B6 - dispersal and immigration Flashcards
When is dispersal relevant in biogeography?
When it results in immigration, that is movement of individuals to a site not already occupied by that species
What is migration?
The seasonal movement of animals between summer and winter ranges
What is vagrancy?
The random, unpridictable movement of one or a few individuals
Which three criteria must individuals of a species meet in order for range expansions to occur?
1) Travel to a new area
2) withstand often unfavorable conditions during passage
3) establish a viable pupolation upon arrival
What are the three categories of range-expanding dispersal?
1) Jump dispersal: long distance dispersal by movement of individuals within a short timespan
2) Diffusion: slower, through generatons of spread from the margins of the previous range
3) Secular migration: expansion occuring over many generations, giving time for evolutionary change
Explain phoresy
When small animals are transported over large distances by other animals. ex: parasites by hosts
What is exozoochory?
When plant propagules are dispersed via mobile animals, through external tissues (ex: sticking to hair)
What is endozoochory?
When plant propagules are dispersed via mobile animals internally, going through the digestive system
What are the three different kinds of dispersal routes and their effects on biotic exchange?
Corridors: a dispersal route that permits the movement of many or most species of a particular taxon between one region and another. The environment of the corridor is similar to the two source areas
Filters: A dispersal route more restrictive than a corridor, by selectively blocking some individuals. an exampel is the arabian subcontinent (harsh filter) as a filter between northern africa and central asia.
Sweepstakes route: barriers that must be crossed by rare, chance interchanges (ex. iguanas on vegetation raft after storm)
