterations. Invasive Phragmites australis has spread throughout the U.S., including in subestuaries with hardened shorelines. It is unclear, though, by what mechanisms shoreline hardening facilitates P. australis establishment. We tested the hypothesis that shoreline structures are associated with seedling recruitment, resulting in higher levels of within stand genetic diversity. We used microsatellite analysis to examine the genetic diversity of P. australis stands associated
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11273-020-09757-6) contains supplementary material, which is available to authorized users. M. K. McCormick (&) D. F. Whigham E. L. G. Hazelton E. K. McFarland Smithsonian Environmental Research Center, 647 Contees Wharf Rd., Edgewater, MD 20137, USA e-mail: [email protected] Present Address: J. R. Stapp Department of Environmental Science, Policy, and Management, University of California, Berkeley, 130 Hilgard Way, Berkeley, CA 94709, USA E. L. G. Hazelton K. M. Kettenring Department of Watershed Sciences and Ecology Center, Utah State University, Logan, UT 84322, USA
with two types of shoreline structures (riprap, bulkhead revetments) compared to unaltered shorelines. Because P. australis seed viability depends on crosspollination, higher levels of genetic diversity in stands associated with hardened shorelines are more likely to contribute to the spread of invasive P. australis. We conclude that the extent of shoreline modifications in the Chesapeake Bay has contributed to the spread of P. australis by seeds. The results have implications for the management of P. australis associated with the establishment of shoreline structures. Keywords Phragmites australis Invasion Genotypic richness Shoreline hardening Wetland
Introduction Hardening of shorelines by adding vertical bulkheads, sloped riprap revetments, groins, jetties, or breakwaters is widely used around the world to combat shoreline erosion and the resulting loss of property (Dugan et al. 2011; Ache et al. 2013; Gittman et al. 2015; 2016). In some estuarine systems in the U.S., hardened shorelines can cover more than 70% of the shoreline (Gittman et al. 2015). In the Chesapeake Bay, a survey of 100 subestuaries found that eight had more than 50% shoreline hardening, and 23 had between 30 and 50% (Living Shoreline Summit
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