UBC Theses and Dissertations
Ecological differences between the isomorphic phases of Mazzaella lilacina (Rhodophyta, Gigartinaceae) Phillips, Brent
Some of the potential factors responsible for the observed increase in the proportion of tetrasporophytes in wave exposed populations of Mazzaella lilacina (Postels et Ruprecht) Leister have been examined. By counting the number of spores per reproductive structure tetrasporophytes were found to hold significantly more spores than gametophytes in August, 1990. Only slightly more tetraspores than carposspores were found at other sampling time (p=0.127 and 0.637). As expected, based on the production of spores, the proportion of gametophytes among recruits into intertidal clearings was high , although not as high in the exposed site as was expected based on the proportion of reproductive tetrasporophytes in the population at the time the clearings were made suggesting that tetrasporophyte recruitment is somehow favoured. The opposite was observed in the sheltered site suggesting that gametophyte recruitment is favoured in that site. Monitoring of blades following recruitment showed a slight trend towards a decreasing proportion of gametophytes in the exposed site and an increasing proportion of gametophytes in the sheltered site, suggesting that the mortality of on phase was higher than the other in each site. Finally, thalli of M^ lilacina were pulled and broken in the field . Force to break and surface area data was used to generate curves showing the proportion of each phase which would be broken with water moving at velocities from 0 to 20 m/s. Gametophyte blades longer than 15cm in the exposed site were significantly more susceptible to removal by moving water than were tetrasporophyte blades.