Island Biography

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• this is caused by constant splitting of genes by mutations and a blockage between the species, meaning they drift apart better known as genetic drift

1. allopatric speciation - isolation due to geographical changes and barriers

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   • this can be due to alter sealevels glaciaers, earth quakes any sort of natural changes 
   1. changes in genotypic or/and phenotypic divergence

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      • -they become subject to different selective pressures  - undergo genetic drift (independently)  - different mutations arise 
      1. cant interbreed if the barrier is removed

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         • Interbreeding within subgroups + mutations - Interbreeding between subgroups = two new species or populations 
2. Sympatric speciation - changes in mate selection due to behaviour or gentic change

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   • mating is no longer random causing genetic difrt between the two populations - two populations with out barriers

1. there is a thing called the island effect - islands are therefore more of a conept of major isolation

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   • oceanic islands are the most obvious as many of the animals are cut off by the ocean matrixs
   • tops of mountains can also be classed as an island due to be cut via differences in properties between the valley below 
   • lakes can also be classed as island as they are marine environments cut off by a land matrix 
   1. theory of island biology was devised
      1. habitat diverstiy
         1. the bigger the island the more hibtats are avialable so more organisms can use them
         2. early work was done on birds but there high dispersal rate wasnt taken into acount
      2. equilibrium theory - MacArthur and Wilson 1967

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         • many things effect the species level of an island the main two are arivals and deaths when these level out there becomes a constant number of species present 
         1. evolutionary aproach
         2. Immigration - a key processes

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            • form the graph attached you can see that when a new island is found there is a increase in the amount of species that can travel there 
            • the bigger the island and the closer the higher the probability of species breeding here 
            2. dispersal rate

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               • many closely related species have very different dispersal rates such as Nucella lapillus and Litterina littorea, this shows that diversity also must be contorled by the idivduals dispersal rates
               1. Holloway, 1977
         3. extinctions rate

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            • as more animals come into the island there is more competition for niches and so forth so weaker animals die out - this is higher on smaller islands due less resources 

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            • the result of this theory is that there is a set turnover rate for each island and its factors  seen within the graph there is a difference in the key number of species 
            1. tonn and magnusome 1982

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               • fish in the westconsen lake 
            2. simbulof and willson
         5. location

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            • location is important such as logitude and latitude, hieght on the shore and environmental stress and is it in the pathway of potential species ir currents and hydrodynamics 
         6. effected by many different factors
            1. size of the unit of habitat
            2. variety of niches or micro-habitats available
            3. distance to source-pool of species

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• This was developed in the late 70s - basically its a group of populations that interact on a certain level - so locals might become extinct but other populations will not be effect
• rescue effect from other populations - source-sink dynamics 

1. much less studies, larva; and propagule exchange

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   • due to the differences between terrestrial and marine habitats this needs more indepth sudy 
   • whats is the link?? what rols does biodiversity play in the functions of an ecosystem 
2. Mussels

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   • these mussel beds can be used to study all aspects that are effected by islances - like parameters and size and stress, location and age 

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• is it better to have one big protected are or many small protected area - this is still an on going debate 

1. heterogenity plays a part in conservation areas
2. is it better to look after the main animals
3. Banks Et al 2005