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PHYCOLOGICAL SOCIETY OF AMERICA

P O S T E L S I A

taxonomy morphology chemistry life history ecology

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DISPERSAL PATTERNS

Postelsia is an annual, exhibiting yearly changes in recruitment patterns. It is in many ways characteristic of a fugitive species, as it will occur only where space is availible and grow rapidly to maintain this position. The larger sporophyte generation becomes visible around February, and a peak in population abundance is generally reached between July and August. When released, non-motile spores drip down Postelsia's blades/sporophylls and generally land anywhere from 1-3 meters of the base of the kelp. This creates a short dispersal range; if spores land any further than this, the probability that the gametophytes into which they develop will be be within range of each other to allow for fertilization will be greatly reduced. As such, Postelsia is often found living in dense aggregations rather than isolation.

Long range dispersal could potentially occur if a sporophyte were ripped from its holdfast prior to releasing its spores. This sporophyte would then have to land in an environment further downshore and release its spores here. Environments in which such dispersal would be most effective would include those experiencing constant wave shock and frequent disturbance with some exposed patches of bare rock.

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