lec 19- selection in the wild Flashcards
who studied the natural selection of stickleback fish in Haida Gwaii, Canada in the 1980’s?
Dr Tom Reimchen
do the sticklebacks showcase adaptive radiation?
yes, selection and diversity in different lakes all from a marine ancestor
what is the one rare stickleback in Haida Gwaii’s Serendipity lake?
“Charlotte unarmoured stickleback”
is the unarmoured stickleback endemic and is the population stable?
-yes, it is endemic/restricted to three lakes and is an incipient species
-population appears to be stable, but due to being restricted, prone to threats
what is an incipient species?
a group of organisms that is close to becoming a new species
how did the marine ancestor of sticklebacks result in the forming of the new populations?
the marine ancestor invaded lakes during high sea levels, then evolved into many unique endemic populations
mutations to what gene in the marine ancestor of sticklebacks resulted in the evolved populations?
Eda gene which produced the new variations
how are the ages of lakes measured?
from radioactive dating of peat at the bottom of lakes which gives minimum age of how long the lakes have been in existence
how old were all the studied lakes in Haida Gwaii?
10 to 11,000 years old
where did sticklebacks with reduced or no bony armour plates on sides and small or missing spines live?
in small, shallow, boggy lakes with no fish or bird predators
where did sticklebacks with larger sizes and large strong pelvic and dorsal spines live?
on larger, deeper lakes like Drizzle and Mayer where trout and loon birds and other predators lived
how does sticklebacks armour protect from predators like the Loon?
the large spines that are locked into their bony skeleton are effective at making the sticklebacks bigger in diameter, and the sharp spines make it harder for predators to swallow
what evidence did Dr. Tom Reimchen have that proved that the sticklebacks can get away from predators with their bony armour?
He researched sticklebacks with aviscars on their bodies from bird beaks, indicating that they had escaped from predation
what is the tradeoff the no armour sticklebacks experience?
-dragonfly nymphs and diving beetle larvae can bite the bog lake sticklebacks and use spines as handles, hence why it was selected against
-instead they traded protection for earlier reproduction and more offspring
did Darwin know that all the specimen he collected were finches?
no, he paid little attention and didn’t realize they were all finches
who found out all the Galapagos specimens were finches?
British ornithologist Gould
what book had the only published illustration of Finch beaks by Darwin?
journal of Researches (1845)
do the Galapagos finches show signs of adaptive radiation?
yes, originally 13-14 species, now 18
what are the 7 differences in feeding seen in the Galapagos finches?
-seed eaters
-Flower feeder Finch
-Vampire Finch which drinks blood
-Cactus Finch which eats insects
-egg feeder
-leaf eater (unusual)
-parasite remover
which two people studied the Galapagos finches again for 40 years?
Peter and Rosemary Grant
what island did Peter and Rosemary Grant go to in the Galapagos to study the finches?
Daphne Major
what does variations in beak size influence?
influences efficiency at eating different types of seeds (size and hardest)
what gene regulates beak length?
-calmodulin
high expression = long
low expression = short
what gene regulates beak depth?
-Bmp4
high expression = wide and deeper beaks
low expression = narrow beaks
do offspring inherit beak morphology from parents?
yes, beak depth has high h^2
the drought in 1977 changed seed availability, how did this effect bird beaks?
-during the drought, more hard and woody fruits with seeds were available than soft seeds
-this favoured the survival of larger beaked birds
do closely related species that coexist in one area showcase different beak depth than when alone when competing for food?
yes, principle of competitive exclusion
what does beak size influence?
fitness
what does directional selection favor?
favors increases or decreases in the population means of a trait
what does stabilizing selection maintain at average values?
traits when conditions are stable
does the direction and strength of natural selection fluctuate due to environmental changes?
yes
