Adaptive Radiations Flashcards
What is adaptive radiation?
The evolution of several new species from a single ancestral species within a relatively short amount of time in a localised geographic area.
Follows the peripatric model of speciation
What is adaptive radiation associated with?
Vacant ecological niches
Correlated with geological events e.g. creation of Hawaii
How can ecological isolation occur?
Wide range of growth forms (plants, smilax)
Pollinator / breeding relationships (co-evolution)
New feeding and mating rituals
Reproductive isolation
Occurs near the limits of range
What are the affects of adaptive radiation
Increased disharmony (increased foreign species)
Examples of adaptive radiation on Hawaii
Silverswords Drosophilidae Honeycreepers Cranesbills Bidens
Why does hawaii have so many variations on fruit flies?
511 endemic drosophilids, in one single clade
Speciation by chromosomal rearrangements
Occured during one colonisation event (youngest island)
What adaptations have evolved in the new species of Drosophilids
Shifts to decaying stems, bark and tree sap
Ancestrally: monophagy, oviposition, larval development on decaying leaves.
What patterns can be seen by the drosophiloid area cladogram?
Older species are found on older islands
Newer species appear on newer islands.
What are the patterns with the hawaiian honeycreepers?
33 extant and 14 extinct species
Differing bill morphologies to account for different niches.
How have honeycreepers colonised Hawaii?
Repeated inter-island colonisation –> allopatric differentiation
Followed by sympatric reinfrocement and ecological divergence due to lack of competition and large amount of niches
Define allopatric
separate non-overlapping geographical areas
What similarities are there between tarweed and silverswords?
Shrubby, sprawling plants, similar flower morphology and anatomy.
Fruits which dont float, too thin to survive bird gut, too heavy for wind
Sticky sepals which attach to birds
What patterns are there in silversword speciation?
Moved from west to east towards younger islands.
Grows in lots of different environments.
What physiological and morphological divergences which have occurred in silverswords
Different tissue and elastic properties
Different cell structures for wet (thin cuticle and leaves) and dry (thick) environments
Different veination
What is the silversword rate of divergence like?
0.56 +/- 0.17 species every million years.
Faster than angiosperms, rodents, mammals.
Likely to be fast early radiation which slows due to the filling and creation of niches.
