ENVS10001 Lecture Notes - Lecture 15: Biogeography, Endemism, Gigantism
17 May 2018
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Department
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Professor
• Characteristics of floristic realms + biomes represented beneath ground in soil
ISLAND BIOGEOGRAPHY
• Ecological Islands: isolated remnants or elevated masses
How do patterns influence biota of islands?
• Distance to source of propagules (plant material used for the purpose of reproduction)\
• Location, size, age (opportunity for immigrants, + soil) + environmental conditions (substrate
available for successful establishment?)
Dispersal
• Dispersal mechanisms: wind + gravity, being eaten or by water (float)
• Ability to disperse influences:
o Chance of immigration
o Chance of repeated introduction
o Endemism – lesser if higher diversity
Theory of Island Biogeography
• Immigration: new habitats will receive surge of immigrants, establishment + reproduction
o Influenced by: distance to source, area of island + time
• Extinction + Emigration: inevitable, may be a result of: evolution into other species, natural
disaster or competition for resources
o Influenced by time, area + number of species
• Distance effects: nearer islands = more diverse
• More isolated ‘islands’ = fewer species
• Area effects ! large islands more species than smaller islands
o Distinct correlation between high numbers of species +
large areas
• Species Richness:
o Lower on islands than mainland’s
o Higher endemism + high specialisation
o Finish
• Gigantism: due to lack of competition, abundant resources
• Mini-species: due to lack of resources + competition
Applications of Biogeography
• To manage: must consider extinction, immigration + outside
influences
• Habitat Islands: caves, top of mountains, lakes
• Management rules: reserve design
• Strategy that maximises diversity may not maximise the probability
that the most threatened species survives
Islands
•Continental: affinities to mainland, fertile, water + often more diverse as compared to below
•New Volcanic: origins from tectonic activity, little: soil, water + diversity
•Coral Atolls: built on submerged land surface, high disturbance, poor/little groundwater, poor
nutrients + low elevation
Document Summary
Characteristics of floristic realms + biomes represented beneath ground in soil. How do patterns influence biota of islands: distance to source of propagules (plant material used for the purpose of reproduction), location, size, age (opportunity for immigrants, + soil) + environmental conditions (substrate available for successful establishment?) Dispersal: dispersal mechanisms: wind + gravity, being eaten or by water (float, ability to disperse influences, chance of immigration, chance of repeated introduction, endemism lesser if higher diversity. Immigration: new habitats will receive surge of immigrants, establishment + reproduction. Influenced by: distance to source, area of island + time: extinction + emigration: inevitable, may be a result of: evolution into other species, natural disaster or competition for resources. Applications of biogeography: to manage: must consider extinction, immigration + outside influences, habitat islands: caves, top of mountains, lakes, management rules: reserve design, strategy that maximises diversity may not maximise the probability that the most threatened species survives.
