Lecture 26 Flashcards
(25 cards)
what is coevolution?
two or more species:
* exert selective pressures or each other and evolve in response to each other (these two must happen)
* because each species is evolving in response to the other, one important feature of coevolution is that the selective environment is constantly changing
what is one important feature of coevolutin?
the selective environment is constantly changing
when does coevolution occur?
- selective pressures for coevolution will be strongest when there is a close ecological relationship
- a close ecological relationship means a specialist rather than generalists (get more info)
what can coevolution involve?
either positive or negative interactions that affect the interacting partners differently
what does coevolution need, just like any other type of evolution?
genetic variation and heritable variation
what are the four situations of coevolution?
- predator and prey: positive for predator, negative for prey
- parasites and hosts: positive for parasite, negative for host
- mutalists: positive for both of them
- competitors: negative for both compeititors
how does the strength of reciprocal selection vary?
varies geographically
when can variation be maintained?
when traits have other costs.
what is the “cost of resistance”?
what is meant by coevolutionary arms race?
coevolving species have to constantly improve to meet each new adaptation with a better adaptation of their own, interacting antagonistically and exerting reciproal directional selection
what is coevolutionary escalation?
coadaptations become increasingly powerful, yet species are not any better adaptated because the selective landscape is constantly changing
what is the red queen hypothesis?
running as fast as possible just to stay in the same place.
species (or populations) must continually evolve new adaptations in response to evolutionary changes in other organisms to avoid extinction.
explain the snake coevolutionary arms race.
- snake populations vary in resistant to new toxins
- snake populations outside of the newt toxins range have lower resistance compared to snakes within that range
*
what are coevolutionary hot spots and cold spots?
hotspot: populations where selection is strong on both species
cold spots: populations where selection is weak on one or both species
whether a region is a hotspot or coldspot depends on what?
species abundance, amount of gene flow, presence of other predator/prey, environmental conditions, etc
what do coevolutionary outcomes depend on?
intensity of selection, genetic drift, and gene flow among populations. interactions vary in direction or intensity in different populations
what can geographic mosaics also apply to?
mutalisms
what is some key information about mutualisms?
- positive frequency dependent selection
- they both benefit so it increases in frenquency
the intensity and specificity of coevolutionary interactions can vary ___________ and ______ _____-
geographically and over time
coevolution may involve what that maintains genetic variation?
coevolution interactions may involve frequency dependent selection that maintains genetic variation
what is batesian mimicry?
- harmless species has evolved the capacity to imitate the warning signals of a harmful species
- so harmless species resemble harmful or toxic species, derviving protection from predators (‘cheating’)
- if predators eat non toxic mimic will eventually learn not to avoid real toxic species, which is a cost to the toxic model
- toxic species should evolve away from mimic, the micmic should evolve to catch up wth ut
- most common and stable when the mimic is rarer than the model
when is batesian mimicry the most common and stable?
when mimic is rarer than the true toxic model
what is mullerian mimicry and what does it facilitate?
- it is covergent evolution of unrelated organisms on the same phenotype. involves unrelated toxic species that have converged on the same warning coloration, and both benefit by learned avoidance from predators
- mullerian mimicry faciliates learned avoidance
how is mullerian mimicry different from batesian mimicry in terms of dynamics
in mullerian mimicry there is honest warning signals for mutual benefit of both of the species. from batesian, the true toxic model experiences negative consequences because of the fake model
