Evolution in Spartina (Gramineae): I. The history and morphology of the genus in Britain

Abstract

SUMMARY The history of the genus Spartina in Britain is traced from herbarium records and publications. This historical information and a morphological study of living plants strengthen the view that sterile S. x townsendii arose in c. 1870 in Southampton Water as a hybrid between native S. maritimu and introduced American S. alterngora. The fertile Amphidiploid arose in 1890 and spread at the expense of the species populations. It is shown that species and hybrids of the S. x townsendii complex can be separated by a combination of only a few well‐defined morphological characters, and by stomata and pollen grain details. A polyhaploid seedling of low vigour among Amphidiploid progeny is described and its existence and resemblance to S. x townsendii F1 emphasizea the relationship between this PI hybrid and the Amphidiploid. Putative backcross hybrids of S. x townsendii Amphidi‐ ploid with X. alternijfora in Southampton Water provide conclusive evidence of S. x

Uniformity of the nuclear and chloroplast genomes of Spartina maritima (Poaceae), a salt-marsh species in decline along the Western European Coast

“…At the same time, the regression of S. maritima has been observed in British and northwest (Brittany) French salt marshes (Marchant, 1967;Raybould et al, 1991b;Guénégou and Levasseur, 1992). In Southampton water for example, all S. maritima plants have now disappeared (Raybould et al, 2000).…”

“…In Southampton water for example, all S. maritima plants have now disappeared (Raybould et al, 2000). Marchant (1967) and Des Abbayes et al (1971) suggested that the regression of S. maritima in northern Europe has been accelerated by S. anglica invasion that had supplanted S. maritima populations. However, it has also been noticed that the decay of S. maritima populations is also observed in sites where S. anglica is not present, and that the allopolyploid colonizes open bare flats rather than previously extant vegetation areas (Raybould et al, 1991b).…”

“…North European populations of S. maritima lack vigor; they are characterized by slow lateral extension of individuals that rarely reproduce sexually, while southern European and African plants are bigger, more robust and produce viable seeds (Marchant, 1967). The variation in vigor may result from more stressful environmental conditions encountered by plants introduced from Africa in Northern areas of Europe (Chevalier, 1923;Marchant, 1967).…”

“…The variation in vigor may result from more stressful environmental conditions encountered by plants introduced from Africa in Northern areas of Europe (Chevalier, 1923;Marchant, 1967). Moreover, S. maritima is usually a dominant species of the lower marsh in numerous coastal marshes and estuaries.…”

Multiple origins and genetic diversity in the newly arisen allopolyploid species, Senecio cambrensis Rosser (Compositae)

“…Within the past 110 years, four new allopolyploid species are known to have originated in the wild; two in North America, Tragopogon mirus Ownbey and T. miscellus Ownbey (Ownbey, 1950;Roose & Gottlieb, 1976), and two in Britain, Spartina anglica C. E. Hubbard (Huskins, 1931;Marchant, 1963Marchant, , 1967Marchant, , 1968Raybould et a!., 1991a) and Senecio cambrensis Rosser (Rosser, 1955; Abbott et a!., 1983). The discovery of these new species soon after their origin has presented an excellent opportunity for detailed analysis of the process of allopolyploidy, now regarded as a mode of speciation of great significance in the plant kingdom (Lewis, 1980;Stace, 1987).…”