Flowering does not decrease vegetative competitiveness of Lolium perenne

• Published in: Basic and applied ecology 2009-07, Vol.10 (4), p.340-348
• Main Authors: Thiele, Jan, Jørgensen, Rikke B., Hauser, Thure P.
• Format: Article
• Language: English
• Subjects: Allocation trade-off; Bet-hedging; Clonal propagation; Costs of sexual reproduction; cultivars; flowering; Forage productivity; growing season; Invasion; life history; Lolium perenne; Plant breeding; plant competition; plant reproduction; sexual reproduction; Turf grass; turf grasses; vegetative propagation; Vernalisation; vernalization
• ISSN: 1439-1791
• DOI: 10.1016/j.baae.2008.04.002

The theory of life-history evolution commonly assumes a trade-off between sexual and vegetative reproduction. Hence, production of flowers and fruits should have measurable costs in terms of reduced vegetative growth. This trade-off may be meaningful for breeding of forage and turf grasses as reduced flowering could free resources and increase productivity. But if so, less-flowering cultivars might be more competitive and invade natural swards. We tested for costs of sexual reproduction on vegetative propagation and competitiveness of the perennial grass Lolium perenne, one of the most important forage and turf grasses worldwide. We used the differences in vernalisation requirement between northern and southern European provenances to manipulate the degree of flowering. Over three growing seasons, we counted the number of flower stems and measured the clone diameter. The vernalisation treatments were successful in producing clones with largely differing degrees of flowering. However, we found no negative correlation between flowering and vegetative propagation and competitiveness. Early and strongly flowering southern provenances showed less clonal growth and higher mortality, but within provenances the response of clone diameter to flowering was positive or neutral. We conclude that investment of resources into flowering has no measurable costs on vegetative propagation and competitiveness of L. perenne. The apparent lack of costs of sexual reproduction could be explained by bet-hedging strategy that is focused on survival and growth rather than reproductive effort in order to maximise the life-time fitness. In der Theorie der Evolutionsbiologie wird gemeinhin ein Trade-off zwischen sexueller und vegetativer Reproduktion vermutet. Demzufolge sollte die Produktion von Blüten und Früchten messbare Kosten in Form von reduziertem vegetativen Wachstum haben. Dieser Trade-off könnte von Bedeutung für die Züchtung von Futter- und Rasengräsern sein, da verringertes Blühen Ressourcen freisetzen und die Produktivität erhöhen könnte. Aber wenn dem so ist, könnten die weniger blühenden Zuchtformen erhöhte Konkurrenzkraft besitzen und natürliche Grasbestände invadieren. Wir haben die Kosten sexueller Reproduktion für die vegetative Ausbreitung und die Konkurrenzstärke des ausdauernden Wirtschaftsgrases Lolium perenne untersucht. Dabei haben wir die unterschiedlichen Vernalisierungsansprüche nord- und südeuropäischer Provenienzen genutzt, um die Blühintensität zu manip