COST OF REPRODUCTION IN FUCUS-DISTICHUS

Reproductive effort (ratio of fertile to total plant dry weight) was measured in Fucus distichus L. emend. Powell. On average, 12.7 % of plant dry weight is in reproductive biomass and this amount is relatively constant over most months. Reproductive effort does not vary among plants of different sizes and dry weights. However, fertile plants are significantly (p < 0.05) bigger than the non-fertile plants, and have a better survival rate. There is no clear indication of cost of reproduction with respect to the longevity of fertile vs non-fertile plants. Fertile plants, especially those > 17 cm in length, tend to exhibit negative or zero growth much more often than non-fertile plants, suggesting that the cost of reproduction may be manifested in the form of reduced growth, rather than in greater mortality or shorter longevity of the fertile plants. The failure to detect cost of reproduction with respect to mortality and longevity may be due to the modular nature of the plants, where cost occurs at the level of the modules (branches) rather than at the level of the whole plant.