FECUNDITY, SPORE RECRUITMENT AND SIZE IN GELIDIUM-SESQUIPEDALE (GELIDIALES, RHODOPHYTA)

Gelidium sesquipedale fecundity was quantified by counting tetrasporan gial sori and cystocarps per meter squared and by estimating the numbe r of spores contained inside them. These were obtained by regression o n a size metric of reproductive structures. Tetrasporangial sori lengt h and cystocarp thickness were the best estimators of spore number. To assess spore recruitment, 12 pottery tiles were fixed to the bottom, and the appearance of small fronds was monitored. No clear seasonal pa ttern of reproduction was found. Tetraspore production peaked in March 1990 with 10.4 x 10(6) spores m(-2), whereas the carpospore peak was lower, 4.9 x 10(5) spores m(-2) in July 1989. Recruitment followed tet raspore peaks. The probability of a G. sesquipedale tetraspore making the transition to a recruit was 4.7 x 10(-5). Frond length was signifi cantly related to tetrasporangial sori number, while cystocarp number was only related to frond branching order. Minimum size for reproducti on was 6.9 cm for gametophytes and 5.4 cm for tetrasporophytes; very r arely were cystocarpic fronds smaller than 9 cm, while tetrasporic fro nds were often longer than 15 cm. Cystocarpic fronds were significantl y shorter and had more branches than tetrasporic fronds.