BIOL1003 Lecture Notes - Lecture 21: Parasitism, Commensalism, Acer Saccharum

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Diversity- factors which cause biodiversity
Factors that drive biodiversity
Island biogeography
Competition
Competitive exclusion
Dominant versus keystone species
Disturbance
Interactions drive diversity
Biodiversity is primarily defined as the number of species present
The number of species is limited by the number of available niches
Niches are limited by interactions with the environment and other species (e.g.
realised niche)
Evolutionary consequences of competitive interactions can result in competitive
exclusion:
oOne species becomes extinct
oDivision of niche takes place
Alfred Russel Wallace
Darwin and Wallace shared similar ideas at the same time
Wallace’s line- primate (Indonesia) vs marsupials (Australia), definitive separation
between the animals you find on either side of the line
Island Equilibrium theory of biogeography
Species diversity on “islands” will represent a dynamic balance between the
probability of successful colonisation by new immigrant species, and extinction of
existing resident species
Island
biogeography
E.g. agricultural islands, suburban islands, fields,
lakes, cities
Design of conservation reserves: the SLOSS debate
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Larger better to conserve species
Edges are good for predators but detrimental
for prey
Competitive exclusion
A competitive advantage, will eventuate in
success and extinction of the other species
(can be on a local scale)
Colobus monkeys- blank and white at the top
of the forest branches whereas the red ones are in the middle- separation of a niche
Antechinus swainsonii is more tree dwelling and antechinus agilis is more ground
dwelling
Specialists vs generalists
Specialists are ecologically more efficient than generalists at the cost of having a
move restricted fundamental niche
When ample resources are available, specialists will usually out-
compete generalists
Specialists tend to be spaced out more evenly along axes of resource
distribution
Specialists are less resilient to change (disturbance) than generalists
Evolutionary time and competition is required for
specialisation
E.g. birds
oSanderling- general predator, eats anything
oAvocet- specialist, filters through shallow water
oCurlew- uses like shovel to get at the sand
underneath
oSpoon-billed sandpiper
oWrybill- eats snails by twisting into shells
oAll eat similar prey but have very divergent beak
shapes- more specialised beak shapes
Example of competitive exclusion
Barnacles- balanus would outcompete the other species
when they are present as they do better in the intertidal
zone
Antichinus- different habitats of organisms with different
number of teats
Squirrels- red native to U.K. and grey native to America,
grey was introduced to the U.K. and is outcompeting the
red, however the pine marten has begun to prey on the
grey squirrel over the red ones because they are larger,
less agile, and not used to the environment
Coping with disturbance
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Document Summary

Biodiversity is primarily defined as the number of species present. The number of species is limited by the number of available niches. Niches are limited by interactions with the environment and other species (e. g. realised niche) Evolutionary consequences of competitive interactions can result in competitive exclusion: one species becomes extinct, division of niche takes place. Darwin and wallace shared similar ideas at the same time. Wallace"s line- primate (indonesia) vs marsupials (australia), definitive separation between the animals you find on either side of the line. Species diversity on islands will represent a dynamic balance between the probability of successful colonisation by new immigrant species, and extinction of existing resident species. E. g. agricultural islands, suburban islands, fields, lakes, cities. Edges are good for predators but detrimental for prey. A competitive advantage, will eventuate in success and extinction of the other species (can be on a local scale)

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