Helsinki Stickleback Group

Effects of eutrophication on sexual selection

The effects of eutrophication on sexual selection and population viability in sticklebacks

The aim of the project is to investigate the effects of eutrophication and increased growth of filamentous algae on sexual and viability selection in a common littoral fish, the three-spined stickleback Gasterosteus aculeatus. Sexual selection is one of the main forces of evolution and gives rise to the evolution of characters that increase mating and fertilisation success. It is opposed by viability selection and its intensity varies in time and space depending on environmental heterogeneity. Thus, while equilibrium between sexual and viability selection may be achieved in one environment, changes in conditions can change the relative intensity of the selection pressures and decrease the fitness of the population. Despite these obvious connections between the habitat, selection and population viability, the effects of environmental changes on sexual selection and the consequences this may have for populations, species and ecosystems are poorly understood.            

Eutrophication is a serious environmental problem along the coasts of Europe, with notorious effects in the Baltic Sea. It alters the species composition of benthic communities by increasing the growth of filamentous algae at the expense of slow-growing macro algae. This changes the littoral fauna, but the long-term effects are unknown. Recent research has revealed that the cost of mate choice increases with increased algae growth, and that the variation in reproductive success among stickleback males decreases. These results suggest that eutrophication decreases the intensity of sexual selection. Here, the aim is to follow up this study and investigate the effects of increased growth of filamentous algae on sexual and viability selection. The work is divided into four parts:

• Effects of eutrophication on sexual selection and juvenile viability
• Adaptive or non-adaptive changes in sexual selection in response to eutrophication?
• Evolutionary changes or plastic responses to eutrophication?
• Effects of eutrophication on inbreeding and population viability.

The work will be realised through field monitoring and field and laboratory experiments, selection experiments, relocation of individuals, inbred selection lines, as well as IBM modeling techniques.             

The outlined research will give new information on the effects of habitat changes on the selection processes that drive adaptation and evolutionary changes. This would be of importance in conservation work, in predicting the long-term effects of habitat changes on species and ecosystems, and in the planning of how to prevent large-scale changes. In addition, the work would contribute to the ongoing debate over whether sexual selection increases or decreases population fitness and its role in the extinction of populations and species.

Publications

• Candolin, U. & Salesto, T. 2006. The effects of vegetation cover on
  nesting behaviour of sticklebacks. – Behavioral Ecology and Sociobiology,
  59, 689-693.
• Wong, B.B.M. & Candolin, U. 2005. How is female mate choice affected by
  male competition? – Biological Reviews 80, 559-571.
• Candolin, U. 2004. Effects of algae cover on egg acquisition in male three-spined stickleback. – Behaviour 141, 1389-1399
• Candolin, U. & Voigt, H.-R. 2001. Correlation between male size and territory quality: consequence of male competition or predation risk? – Oikos 95,225-230.