Which demographic traits determine population growth in the invasive brown seaweed Sargassum muticum?
Article first published online: 23 APR 2009
© 2009 The Authors. Journal compilation © 2009 British Ecological Society
Journal of Ecology
Volume 97, Issue 4, pages 675–684, July 2009
How to Cite
Engelen, A. and Santos, R. (2009), Which demographic traits determine population growth in the invasive brown seaweed Sargassum muticum?. Journal of Ecology, 97: 675–684. doi: 10.1111/j.1365-2745.2009.01501.x
- Issue published online: 16 JUN 2009
- Article first published online: 23 APR 2009
- Received 18 June 2008; accepted 9 March 2009Handling Editor: Christer Nilsson
- biological invasion;
- Cystoseira humilis;
- life-history traits;
- matrix models;
- population dynamics;
- population growth;
- Sargassum muticum;
- 1Life-history traits commonly associated with plant invasiveness are vegetative reproduction or r-selected traits such as short generation times and high rates of reproduction and individual growth.
- 2We used matrix modelling to assess which demographic traits are important for the population growth of an invasive seaweed lacking vegetative reproduction and whether demographic and life-history strategies shift with increased dominance of the invader. The vital rates of one of the most successful invading seaweeds, Sargassum muticum, were investigated monthly for 2 years in intertidal pools dominated by the native brown seaweed Cystoseira humilis and by S. muticum, respectively. In order to speculate about the demographic mechanisms that determine invasiveness of S. muticum, and as the study sites were recently colonized, we assumed that C. humilis and S. muticum pools are proxies for early and late phases of invasion, respectively.
- 3Both deterministic and stochastic matrix models showed positive rates of population growth, and rates were significantly higher in the pools dominated by S. muticum than in the ones dominated by C. humilis, indicating demographic changes with invader dominance. The variability of population growth rates and of reproductive and elasticity values of S. muticum was higher in the pools dominated by C. humilis, suggesting invader-driven stabilization of environmental conditions. Generation times of the species increased with invader dominance, supporting invader-stabilized environmental conditions.
- 4Elasticity analyses revealed that the most important demographic trait for population growth rate at both levels of invader dominance was the persistence of the non-fertile adult fronds rather than reproduction or growth. No major shifts in the life-history strategy of S. muticum between levels of invader dominance were detected.
- 5Synthesis. This study suggests that the invasiveness of S. muticum, a perennial invader without vegetative reproduction, relies on K- rather than r-selected traits and without drastic changes in life-history strategy between phases of invasion.