Age-specific and season-specific mollusk damage to seedlings of grassland Asteraceae

Abstract

SCHEIDEL, U. AND H. BRUELHEIDE (Albrecht-von-Haller-Institute for Plant Sciences, Department of Ecology and Ecosystem Research, University of Goettingen, Untere Karspiiele 2, D-37073 Goettingen, Germany) Age-specific and season-specific mollusk damage to seedlings of grassland Asteraceae. J. Torrey Bot. Soc. 131:14-0149. 2004.-With the aim of testing the effects of seedling age on the damage caused by mollusk herbivores in the Asteraceae species Centaurea pseudophrygia, C. jacea and Arnica montana, seedlings of five age classes (one to five weeks old) were transplanted into a lowland meadow. Leaf damage and seedling mortality were monitored for about six weeks. For both Centaurea species, age-specific herbivore damage was detected. The majority of the smallest plants were killed within a few days; whereas most of the oldest plants survived until the end of the experiments. Although the oldest plants with the largest leaf area suffered the highest absolute leaf area loss due to mollusk consumption, the mean relative leaf area that was eaten decreased with increasing age when plants were first exposed to herbivores. There were no seasonal differences in the herbivory damage between C. pseudophrygia plants sown and transplanted in spring or late summer. The comparison between seedlings of the montane C. pseudophrygia and the closely related, widely distributed C. jacea revealed similar growth patterns and nearly the same damage, and therefore gave no indication that the lower altitudinal distribution limit of C. pseudophrygia may be caused by a more severe seedling herbivory. In contrast to Centaurea, the highly palatable Arnica montana seedlings were completely consumed within a few days after transplantation, irrespective of age class and without any regeneration events, supporting previous hypotheses that mollusk herbivory is a limiting factor for the geographical range of Arnica montana. In general, the results confirm that a high sampling resolution in time is of great importance to detect age-specific mortality factors in plant population studies.