The salt marsh grass Spartina anglica originated on the coast of England as a hybrid of European and

Allopolyploidy is a process of speciation initiated by hybridization of two different species. S. anglica arose initially as a cross between S. maritima, a European species, and S. alterniflora, a North American species. At least one of these hybrid plants later doubled its chromosome number, making it capable of sexual reproduction, and produced a new species: S. anglica. From its centre of origin in Lymington, Hampshire, England, S. anglica spread northward along the coasts of the British Isles. During this same period, it colonized the coast of France and was widely planted elsewhere in northwest Europe as well as along the coasts of New Zealand, Australia, and China. The Chinese population of this salt marsh grass, established from only 21 plants in 1963, grew to cover 36,000 ha by 1980. S. anglica is extensively planted for stabilizing mud-flats because it is more tolerant of periodic inundation and water-saturated soils than most other salt marsh plants. This environmental tolerance is reflected in the distribution of the plant in northwestern Europe, where it generally inhabits the most seaward zone of any of the salt marsh plants.