Salt tolerance underlies the cryptic invasion of North American salt marshes by an introduced haplotype of the common reed Phragmites australis (Poaceae)
Over the past 50 years, U.S. Atlantic coast salt marshes have been invaded by a non-native strain of the common reed, Phragmites australis. The non-native strain, which probably originated in Europe, grows in dense, monotypic stands that crowd out native Spartina plants and lower the habitat value of the marshes for birds, fish, and other wildlife. The authors herein report upon the mechanisms that have allowed the non-native strain to become an invasive species. In controlled growth trials, the non-native strain was able to grow at much higher salinities than native (non-invasive) reed populations. The non-native strain also produced more shoots per gram of root tissue and had higher relative growth rates than the native populations on both freshwater and saline water treatments. The high salt tolerance of the invasive strain explains its spread in coastal salt marshes in the United States.
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