Spatio-temporal variation in fruit production and seed predation in a perennial herb influenced by habitat quality and population size
Article first published online: 11 JAN 2008
© 2008 The Authors
Journal of Ecology
Volume 96, Issue 2, pages 334–345, March 2008
How to Cite
Ågren, J., Ehrlén, J. and Solbreck, C. (2008), Spatio-temporal variation in fruit production and seed predation in a perennial herb influenced by habitat quality and population size. Journal of Ecology, 96: 334–345. doi: 10.1111/j.1365-2745.2007.01334.x
- Issue published online: 11 JAN 2008
- Article first published online: 11 JAN 2008
- Received 18 November 2006; accepted 29 October 2007 Handling Editor: Peter Klinkhamer
- flower production;
- fruit production;
- habitat quality;
- pollen limitation;
- population density;
- population size;
- resource limitation;
- Vincetoxicum hirundinaria
- 1In patchily distributed plant species, seed production is likely to be influenced both by local abiotic factors affecting plant size and conditions for fruit maturation, and by population characteristics affecting the intensity of interactions with mutualists and antagonists. However, the relative importance of these effects is poorly known.
- 2We used multiple regression and path models to examine the importance of abiotic factors (sun exposure, soil depth) and population characteristics (size, density and connectivity) for variation in flower and fruit production and intensity of seed predation among 39 populations of the long-lived herb Vincetoxicum hirundinaria in three consecutive years. In addition, we manipulated water availability in a field experiment and recorded short-term and long-term effects on fruit output, and conducted a supplemental hand-pollination experiment.
- 3Flower production varied little, while fruit initiation, fruit abortion and fruit predation varied considerably among years. Sun exposure and soil depth affected fruit production per plant indirectly and positively through their effects on flower number. Population density affected fruit production negatively through its effect on flower number. Both fruit initiation and the proportion of fruits attacked by the tephritid fly Euphranta connexa were related positively to population size.
- 4The number of full-size fruits per plant was related positively to sun exposure and population size in two years each, and related negatively to population density in one year. However, because of seed predation, the number of intact mature fruits was related significantly to population characteristics in only one of three years.
- 5The field experiments showed that both shortage of water and insufficient pollination may limit fruit set in V. hirundinaria.
- 6Synthesis. These results demonstrate that the relative importance of local abiotic conditions and population characteristics may vary considerably along the chain of events from flower formation to intact fruit, and also among years. They further show that, at least in species with a naturally patchy distribution, connectivity may be relatively unimportant for variation in reproductive output compared to effects of habitat quality, population size and density.