Environmental determination of shoot height in populations of the cordgrassSpartina maritima

• Published in: Estuaries 2005-10, Vol.28 (5), p.761-766
• Main Authors: Castillo, J. M., Redondo, S., Wharmby, C., Figueroa, M. E., Luque, T., Castellanos, E. M., Davy, A. J.
• Format: Article
• Language: English
• Subjects: Aeration; Aquatic plants; Estuaries; Gas exchange; Genotype & phenotype; Growth; Habitats; Height; Hypoxia; Natural populations; Phenotypes; Phenotypic plasticity; Photosynthesis; Plant growth; Plastic properties; Plasticity; Population genetics; Populations; Redox potential; Rhizomes; Salt marshes; Saltmarshes; Sediment; Sediments; Shoots; Transplantation; Turnover time
• ISSN: 0160-8347; 1559-2723; 1559-2731
• DOI: 10.1007/BF02732913

Spartina species tend to exhibit a range of phenotypes, often with short and tall growth forms. Such differences have been attributed variously to environmentally induced phenotypic plasticity and genetic diferentiation between populations. This work examines the basis of height variation inSpartina maritima (Curtis) Fernald at Odiel salt marshes, southwest Spain. Populations from sites with lower sediment redox potentials tended to have significantly taller shoots. Thirty-four natural populations with an 8-fold range of shoot height were transplanted to a common environment on an unvegetated, intertidal plain and shoot height was measured annually for 3 yr. There was a striking convergence in height across populations after transplantation and the change in height in each year of a population was linearly related to its initial height. Most populations grew taller after transplantation, suggesting environmental limitation in their natural habitats. Populations that were originally tall tended to become shorter. The change in shoot height was negatively related to the difference in surface sediment redox potential between their natural sites and the common transplant site. Hypoxic sediments may stimulate stem growth, resulting in improved photosynthetic gas exchange and internal aeration of roots and rhizomes. Although height variation inS. maritima appears mainly to be a result of phenotypic plasticity, a genetic component cannot be ruled out. This study emphasizes the importance of long-term studies, preferably longer than turnover time of shoot populations. The highly plastic growth form ofS. maritima allows it to colonize a wide range of habitats in environmentally heterogeneous salt marshes.