Phenotypic plasticity and population differentiation in Suaeda maritima on a salt marsh

Suaeda maritima (L) Dumort is a polymorphic annual species of the family Chenopodiaceae that in the UK occurs exclusively in coastal salt marshes. The main aim of this study has been to examine the phenotypic variations within and between its populations in the heterogeneous microenvironments of a salt marsh. Detailed field characterizations of the growth, seed production and seed heteromorphism of four Suaeda maritima populations at Stiffkey salt marsh were conducted over three consecutive years, revealing considerable consistent phenotypic variation between populations on the high marsh, high-marsh creek bank, upper low marsh, and low marsh. Field environmental heterogeneity was assessed by taking measurements of sediment salinity, water content, organic content, redox potential, elevation in the tidal frame and annual number of tidal inundations. They demonstrated that different Suaeda maritima populations do indeed experience divergences between their environments that could both affect the phenotypic responses of developing plants and constitute selection pressures for the evolution of genetically differentiated populations. Experiments involving seedling reciprocal transplantation in the field and seedling transplantation to uniform laboratory conditions revealed significant differences among populations in terms of survival, growth and fecundity parameters. Detailed experiments examining the effect of salinity, temperature, light and storage conditions on seed germination and dormancy also revealed seed dimorphism and significant variation in the germination behaviour among populations. Suaeda maritima populations exhibited substantial evidence of genetic differentiation (reflecting the complex heterogeneity in their natural microhabitats) and, therefore, it can be suggested that this differentiation reflects adaptive ability to colonize wider range of habitats along the environmental gradients. Key words: Suaeda maritima, Salt marsh, Microhabitat, Population differentiation, Phenotypic plasticity, Fecundity, Seed heteromorphism, Dormancy, Germination, Survival, Reciprocal transplantation, Spatial heterogeneity

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of East Anglia

Year dc:date.issued

2012

Author dc:creator

• Alghamdi, Ahmed

Language dc:language

en