Reproduction and morphological variation in Southern California populations of the lower intertidal kelp Egregia menziesii (Laminariales)

摘要

Intertidal Egregia menziesii (Turner) Aresch. populations were studied at three Southern California sites to determine temporal and spatial patterns of reproduction and morphology. The timing of sporophyll production and sporophyte recruitment was similar at all sites. Sporophyll production was much greater during winter periods of colder seawater temperatures and shorter day lengths. Sporophyte recruitment occurred from spring through midsummer, similar to 5 months following maximal sporophyll production. Lateral blade morphologies varied in a consistent manner, suggesting a developmental mechanism for form variation in Egregia thalli. Spatulate blades dominated shorter axes and the bases of longer axes, whereas filiform laterals became abundant toward the tips of longer axes. Filiform laterals (9.8 mg O-2.g(-1).h(-1)) had higher light-saturated net photosynthetic rates than spatulate laterals (6.8 mg O-2.g(-1).h(-1)), resulting in a 12% increase in the productivity of Egregia per meter of filiform frond.