Add to ORKGAbstract. Spartina alterniflora, a perennial grass native to the North American Atlantic coast, was introduced during the 19th century in western Europe (Southern England and western France) where it hybridized with the native Spartina mariti-ma. In England, the sterile hybrid S. · townsendii gave rise by chromosome doubling to the highly fertile allopolyploid Spartina anglica, which has now invaded many salt marshes and estuaries in western Europe, and has been introduced in several conti-nents. In South-West France, another sterile hybrid was discovered in 1892 in the Bidassoa Estuary, and named Spartina · neyrautii. According to their morphology, some authors suggested that S. · neyrautii and S. · townsendii result from reciproca