Island Biography

Island Biography

1. speciation seperating of two sub groups of a species by reproductive isolation

   • 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
   • allopatric speciation - isolation due to geographical changes and barriers
     • this can be due to alter sealevels glaciaers, earth quakes any sort of natural changes 
     • changes in genotypic or/and phenotypic divergence
       • -they become subject to different selective pressures  - undergo genetic drift (independently)  - different mutations arise 
       • cant interbreed if the barrier is removed
         • Interbreeding within subgroups + mutations - Interbreeding between subgroups = two new species or populations 
   • Sympatric speciation - changes in mate selection due to behaviour or gentic change
     • mating is no longer random causing genetic difrt between the two populations - two populations with out barriers

2. very early on its been noted islands have a lower biodiversity with bigger islands having more then lower ones

   • there is a thing called the island effect - islands are therefore more of a conept of major isolation
     • 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 
     • theory of island biology was devised
       • habitat diverstiy
         • the bigger the island the more hibtats are avialable so more organisms can use them
         • early work was done on birds but there high dispersal rate wasnt taken into acount
       • equilibrium theory - MacArthur and Wilson 1967
         • 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 
         • evolutionary aproach
         • Immigration - a key processes
           • 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 
           • dispersal rate
             • 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
             • Holloway, 1977
         • extinctions rate
           • 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 
         • • 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 
           • tonn and magnusome 1982
             • fish in the westconsen lake 
           • simbulof and willson
         • location
           • 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 
         • effected by many different factors
           • size of the unit of habitat
           • variety of niches or micro-habitats available
           • distance to source-pool of species

3. METAPOPULATIONS

   • 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 

4. applied in the marine sector

   • much less studies, larva; and propagule exchange
     • 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 
   • Mussels
     • these mussel beds can be used to study all aspects that are effected by islances - like parameters and size and stress, location and age 

5. Conservation

   • is it better to have one big protected are or many small protected area - this is still an on going debate 
   • heterogenity plays a part in conservation areas
   • is it better to look after the main animals
   • Banks Et al 2005

Imagens e arquivos do mapa