L6 Dispersal limitation Flashcards
(15 cards)
define dispersal limitation
when an ecological community is determined and limited by dispersal
what did the Maluku island experiment by MacArthur and Wilson determine
that area of island impacts the number of species on the island, the distance of island from mainland also has an impact (number of species and rate of dispersal)
what does the isolation of an island affect
how easy it is to hit maximum number of species on island
what does the size of an island affect
maximum diversity
what are the three processes that occur on an island that dictate the number of species
immigration, speciation and extirpation (only bigger islands have speciation)
what is the calculation for number of species on an island using extirpation and immigration
- immigration (I) = number of total species * rate of immigration - S * rate
- extirpation (E) = S * rate of extirpation
- trying to find S when I and are equal
calculate an example of total number of species on an island when immigration rate is 1/5, extirpation rate is 1/4 and total number of species is 12
- I = (12-S)/5 - S/5
- E = S/4
- (12-S)/5 - S/5 = S/4
- 4(12-S) = 5S
- 48 -4S = 5S
- S = 48/9 (5.33)
in what way has the island model been improved to be more accurate?
the closer the island is the higher rate of immigration
what trend can be observed in extirpation on bigger islands?
bigger islands are more resistant to extirpation
what is another variable that is needed to take into account when trying to determine the number of species on an island
stochasticity - the actual number will fluctuate around the equilibrium
what was the defaunation experiment and what did it determine
Simberloff and WIlson 1966 - killing all species on an island with pesticides to understand how the species representation changed, what was able to colonize which island. findings were that some species were more equipped to colonize than others
what are some reasons plants need to disperse
to avoid illnesses, prevent interbreeding and increase fitness, gain more territory
what are some examples of ways that plants disperse? (6)
- gravity - things move past and knock down seeds
- gyration -wind resistance, move well through air especially from tall trees
- animal - by eating, pollinating or by attaching to fur/feet
- wind - light seeds float
- ballistic - when pod touched, seeds shoot out
- water - island adaptation, seeds float when they fall into water
what is specific about the plant arthionema arabicium
it can swithc between strategies of seed dispersal - eg high altitude means it will choose long-distancee seed dispersal (dehiscent)
what is the trend is spatial structure as dispersal syndome increases
cluster size increases (although experiment by plotkin and seidler did not take phylogeny into account, only strategy)
