Lecture 2 Adaptive Radiation Flashcards
communities assemble overtime, what are the two important processes that achieve this?
1) dispersal from other localities
2) evolution of new species
such as Galapogos archipelago
What is a definition for adaptive radiation?
“the diversification of a lineage into species that exploit a variety of different resource types and differ in morphological and/or physiological (phenotypic) traits used to exploit these resources” (Schluter, 1996)
OR- briefly - speciation associated with ecological diversification from a common ancestor
Give an example of adaptive radiation:
Gelapogos Finches
Endemic to galapogos & 1 near island
where can we find evidence of adaptive radiation?
fossil records in:
reptiles & aves
mammals
Such cases involve radiation in the production of regional or global species pools
But adaptive radiation can also be important directly in the assembly of local communities, particularly in isolate communities
why could adaptive radiation be responsible for most species we see in isolated communities?
because isolated communities are difficult to colonize
what does the term anadromous mean?
a marine fish that migrates and reproduces in freshwater e.g.
salmon
3 spined stickleback
give the case study for rapid adaptive radiation
3 spined sticklebacks are found in landlocked freshwater lakes. some have predators such as bass and some don’t. Sticklebacks in Lakes with pradators have more bony scales and the sticklebacks in lakes without predators have less armour, no need to waste energy on that. (Schluter, 1996)
how did the isolated lakes in british Columbia, canada form?
Once covered in 2Km of ice around 13,000yrs ago. As ice melted, the depressed land (due to heavy ice) rebounded allowing isolated lakes to form. This is known as isostatic change.
what is isostatic sea level change?
a local sea level change.
provide another stickleback case study for adaptive radiation
2 distinct morphs found in 6 lakes.
Benthic - big fat, bull-doses its way through the sediment and is built for this
Limnetic - thin and small, feed on plankton.
are they both fitter in their own environment?
set up tanks to show this. growth aren’t used as a measurement of fitness. both growth rates were better on their own environment. is adaptive.
they will breed in their own pairs, but can hybridise if not given the choice. hybrids were worse in both tanks, so selected against (Schluter, 1996)
Famous/most striking example of adaptive radiation:
Cichlid fish!
they occupy many niches in lakes.
Malawi flock (660-1,000+ spp.)
0.7-2 mya- 1-2 colonizing lineages (Turner, 2000.)
What is convergent evolution:
Where organisms not closely related (not monophyletic), independently evolve similar traits as a result of having to adapt to similar environments or ecological niches.
This has happened with cichlid fish in different lakes! (Turner, 2000)
