1 Colonization of a site: dispersal adaptations requirements sequence r and K strategy Consequences More examples Dispersal and colonization of habitats Example Location: present Indonesia, island of Krakatoa The explosion destroyed completely life on the volcano and adjacent islands. A new cone formed and its ecological development was monitored, with decent ecological surveys made as early as 1897. The 1883 eruption ejected more than 25 cubic kilometers of rock, ash, and pumice Example Only fraction of the surface is alive … Colonization and development of communities was interrupted several times
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1
Colonization of a site:
dispersal adaptations
requirements
sequence
r and K strategy
Consequences
More examples
Dispersal and colonization of habitats
Example
Location: present
Indonesia, island of
Krakatoa
The explosion destroyed completely life on the volcano and adjacent
islands.
A new cone formed and its ecological development was monitored, with
decent ecological surveys made as early as 1897.
The 1883 eruption
ejected more than 25
cubic kilometers of
rock, ash, and pumice
Example
Only fraction of
the surface is
alive …
Colonization
and
development of
communities
was interrupted
several times
2
Krakatoa (Krakatau) – dispersal types
After Whittaker et al. 1997
Ridley„s dispersal classification on the then known floras on
Krakatau (up to 1919 only), Christmas Island and Cocos-
Keeling
Dispersal type Krakatau
Christmas Cocos
Sea borne 60 44 17
Wind 34 9 0
Berry or drupe 34 36 0
Adhesive 9 15 5
Mud on birds 3 0 0
Doubtful 4 7 0
Total 144 129 22
Pteridophyta 48 25 0
Timing
Hawaii (more isolated):
• one plant species every 30 000 years,
• one land snail every 200 000 years and
• one bird species every 350000 years These estimates are based on the average age of the
K = carrying capacity (~max N). Thus, if there is a limit:
Invading plants grow quickly, and make lots of seeds ( “r” strategists). “K” strategists focusing their energy and resources on growth and long-term survival (usually come in later in the settlement of new habitat).
From this:
If N is small, a species must grow fast; if N is near K, it should keep it without large fluctuations
Pioneer communities
Mature communities
Dispersal limitation: limitation of distribution or abundance
because of either constraints on dispersal or inadequate
production of dispersing individuals.
Recruitment limitation: limitation of distribution or abundance because
of either constraints on survival of individuals that arrive or were born at
a site (local filter). How would we demonstrate it empirically?
Initial
community
Resultant
community
General concepts
http://www.logos-verlag.de/cgi-bin/buch/isbn/423 Just for fun
Inspection of right-hand lists alerts to the fact that all these phenomena, factors, or constraints depend on the area and time considered (scale-dependence)