O S T E L S I A
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.
copyright 1999 sarah oehm
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